rocksdb/tools/db_stress.cc

//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
//  This source code is licensed under both the GPLv2 (found in the
//  COPYING file in the root directory) and Apache 2.0 License
//  (found in the LICENSE.Apache file in the root directory).
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
//
// The test uses an array to compare against values written to the database.
// Keys written to the array are in 1:1 correspondence to the actual values in
// the database according to the formula in the function GenerateValue.

// Space is reserved in the array from 0 to FLAGS_max_key and values are
// randomly written/deleted/read from those positions. During verification we
// compare all the positions in the array. To shorten/elongate the running
// time, you could change the settings: FLAGS_max_key, FLAGS_ops_per_thread,
// (sometimes also FLAGS_threads).
//
// NOTE that if FLAGS_test_batches_snapshots is set, the test will have
// different behavior. See comment of the flag for details.

#ifndef GFLAGS
#include <cstdio>
int main() {
  fprintf(stderr, "Please install gflags to run rocksdb tools\n");
  return 1;
}
#else

#ifndef __STDC_FORMAT_MACROS
#define __STDC_FORMAT_MACROS
#endif  // __STDC_FORMAT_MACROS

#include <fcntl.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <algorithm>
#include <chrono>
#include <exception>
#include <queue>
#include <thread>

#include "db/db_impl.h"
#include "db/version_set.h"
#include "hdfs/env_hdfs.h"
#include "monitoring/histogram.h"
#include "options/options_helper.h"
#include "port/port.h"
#include "rocksdb/cache.h"
#include "rocksdb/env.h"
#include "rocksdb/slice.h"
#include "rocksdb/slice_transform.h"
#include "rocksdb/statistics.h"
#include "rocksdb/utilities/db_ttl.h"
#include "rocksdb/utilities/options_util.h"
#include "rocksdb/utilities/transaction.h"
#include "rocksdb/utilities/transaction_db.h"
#include "rocksdb/write_batch.h"
#include "util/coding.h"
#include "util/compression.h"
#include "util/crc32c.h"
#include "util/gflags_compat.h"
#include "util/logging.h"
#include "util/mutexlock.h"
#include "util/random.h"
#include "util/string_util.h"
// SyncPoint is not supported in Released Windows Mode.
#if !(defined NDEBUG) || !defined(OS_WIN)
#include "util/sync_point.h"
#endif  // !(defined NDEBUG) || !defined(OS_WIN)
#include "util/testutil.h"

#include "utilities/merge_operators.h"

using GFLAGS_NAMESPACE::ParseCommandLineFlags;
using GFLAGS_NAMESPACE::RegisterFlagValidator;
using GFLAGS_NAMESPACE::SetUsageMessage;

static const long KB = 1024;
static const int kRandomValueMaxFactor = 3;
static const int kValueMaxLen = 100;

static bool ValidateUint32Range(const char* flagname, uint64_t value) {
  if (value > std::numeric_limits<uint32_t>::max()) {
    fprintf(stderr,
            "Invalid value for --%s: %lu, overflow\n",
            flagname,
            (unsigned long)value);
    return false;
  }
  return true;
}

DEFINE_uint64(seed, 2341234, "Seed for PRNG");
static const bool FLAGS_seed_dummy __attribute__((__unused__)) =
    RegisterFlagValidator(&FLAGS_seed, &ValidateUint32Range);

DEFINE_int64(max_key, 1 * KB* KB,
             "Max number of key/values to place in database");

DEFINE_int32(column_families, 10, "Number of column families");

DEFINE_string(
    options_file, "",
    "The path to a RocksDB options file.  If specified, then db_stress will "
    "run with the RocksDB options in the default column family of the "
    "specified options file. Note that, when an options file is provided, "
    "db_stress will ignore the flag values for all options that may be passed "
    "via options file.");

DEFINE_int64(
    active_width, 0,
    "Number of keys in active span of the key-range at any given time. The "
    "span begins with its left endpoint at key 0, gradually moves rightwards, "
    "and ends with its right endpoint at max_key. If set to 0, active_width "
    "will be sanitized to be equal to max_key.");

// TODO(noetzli) Add support for single deletes
DEFINE_bool(test_batches_snapshots, false,
            "If set, the test uses MultiGet(), MultiPut() and MultiDelete()"
            " which read/write/delete multiple keys in a batch. In this mode,"
            " we do not verify db content by comparing the content with the "
            "pre-allocated array. Instead, we do partial verification inside"
            " MultiGet() by checking various values in a batch. Benefit of"
            " this mode:\n"
            "\t(a) No need to acquire mutexes during writes (less cache "
            "flushes in multi-core leading to speed up)\n"
            "\t(b) No long validation at the end (more speed up)\n"
            "\t(c) Test snapshot and atomicity of batch writes");

DEFINE_int32(threads, 32, "Number of concurrent threads to run.");

DEFINE_int32(ttl, -1,
             "Opens the db with this ttl value if this is not -1. "
             "Carefully specify a large value such that verifications on "
             "deleted values don't fail");

DEFINE_int32(value_size_mult, 8,
             "Size of value will be this number times rand_int(1,3) bytes");

DEFINE_int32(compaction_readahead_size, 0, "Compaction readahead size");

DEFINE_bool(verify_before_write, false, "Verify before write");

DEFINE_bool(histogram, false, "Print histogram of operation timings");

DEFINE_bool(destroy_db_initially, true,
            "Destroys the database dir before start if this is true");

DEFINE_bool(verbose, false, "Verbose");

DEFINE_bool(progress_reports, true,
            "If true, db_stress will report number of finished operations");

DEFINE_uint64(db_write_buffer_size, rocksdb::Options().db_write_buffer_size,
              "Number of bytes to buffer in all memtables before compacting");

DEFINE_int32(write_buffer_size,
             static_cast<int32_t>(rocksdb::Options().write_buffer_size),
             "Number of bytes to buffer in memtable before compacting");

DEFINE_int32(max_write_buffer_number,
             rocksdb::Options().max_write_buffer_number,
             "The number of in-memory memtables. "
             "Each memtable is of size FLAGS_write_buffer_size.");

DEFINE_int32(min_write_buffer_number_to_merge,
             rocksdb::Options().min_write_buffer_number_to_merge,
             "The minimum number of write buffers that will be merged together "
             "before writing to storage. This is cheap because it is an "
             "in-memory merge. If this feature is not enabled, then all these "
             "write buffers are flushed to L0 as separate files and this "
             "increases read amplification because a get request has to check "
             "in all of these files. Also, an in-memory merge may result in "
             "writing less data to storage if there are duplicate records in"
             " each of these individual write buffers.");

DEFINE_int32(max_write_buffer_number_to_maintain,
             rocksdb::Options().max_write_buffer_number_to_maintain,
             "The total maximum number of write buffers to maintain in memory "
             "including copies of buffers that have already been flushed. "
             "Unlike max_write_buffer_number, this parameter does not affect "
             "flushing. This controls the minimum amount of write history "
             "that will be available in memory for conflict checking when "
             "Transactions are used. If this value is too low, some "
             "transactions may fail at commit time due to not being able to "
             "determine whether there were any write conflicts. Setting this "
             "value to 0 will cause write buffers to be freed immediately "
             "after they are flushed.  If this value is set to -1, "
             "'max_write_buffer_number' will be used.");

DEFINE_double(memtable_prefix_bloom_size_ratio,
              rocksdb::Options().memtable_prefix_bloom_size_ratio,
              "creates prefix blooms for memtables, each with size "
              "`write_buffer_size * memtable_prefix_bloom_size_ratio`.");

DEFINE_int32(open_files, rocksdb::Options().max_open_files,
             "Maximum number of files to keep open at the same time "
             "(use default if == 0)");

DEFINE_int64(compressed_cache_size, -1,
             "Number of bytes to use as a cache of compressed data."
             " Negative means use default settings.");

DEFINE_int32(compaction_style, rocksdb::Options().compaction_style, "");

DEFINE_int32(level0_file_num_compaction_trigger,
             rocksdb::Options().level0_file_num_compaction_trigger,
             "Level0 compaction start trigger");

DEFINE_int32(level0_slowdown_writes_trigger,
             rocksdb::Options().level0_slowdown_writes_trigger,
             "Number of files in level-0 that will slow down writes");

DEFINE_int32(level0_stop_writes_trigger,
             rocksdb::Options().level0_stop_writes_trigger,
             "Number of files in level-0 that will trigger put stop.");

DEFINE_int32(block_size,
             static_cast<int32_t>(rocksdb::BlockBasedTableOptions().block_size),
             "Number of bytes in a block.");

DEFINE_int32(max_background_compactions,
             rocksdb::Options().max_background_compactions,
             "The maximum number of concurrent background compactions "
             "that can occur in parallel.");

DEFINE_int32(num_bottom_pri_threads, 0,
             "The number of threads in the bottom-priority thread pool (used "
             "by universal compaction only).");

DEFINE_int32(compaction_thread_pool_adjust_interval, 0,
             "The interval (in milliseconds) to adjust compaction thread pool "
             "size. Don't change it periodically if the value is 0.");

DEFINE_int32(compaction_thread_pool_variations, 2,
             "Range of background thread pool size variations when adjusted "
             "periodically.");

DEFINE_int32(max_background_flushes, rocksdb::Options().max_background_flushes,
             "The maximum number of concurrent background flushes "
             "that can occur in parallel.");

DEFINE_int32(universal_size_ratio, 0, "The ratio of file sizes that trigger"
             " compaction in universal style");

DEFINE_int32(universal_min_merge_width, 0, "The minimum number of files to "
             "compact in universal style compaction");

DEFINE_int32(universal_max_merge_width, 0, "The max number of files to compact"
             " in universal style compaction");

DEFINE_int32(universal_max_size_amplification_percent, 0,
             "The max size amplification for universal style compaction");

DEFINE_int32(clear_column_family_one_in, 1000000,
             "With a chance of 1/N, delete a column family and then recreate "
             "it again. If N == 0, never drop/create column families. "
             "When test_batches_snapshots is true, this flag has no effect");

DEFINE_int32(set_options_one_in, 0,
             "With a chance of 1/N, change some random options");

DEFINE_int32(set_in_place_one_in, 0,
             "With a chance of 1/N, toggle in place support option");

DEFINE_int64(cache_size, 2LL * KB * KB * KB,
             "Number of bytes to use as a cache of uncompressed data.");

DEFINE_bool(use_clock_cache, false,
            "Replace default LRU block cache with clock cache.");

DEFINE_uint64(subcompactions, 1,
              "Maximum number of subcompactions to divide L0-L1 compactions "
              "into.");

DEFINE_bool(allow_concurrent_memtable_write, false,
            "Allow multi-writers to update mem tables in parallel.");

DEFINE_bool(enable_write_thread_adaptive_yield, true,
            "Use a yielding spin loop for brief writer thread waits.");

static const bool FLAGS_subcompactions_dummy __attribute__((__unused__)) =
    RegisterFlagValidator(&FLAGS_subcompactions, &ValidateUint32Range);

static bool ValidateInt32Positive(const char* flagname, int32_t value) {
  if (value < 0) {
    fprintf(stderr, "Invalid value for --%s: %d, must be >=0\n",
            flagname, value);
    return false;
  }
  return true;
}
DEFINE_int32(reopen, 10, "Number of times database reopens");
static const bool FLAGS_reopen_dummy __attribute__((__unused__)) =
    RegisterFlagValidator(&FLAGS_reopen, &ValidateInt32Positive);

DEFINE_int32(bloom_bits, 10, "Bloom filter bits per key. "
             "Negative means use default settings.");

DEFINE_bool(use_block_based_filter, false, "use block based filter"
              "instead of full filter for block based table");

DEFINE_string(db, "", "Use the db with the following name.");

DEFINE_string(
    expected_values_path, "",
    "File where the array of expected uint32_t values will be stored. If "
    "provided and non-empty, the DB state will be verified against these "
    "values after recovery. --max_key and --column_family must be kept the "
    "same across invocations of this program that use the same "
    "--expected_values_path.");

DEFINE_bool(verify_checksum, false,
            "Verify checksum for every block read from storage");

DEFINE_bool(mmap_read, rocksdb::Options().allow_mmap_reads,
            "Allow reads to occur via mmap-ing files");

DEFINE_bool(mmap_write, rocksdb::Options().allow_mmap_writes,
            "Allow writes to occur via mmap-ing files");

DEFINE_bool(use_direct_reads, rocksdb::Options().use_direct_reads,
            "Use O_DIRECT for reading data");

DEFINE_bool(use_direct_io_for_flush_and_compaction,
            rocksdb::Options().use_direct_io_for_flush_and_compaction,
            "Use O_DIRECT for writing data");

// Database statistics
static std::shared_ptr<rocksdb::Statistics> dbstats;
DEFINE_bool(statistics, false, "Create database statistics");

DEFINE_bool(sync, false, "Sync all writes to disk");

DEFINE_bool(use_fsync, false, "If true, issue fsync instead of fdatasync");

DEFINE_int32(kill_random_test, 0,
             "If non-zero, kill at various points in source code with "
             "probability 1/this");
static const bool FLAGS_kill_random_test_dummy __attribute__((__unused__)) =
    RegisterFlagValidator(&FLAGS_kill_random_test, &ValidateInt32Positive);
extern int rocksdb_kill_odds;

DEFINE_string(kill_prefix_blacklist, "",
              "If non-empty, kill points with prefix in the list given will be"
              " skipped. Items are comma-separated.");
extern std::vector<std::string> rocksdb_kill_prefix_blacklist;

DEFINE_bool(disable_wal, false, "If true, do not write WAL for write.");

DEFINE_int64(target_file_size_base, rocksdb::Options().target_file_size_base,
             "Target level-1 file size for compaction");

DEFINE_int32(target_file_size_multiplier, 1,
             "A multiplier to compute target level-N file size (N >= 2)");

DEFINE_uint64(max_bytes_for_level_base,
              rocksdb::Options().max_bytes_for_level_base,
              "Max bytes for level-1");

DEFINE_double(max_bytes_for_level_multiplier, 2,
              "A multiplier to compute max bytes for level-N (N >= 2)");

DEFINE_int32(range_deletion_width, 10,
             "The width of the range deletion intervals.");

DEFINE_uint64(rate_limiter_bytes_per_sec, 0, "Set options.rate_limiter value.");

DEFINE_bool(rate_limit_bg_reads, false,
            "Use options.rate_limiter on compaction reads");

DEFINE_bool(use_txn, false,
            "Use TransactionDB. Currently the default write policy is "
            "TxnDBWritePolicy::WRITE_PREPARED");

// Temporarily disable this to allows it to detect new bugs
DEFINE_int32(compact_files_one_in, 0,
             "If non-zero, then CompactFiles() will be called one for every N "
             "operations IN AVERAGE.  0 indicates CompactFiles() is disabled.");

DEFINE_int32(acquire_snapshot_one_in, 0,
             "If non-zero, then acquires a snapshot once every N operations on "
             "average.");

DEFINE_uint64(snapshot_hold_ops, 0,
              "If non-zero, then releases snapshots N operations after they're "
              "acquired.");

static bool ValidateInt32Percent(const char* flagname, int32_t value) {
  if (value < 0 || value>100) {
    fprintf(stderr, "Invalid value for --%s: %d, 0<= pct <=100 \n",
            flagname, value);
    return false;
  }
  return true;
}

DEFINE_int32(readpercent, 10,
             "Ratio of reads to total workload (expressed as a percentage)");
static const bool FLAGS_readpercent_dummy __attribute__((__unused__)) =
    RegisterFlagValidator(&FLAGS_readpercent, &ValidateInt32Percent);

DEFINE_int32(prefixpercent, 20,
             "Ratio of prefix iterators to total workload (expressed as a"
             " percentage)");
static const bool FLAGS_prefixpercent_dummy __attribute__((__unused__)) =
    RegisterFlagValidator(&FLAGS_prefixpercent, &ValidateInt32Percent);

DEFINE_int32(writepercent, 45,
             "Ratio of writes to total workload (expressed as a percentage)");
static const bool FLAGS_writepercent_dummy __attribute__((__unused__)) =
    RegisterFlagValidator(&FLAGS_writepercent, &ValidateInt32Percent);

DEFINE_int32(delpercent, 15,
             "Ratio of deletes to total workload (expressed as a percentage)");
static const bool FLAGS_delpercent_dummy __attribute__((__unused__)) =
    RegisterFlagValidator(&FLAGS_delpercent, &ValidateInt32Percent);

DEFINE_int32(delrangepercent, 0,
             "Ratio of range deletions to total workload (expressed as a "
             "percentage). Cannot be used with test_batches_snapshots");
static const bool FLAGS_delrangepercent_dummy __attribute__((__unused__)) =
    RegisterFlagValidator(&FLAGS_delrangepercent, &ValidateInt32Percent);

DEFINE_int32(nooverwritepercent, 60,
             "Ratio of keys without overwrite to total workload (expressed as "
             " a percentage)");
static const bool FLAGS_nooverwritepercent_dummy __attribute__((__unused__)) =
    RegisterFlagValidator(&FLAGS_nooverwritepercent, &ValidateInt32Percent);

DEFINE_int32(iterpercent, 10, "Ratio of iterations to total workload"
             " (expressed as a percentage)");
static const bool FLAGS_iterpercent_dummy __attribute__((__unused__)) =
    RegisterFlagValidator(&FLAGS_iterpercent, &ValidateInt32Percent);

DEFINE_uint64(num_iterations, 10, "Number of iterations per MultiIterate run");
static const bool FLAGS_num_iterations_dummy __attribute__((__unused__)) =
    RegisterFlagValidator(&FLAGS_num_iterations, &ValidateUint32Range);

namespace {
enum rocksdb::CompressionType StringToCompressionType(const char* ctype) {
  assert(ctype);

  if (!strcasecmp(ctype, "none"))
    return rocksdb::kNoCompression;
  else if (!strcasecmp(ctype, "snappy"))
    return rocksdb::kSnappyCompression;
  else if (!strcasecmp(ctype, "zlib"))
    return rocksdb::kZlibCompression;
  else if (!strcasecmp(ctype, "bzip2"))
    return rocksdb::kBZip2Compression;
  else if (!strcasecmp(ctype, "lz4"))
    return rocksdb::kLZ4Compression;
  else if (!strcasecmp(ctype, "lz4hc"))
    return rocksdb::kLZ4HCCompression;
  else if (!strcasecmp(ctype, "xpress"))
    return rocksdb::kXpressCompression;
  else if (!strcasecmp(ctype, "zstd"))
    return rocksdb::kZSTD;

  fprintf(stderr, "Cannot parse compression type '%s'\n", ctype);
  return rocksdb::kSnappyCompression; //default value
}

enum rocksdb::ChecksumType StringToChecksumType(const char* ctype) {
  assert(ctype);
  auto iter = rocksdb::checksum_type_string_map.find(ctype);
  if (iter != rocksdb::checksum_type_string_map.end()) {
    return iter->second;
  }
  fprintf(stderr, "Cannot parse checksum type '%s'\n", ctype);
  return rocksdb::kCRC32c;
}

std::string ChecksumTypeToString(rocksdb::ChecksumType ctype) {
  auto iter = std::find_if(
      rocksdb::checksum_type_string_map.begin(),
      rocksdb::checksum_type_string_map.end(),
      [&](const std::pair<std::string, rocksdb::ChecksumType>&
              name_and_enum_val) { return name_and_enum_val.second == ctype; });
  assert(iter != rocksdb::checksum_type_string_map.end());
  return iter->first;
}

std::vector<std::string> SplitString(std::string src) {
  std::vector<std::string> ret;
  if (src.empty()) {
    return ret;
  }
  size_t pos = 0;
  size_t pos_comma;
  while ((pos_comma = src.find(',', pos)) != std::string::npos) {
    ret.push_back(src.substr(pos, pos_comma - pos));
    pos = pos_comma + 1;
  }
  ret.push_back(src.substr(pos, src.length()));
  return ret;
}
}  // namespace

DEFINE_string(compression_type, "snappy",
              "Algorithm to use to compress the database");
static enum rocksdb::CompressionType FLAGS_compression_type_e =
    rocksdb::kSnappyCompression;

DEFINE_string(checksum_type, "kCRC32c", "Algorithm to use to checksum blocks");
static enum rocksdb::ChecksumType FLAGS_checksum_type_e = rocksdb::kCRC32c;

DEFINE_string(hdfs, "", "Name of hdfs environment");
// posix or hdfs environment
static rocksdb::Env* FLAGS_env = rocksdb::Env::Default();

DEFINE_uint64(ops_per_thread, 1200000, "Number of operations per thread.");
static const bool FLAGS_ops_per_thread_dummy __attribute__((__unused__)) =
    RegisterFlagValidator(&FLAGS_ops_per_thread, &ValidateUint32Range);

DEFINE_uint64(log2_keys_per_lock, 2, "Log2 of number of keys per lock");
static const bool FLAGS_log2_keys_per_lock_dummy __attribute__((__unused__)) =
    RegisterFlagValidator(&FLAGS_log2_keys_per_lock, &ValidateUint32Range);

DEFINE_uint64(max_manifest_file_size, 16384, "Maximum size of a MANIFEST file");

DEFINE_bool(in_place_update, false, "On true, does inplace update in memtable");

enum RepFactory {
  kSkipList,
  kHashSkipList,
  kVectorRep
};

namespace {
enum RepFactory StringToRepFactory(const char* ctype) {
  assert(ctype);

  if (!strcasecmp(ctype, "skip_list"))
    return kSkipList;
  else if (!strcasecmp(ctype, "prefix_hash"))
    return kHashSkipList;
  else if (!strcasecmp(ctype, "vector"))
    return kVectorRep;

  fprintf(stdout, "Cannot parse memreptable %s\n", ctype);
  return kSkipList;
}
}  // namespace

static enum RepFactory FLAGS_rep_factory;
DEFINE_string(memtablerep, "prefix_hash", "");

static bool ValidatePrefixSize(const char* flagname, int32_t value) {
  if (value < 0 || value > 8) {
    fprintf(stderr, "Invalid value for --%s: %d. 0 <= PrefixSize <= 8\n",
            flagname, value);
    return false;
  }
  return true;
}
DEFINE_int32(prefix_size, 7, "Control the prefix size for HashSkipListRep");
static const bool FLAGS_prefix_size_dummy __attribute__((__unused__)) =
    RegisterFlagValidator(&FLAGS_prefix_size, &ValidatePrefixSize);

DEFINE_bool(use_merge, false, "On true, replaces all writes with a Merge "
            "that behaves like a Put");

DEFINE_bool(use_full_merge_v1, false,
            "On true, use a merge operator that implement the deprecated "
            "version of FullMerge");

namespace rocksdb {

// convert long to a big-endian slice key
static std::string Key(int64_t val) {
  std::string little_endian_key;
  std::string big_endian_key;
  PutFixed64(&little_endian_key, val);
  assert(little_endian_key.size() == sizeof(val));
  big_endian_key.resize(sizeof(val));
  for (size_t i = 0 ; i < sizeof(val); ++i) {
    big_endian_key[i] = little_endian_key[sizeof(val) - 1 - i];
  }
  return big_endian_key;
}

static std::string StringToHex(const std::string& str) {
  std::string result = "0x";
  result.append(Slice(str).ToString(true));
  return result;
}


class StressTest;
namespace {

class Stats {
 private:
  uint64_t start_;
  uint64_t finish_;
  double  seconds_;
  long done_;
  long gets_;
  long prefixes_;
  long writes_;
  long deletes_;
  size_t single_deletes_;
  long iterator_size_sums_;
  long founds_;
  long iterations_;
  long range_deletions_;
  long covered_by_range_deletions_;
  long errors_;
  long num_compact_files_succeed_;
  long num_compact_files_failed_;
  int next_report_;
  size_t bytes_;
  uint64_t last_op_finish_;
  HistogramImpl hist_;

 public:
  Stats() { }

  void Start() {
    next_report_ = 100;
    hist_.Clear();
    done_ = 0;
    gets_ = 0;
    prefixes_ = 0;
    writes_ = 0;
    deletes_ = 0;
    single_deletes_ = 0;
    iterator_size_sums_ = 0;
    founds_ = 0;
    iterations_ = 0;
    range_deletions_ = 0;
    covered_by_range_deletions_ = 0;
    errors_ = 0;
    bytes_ = 0;
    seconds_ = 0;
    num_compact_files_succeed_ = 0;
    num_compact_files_failed_ = 0;
    start_ = FLAGS_env->NowMicros();
    last_op_finish_ = start_;
    finish_ = start_;
  }

  void Merge(const Stats& other) {
    hist_.Merge(other.hist_);
    done_ += other.done_;
    gets_ += other.gets_;
    prefixes_ += other.prefixes_;
    writes_ += other.writes_;
    deletes_ += other.deletes_;
    single_deletes_ += other.single_deletes_;
    iterator_size_sums_ += other.iterator_size_sums_;
    founds_ += other.founds_;
    iterations_ += other.iterations_;
    range_deletions_ += other.range_deletions_;
    covered_by_range_deletions_ = other.covered_by_range_deletions_;
    errors_ += other.errors_;
    bytes_ += other.bytes_;
    seconds_ += other.seconds_;
    num_compact_files_succeed_ += other.num_compact_files_succeed_;
    num_compact_files_failed_ += other.num_compact_files_failed_;
    if (other.start_ < start_) start_ = other.start_;
    if (other.finish_ > finish_) finish_ = other.finish_;
  }

  void Stop() {
    finish_ = FLAGS_env->NowMicros();
    seconds_ = (finish_ - start_) * 1e-6;
  }

  void FinishedSingleOp() {
    if (FLAGS_histogram) {
      auto now = FLAGS_env->NowMicros();
      auto micros = now - last_op_finish_;
      hist_.Add(micros);
      if (micros > 20000) {
        fprintf(stdout, "long op: %" PRIu64 " micros%30s\r", micros, "");
      }
      last_op_finish_ = now;
    }

      done_++;
    if (FLAGS_progress_reports) {
      if (done_ >= next_report_) {
        if      (next_report_ < 1000)   next_report_ += 100;
        else if (next_report_ < 5000)   next_report_ += 500;
        else if (next_report_ < 10000)  next_report_ += 1000;
        else if (next_report_ < 50000)  next_report_ += 5000;
        else if (next_report_ < 100000) next_report_ += 10000;
        else if (next_report_ < 500000) next_report_ += 50000;
        else                            next_report_ += 100000;
        fprintf(stdout, "... finished %ld ops%30s\r", done_, "");
      }
    }
  }

  void AddBytesForWrites(int nwrites, size_t nbytes) {
    writes_ += nwrites;
    bytes_ += nbytes;
  }

  void AddGets(int ngets, int nfounds) {
    founds_ += nfounds;
    gets_ += ngets;
  }

  void AddPrefixes(int nprefixes, int count) {
    prefixes_ += nprefixes;
    iterator_size_sums_ += count;
  }

  void AddIterations(int n) {
    iterations_ += n;
  }

  void AddDeletes(int n) {
    deletes_ += n;
  }

  void AddSingleDeletes(size_t n) { single_deletes_ += n; }

  void AddRangeDeletions(int n) {
    range_deletions_ += n;
  }

  void AddCoveredByRangeDeletions(int n) {
    covered_by_range_deletions_ += n;
  }

  void AddErrors(int n) {
    errors_ += n;
  }

  void AddNumCompactFilesSucceed(int n) { num_compact_files_succeed_ += n; }

  void AddNumCompactFilesFailed(int n) { num_compact_files_failed_ += n; }

  void Report(const char* name) {
    std::string extra;
    if (bytes_ < 1 || done_ < 1) {
      fprintf(stderr, "No writes or ops?\n");
      return;
    }

    double elapsed = (finish_ - start_) * 1e-6;
    double bytes_mb = bytes_ / 1048576.0;
    double rate = bytes_mb / elapsed;
    double throughput = (double)done_/elapsed;

    fprintf(stdout, "%-12s: ", name);
    fprintf(stdout, "%.3f micros/op %ld ops/sec\n",
            seconds_ * 1e6 / done_, (long)throughput);
    fprintf(stdout, "%-12s: Wrote %.2f MB (%.2f MB/sec) (%ld%% of %ld ops)\n",
            "", bytes_mb, rate, (100*writes_)/done_, done_);
    fprintf(stdout, "%-12s: Wrote %ld times\n", "", writes_);
    fprintf(stdout, "%-12s: Deleted %ld times\n", "", deletes_);
    fprintf(stdout, "%-12s: Single deleted %" ROCKSDB_PRIszt " times\n", "",
           single_deletes_);
    fprintf(stdout, "%-12s: %ld read and %ld found the key\n", "",
            gets_, founds_);
    fprintf(stdout, "%-12s: Prefix scanned %ld times\n", "", prefixes_);
    fprintf(stdout, "%-12s: Iterator size sum is %ld\n", "",
            iterator_size_sums_);
    fprintf(stdout, "%-12s: Iterated %ld times\n", "", iterations_);
    fprintf(stdout, "%-12s: Deleted %ld key-ranges\n", "", range_deletions_);
    fprintf(stdout, "%-12s: Range deletions covered %ld keys\n", "",
            covered_by_range_deletions_);

    fprintf(stdout, "%-12s: Got errors %ld times\n", "", errors_);
    fprintf(stdout, "%-12s: %ld CompactFiles() succeed\n", "",
            num_compact_files_succeed_);
    fprintf(stdout, "%-12s: %ld CompactFiles() did not succeed\n", "",
            num_compact_files_failed_);

    if (FLAGS_histogram) {
      fprintf(stdout, "Microseconds per op:\n%s\n", hist_.ToString().c_str());
    }
    fflush(stdout);
  }
};

// State shared by all concurrent executions of the same benchmark.
class SharedState {
 public:
  // indicates a key may have any value (or not be present) as an operation on
  // it is incomplete.
  static const uint32_t UNKNOWN_SENTINEL;
  // indicates a key should definitely be deleted
  static const uint32_t DELETION_SENTINEL;

  explicit SharedState(StressTest* stress_test)
      : cv_(&mu_),
        seed_(static_cast<uint32_t>(FLAGS_seed)),
        max_key_(FLAGS_max_key),
        log2_keys_per_lock_(static_cast<uint32_t>(FLAGS_log2_keys_per_lock)),
        num_threads_(FLAGS_threads),
        num_initialized_(0),
        num_populated_(0),
        vote_reopen_(0),
        num_done_(0),
        start_(false),
        start_verify_(false),
        should_stop_bg_thread_(false),
        bg_thread_finished_(false),
        stress_test_(stress_test),
        verification_failure_(false),
        no_overwrite_ids_(FLAGS_column_families),
        values_(nullptr) {
    // Pick random keys in each column family that will not experience
    // overwrite

    printf("Choosing random keys with no overwrite\n");
    Random64 rnd(seed_);
    // Start with the identity permutation. Subsequent iterations of
    // for loop below will start with perm of previous for loop
    int64_t *permutation = new int64_t[max_key_];
    for (int64_t i = 0; i < max_key_; i++) {
      permutation[i] = i;
    }

    for (auto& cf_ids : no_overwrite_ids_) {
      // Now do the Knuth shuffle
      int64_t num_no_overwrite_keys = (max_key_ * FLAGS_nooverwritepercent) / 100;
      // Only need to figure out first num_no_overwrite_keys of permutation
      for (int64_t i = 0; i < num_no_overwrite_keys; i++) {
        int64_t rand_index = i + rnd.Next() % (max_key_ - 1 - i);
        // Swap i and rand_index;
        int64_t temp = permutation[i];
        permutation[i] = permutation[rand_index];
        permutation[rand_index] = temp;
      }

      // Now fill cf_ids with the first num_no_overwrite_keys of permutation
      cf_ids.reserve(num_no_overwrite_keys);
      for (int64_t i = 0; i < num_no_overwrite_keys; i++) {
        cf_ids.insert(permutation[i]);
      }
      assert(cf_ids.size() == static_cast<size_t>(num_no_overwrite_keys));
    }
    delete[] permutation;

    size_t expected_values_size =
        sizeof(std::atomic<uint32_t>) * FLAGS_column_families * max_key_;
    bool values_init_needed = false;
    Status status;
    if (!FLAGS_expected_values_path.empty()) {
      if (!std::atomic<uint32_t>{}.is_lock_free()) {
        status = Status::InvalidArgument(
            "Cannot use --expected_values_path on platforms without lock-free "
            "std::atomic<uint32_t>");
      }
      if (status.ok() && FLAGS_clear_column_family_one_in > 0) {
        status = Status::InvalidArgument(
            "Cannot use --expected_values_path on when "
            "--clear_column_family_one_in is greater than zero.");
      }
      uint64_t size = 0;
      if (status.ok()) {
        status = FLAGS_env->GetFileSize(FLAGS_expected_values_path, &size);
      }
      unique_ptr<WritableFile> wfile;
      if (status.ok() && size == 0) {
        const EnvOptions soptions;
        status = FLAGS_env->NewWritableFile(FLAGS_expected_values_path, &wfile,
                                            soptions);
      }
      if (status.ok() && size == 0) {
        std::string buf(expected_values_size, '\0');
        status = wfile->Append(buf);
        values_init_needed = true;
      }
      if (status.ok()) {
        status = FLAGS_env->NewMemoryMappedFileBuffer(
            FLAGS_expected_values_path, &expected_mmap_buffer_);
      }
      if (status.ok()) {
        assert(expected_mmap_buffer_->GetLen() == expected_values_size);
        values_ =
            static_cast<std::atomic<uint32_t>*>(expected_mmap_buffer_->GetBase());
        assert(values_ != nullptr);
      } else {
        fprintf(stderr, "Failed opening shared file '%s' with error: %s\n",
                FLAGS_expected_values_path.c_str(), status.ToString().c_str());
        assert(values_ == nullptr);
      }
    }
    if (values_ == nullptr) {
      values_allocation_.reset(
          new std::atomic<uint32_t>[FLAGS_column_families * max_key_]);
      values_ = &values_allocation_[0];
      values_init_needed = true;
    }
    assert(values_ != nullptr);
    if (values_init_needed) {
      for (int i = 0; i < FLAGS_column_families; ++i) {
        for (int j = 0; j < max_key_; ++j) {
          Delete(i, j, false /* pending */);
        }
      }
    }

    if (FLAGS_test_batches_snapshots) {
      fprintf(stdout, "No lock creation because test_batches_snapshots set\n");
      return;
    }

    long num_locks = static_cast<long>(max_key_ >> log2_keys_per_lock_);
    if (max_key_ & ((1 << log2_keys_per_lock_) - 1)) {
      num_locks++;
    }
    fprintf(stdout, "Creating %ld locks\n", num_locks * FLAGS_column_families);
    key_locks_.resize(FLAGS_column_families);

    for (int i = 0; i < FLAGS_column_families; ++i) {
      key_locks_[i].resize(num_locks);
      for (auto& ptr : key_locks_[i]) {
        ptr.reset(new port::Mutex);
      }
    }
  }

  ~SharedState() {}

  port::Mutex* GetMutex() {
    return &mu_;
  }

  port::CondVar* GetCondVar() {
    return &cv_;
  }

  StressTest* GetStressTest() const {
    return stress_test_;
  }

  int64_t GetMaxKey() const {
    return max_key_;
  }

  uint32_t GetNumThreads() const {
    return num_threads_;
  }

  void IncInitialized() {
    num_initialized_++;
  }

  void IncOperated() {
    num_populated_++;
  }

  void IncDone() {
    num_done_++;
  }

  void IncVotedReopen() {
    vote_reopen_ = (vote_reopen_ + 1) % num_threads_;
  }

  bool AllInitialized() const {
    return num_initialized_ >= num_threads_;
  }

  bool AllOperated() const {
    return num_populated_ >= num_threads_;
  }

  bool AllDone() const {
    return num_done_ >= num_threads_;
  }

  bool AllVotedReopen() {
    return (vote_reopen_ == 0);
  }

  void SetStart() {
    start_ = true;
  }

  void SetStartVerify() {
    start_verify_ = true;
  }

  bool Started() const {
    return start_;
  }

  bool VerifyStarted() const {
    return start_verify_;
  }

  void SetVerificationFailure() { verification_failure_.store(true); }

  bool HasVerificationFailedYet() { return verification_failure_.load(); }

  port::Mutex* GetMutexForKey(int cf, int64_t key) {
    return key_locks_[cf][key >> log2_keys_per_lock_].get();
  }

  void LockColumnFamily(int cf) {
    for (auto& mutex : key_locks_[cf]) {
      mutex->Lock();
    }
  }

  void UnlockColumnFamily(int cf) {
    for (auto& mutex : key_locks_[cf]) {
      mutex->Unlock();
    }
  }

  std::atomic<uint32_t>& Value(int cf, int64_t key) const {
    return values_[cf * max_key_ + key];
  }

  void ClearColumnFamily(int cf) {
    std::fill(&Value(cf, 0 /* key */), &Value(cf + 1, 0 /* key */),
              DELETION_SENTINEL);
  }

  // @param pending True if the update may have started but is not yet
  //    guaranteed finished. This is useful for crash-recovery testing when the
  //    process may crash before updating the expected values array.
  void Put(int cf, int64_t key, uint32_t value_base, bool pending) {
    if (!pending) {
      // prevent expected-value update from reordering before Write
      std::atomic_thread_fence(std::memory_order_release);
    }
    Value(cf, key).store(pending ? UNKNOWN_SENTINEL : value_base,
                         std::memory_order_relaxed);
    if (pending) {
      // prevent Write from reordering before expected-value update
      std::atomic_thread_fence(std::memory_order_release);
    }
  }

  uint32_t Get(int cf, int64_t key) const { return Value(cf, key); }

  // @param pending See comment above Put()
  // Returns true if the key was not yet deleted.
  bool Delete(int cf, int64_t key, bool pending) {
    if (Value(cf, key) == DELETION_SENTINEL) {
      return false;
    }
    Put(cf, key, DELETION_SENTINEL, pending);
    return true;
  }

  // @param pending See comment above Put()
  // Returns true if the key was not yet deleted.
  bool SingleDelete(int cf, int64_t key, bool pending) {
    return Delete(cf, key, pending);
  }

  // @param pending See comment above Put()
  // Returns number of keys deleted by the call.
  int DeleteRange(int cf, int64_t begin_key, int64_t end_key, bool pending) {
    int covered = 0;
    for (int64_t key = begin_key; key < end_key; ++key) {
      if (Delete(cf, key, pending)) {
        ++covered;
      }
    }
    return covered;
  }

  bool AllowsOverwrite(int cf, int64_t key) {
    return no_overwrite_ids_[cf].find(key) == no_overwrite_ids_[cf].end();
  }

  bool Exists(int cf, int64_t key) {
    // UNKNOWN_SENTINEL counts as exists. That assures a key for which overwrite
    // is disallowed can't be accidentally added a second time, in which case
    // SingleDelete wouldn't be able to properly delete the key. It does allow
    // the case where a SingleDelete might be added which covers nothing, but
    // that's not a correctness issue.
    uint32_t expected_value = Value(cf, key).load();
    return expected_value != DELETION_SENTINEL;
  }

  uint32_t GetSeed() const { return seed_; }

  void SetShouldStopBgThread() { should_stop_bg_thread_ = true; }

  bool ShoudStopBgThread() { return should_stop_bg_thread_; }

  void SetBgThreadFinish() { bg_thread_finished_ = true; }

  bool BgThreadFinished() const { return bg_thread_finished_; }

  bool ShouldVerifyAtBeginning() const {
    return expected_mmap_buffer_.get() != nullptr;
  }

 private:
  port::Mutex mu_;
  port::CondVar cv_;
  const uint32_t seed_;
  const int64_t max_key_;
  const uint32_t log2_keys_per_lock_;
  const int num_threads_;
  long num_initialized_;
  long num_populated_;
  long vote_reopen_;
  long num_done_;
  bool start_;
  bool start_verify_;
  bool should_stop_bg_thread_;
  bool bg_thread_finished_;
  StressTest* stress_test_;
  std::atomic<bool> verification_failure_;

  // Keys that should not be overwritten
  std::vector<std::unordered_set<size_t> > no_overwrite_ids_;

  std::atomic<uint32_t>* values_;
  std::unique_ptr<std::atomic<uint32_t>[]> values_allocation_;
  // Has to make it owned by a smart ptr as port::Mutex is not copyable
  // and storing it in the container may require copying depending on the impl.
  std::vector<std::vector<std::unique_ptr<port::Mutex> > > key_locks_;
  std::unique_ptr<MemoryMappedFileBuffer> expected_mmap_buffer_;
};

const uint32_t SharedState::UNKNOWN_SENTINEL = 0xfffffffe;
const uint32_t SharedState::DELETION_SENTINEL = 0xffffffff;

// Per-thread state for concurrent executions of the same benchmark.
struct ThreadState {
  uint32_t tid;  // 0..n-1
  Random rand;   // Has different seeds for different threads
  SharedState* shared;
  Stats stats;
  struct SnapshotState {
    const Snapshot* snapshot;
    // The cf from which we did a Get at this snapshot
    int cf_at;
    // The name of the cf at the time that we did a read
    std::string cf_at_name;
    // The key with which we did a Get at this snapshot
    std::string key;
    // The status of the Get
    Status status;
    // The value of the Get
    std::string value;
  };
  std::queue<std::pair<uint64_t, SnapshotState> > snapshot_queue;

  ThreadState(uint32_t index, SharedState* _shared)
      : tid(index), rand(1000 + index + _shared->GetSeed()), shared(_shared) {}
};

class DbStressListener : public EventListener {
 public:
  DbStressListener(const std::string& db_name,
                   const std::vector<DbPath>& db_paths,
                   const std::vector<ColumnFamilyDescriptor>& column_families)
      : db_name_(db_name), db_paths_(db_paths),
        column_families_(column_families) {}
  virtual ~DbStressListener() {}
#ifndef ROCKSDB_LITE
  virtual void OnFlushCompleted(DB* /*db*/, const FlushJobInfo& info) override {
    assert(IsValidColumnFamilyName(info.cf_name));
    VerifyFilePath(info.file_path);
    // pretending doing some work here
    std::this_thread::sleep_for(
        std::chrono::microseconds(Random::GetTLSInstance()->Uniform(5000)));
  }

  virtual void OnCompactionCompleted(DB* /*db*/,
                                     const CompactionJobInfo& ci) override {
    assert(IsValidColumnFamilyName(ci.cf_name));
    assert(ci.input_files.size() + ci.output_files.size() > 0U);
    for (const auto& file_path : ci.input_files) {
      VerifyFilePath(file_path);
    }
    for (const auto& file_path : ci.output_files) {
      VerifyFilePath(file_path);
    }
    // pretending doing some work here
    std::this_thread::sleep_for(
        std::chrono::microseconds(Random::GetTLSInstance()->Uniform(5000)));
  }

  virtual void OnTableFileCreated(const TableFileCreationInfo& info) override {
    assert(info.db_name == db_name_);
    assert(IsValidColumnFamilyName(info.cf_name));
    VerifyFilePath(info.file_path);
    assert(info.job_id > 0 || FLAGS_compact_files_one_in > 0);
    if (info.status.ok()) {
      assert(info.file_size > 0);
      assert(info.table_properties.data_size > 0);
      assert(info.table_properties.raw_key_size > 0);
      assert(info.table_properties.num_entries > 0);
    }
  }

 protected:
  bool IsValidColumnFamilyName(const std::string& cf_name) const {
    if (cf_name == kDefaultColumnFamilyName) {
      return true;
    }
    // The column family names in the stress tests are numbers.
    for (size_t i = 0; i < cf_name.size(); ++i) {
      if (cf_name[i] < '0' || cf_name[i] > '9') {
        return false;
      }
    }
    return true;
  }

  void VerifyFileDir(const std::string& file_dir) {
#ifndef NDEBUG
    if (db_name_ == file_dir) {
      return;
    }
    for (const auto& db_path : db_paths_) {
      if (db_path.path == file_dir) {
        return;
      }
    }
    for (auto& cf : column_families_) {
      for (const auto& cf_path : cf.options.cf_paths) {
        if (cf_path.path == file_dir) {
            return;
        }
      }
    }
    assert(false);
#else
    (void)file_dir;
#endif  // !NDEBUG
  }

  void VerifyFileName(const std::string& file_name) {
#ifndef NDEBUG
    uint64_t file_number;
    FileType file_type;
    bool result = ParseFileName(file_name, &file_number, &file_type);
    assert(result);
    assert(file_type == kTableFile);
#else
    (void)file_name;
#endif  // !NDEBUG
  }

  void VerifyFilePath(const std::string& file_path) {
#ifndef NDEBUG
    size_t pos = file_path.find_last_of("/");
    if (pos == std::string::npos) {
      VerifyFileName(file_path);
    } else {
      if (pos > 0) {
        VerifyFileDir(file_path.substr(0, pos));
      }
      VerifyFileName(file_path.substr(pos));
    }
#else
    (void)file_path;
#endif  // !NDEBUG
  }
#endif  // !ROCKSDB_LITE

 private:
  std::string db_name_;
  std::vector<DbPath> db_paths_;
  std::vector<ColumnFamilyDescriptor> column_families_;
};

}  // namespace

class StressTest {
 public:
  StressTest()
      : cache_(NewCache(FLAGS_cache_size)),
        compressed_cache_(NewLRUCache(FLAGS_compressed_cache_size)),
        filter_policy_(FLAGS_bloom_bits >= 0
                           ? FLAGS_use_block_based_filter
                                 ? NewBloomFilterPolicy(FLAGS_bloom_bits, true)
                                 : NewBloomFilterPolicy(FLAGS_bloom_bits, false)
                           : nullptr),
        db_(nullptr),
#ifndef ROCKSDB_LITE
        txn_db_(nullptr),
#endif
        new_column_family_name_(1),
        num_times_reopened_(0) {
    if (FLAGS_destroy_db_initially) {
      std::vector<std::string> files;
      FLAGS_env->GetChildren(FLAGS_db, &files);
      for (unsigned int i = 0; i < files.size(); i++) {
        if (Slice(files[i]).starts_with("heap-")) {
          FLAGS_env->DeleteFile(FLAGS_db + "/" + files[i]);
        }
      }
      DestroyDB(FLAGS_db, Options());
    }
  }

  ~StressTest() {
    for (auto cf : column_families_) {
      delete cf;
    }
    column_families_.clear();
    delete db_;
  }

  std::shared_ptr<Cache> NewCache(size_t capacity) {
    if (capacity <= 0) {
      return nullptr;
    }
    if (FLAGS_use_clock_cache) {
      auto cache = NewClockCache((size_t)capacity);
      if (!cache) {
        fprintf(stderr, "Clock cache not supported.");
        exit(1);
      }
      return cache;
    } else {
      return NewLRUCache((size_t)capacity);
    }
  }

  bool BuildOptionsTable() {
    if (FLAGS_set_options_one_in <= 0) {
      return true;
    }

    std::unordered_map<std::string, std::vector<std::string> > options_tbl = {
        {"write_buffer_size",
         {ToString(options_.write_buffer_size),
          ToString(options_.write_buffer_size * 2),
          ToString(options_.write_buffer_size * 4)}},
        {"max_write_buffer_number",
         {ToString(options_.max_write_buffer_number),
          ToString(options_.max_write_buffer_number * 2),
          ToString(options_.max_write_buffer_number * 4)}},
        {"arena_block_size",
         {
             ToString(options_.arena_block_size),
             ToString(options_.write_buffer_size / 4),
             ToString(options_.write_buffer_size / 8),
         }},
        {"memtable_huge_page_size", {"0", ToString(2 * 1024 * 1024)}},
        {"max_successive_merges", {"0", "2", "4"}},
        {"inplace_update_num_locks", {"100", "200", "300"}},
        // TODO(ljin): enable test for this option
        // {"disable_auto_compactions", {"100", "200", "300"}},
        {"soft_rate_limit", {"0", "0.5", "0.9"}},
        {"hard_rate_limit", {"0", "1.1", "2.0"}},
        {"level0_file_num_compaction_trigger",
         {
             ToString(options_.level0_file_num_compaction_trigger),
             ToString(options_.level0_file_num_compaction_trigger + 2),
             ToString(options_.level0_file_num_compaction_trigger + 4),
         }},
        {"level0_slowdown_writes_trigger",
         {
             ToString(options_.level0_slowdown_writes_trigger),
             ToString(options_.level0_slowdown_writes_trigger + 2),
             ToString(options_.level0_slowdown_writes_trigger + 4),
         }},
        {"level0_stop_writes_trigger",
         {
             ToString(options_.level0_stop_writes_trigger),
             ToString(options_.level0_stop_writes_trigger + 2),
             ToString(options_.level0_stop_writes_trigger + 4),
         }},
        {"max_compaction_bytes",
         {
             ToString(options_.target_file_size_base * 5),
             ToString(options_.target_file_size_base * 15),
             ToString(options_.target_file_size_base * 100),
         }},
        {"target_file_size_base",
         {
             ToString(options_.target_file_size_base),
             ToString(options_.target_file_size_base * 2),
             ToString(options_.target_file_size_base * 4),
         }},
        {"target_file_size_multiplier",
         {
             ToString(options_.target_file_size_multiplier), "1", "2",
         }},
        {"max_bytes_for_level_base",
         {
             ToString(options_.max_bytes_for_level_base / 2),
             ToString(options_.max_bytes_for_level_base),
             ToString(options_.max_bytes_for_level_base * 2),
         }},
        {"max_bytes_for_level_multiplier",
         {
             ToString(options_.max_bytes_for_level_multiplier), "1", "2",
         }},
        {"max_sequential_skip_in_iterations", {"4", "8", "12"}},
        {"use_direct_reads", {"false", "true"}},
        {"use_direct_io_for_flush_and_compaction", {"false", "true"}},
    };

    options_table_ = std::move(options_tbl);

    for (const auto& iter : options_table_) {
      options_index_.push_back(iter.first);
    }
    return true;
  }

  bool Run() {
    PrintEnv();
    Open();
    BuildOptionsTable();
    SharedState shared(this);
    uint32_t n = shared.GetNumThreads();

    std::vector<ThreadState*> threads(n);
    for (uint32_t i = 0; i < n; i++) {
      threads[i] = new ThreadState(i, &shared);
      FLAGS_env->StartThread(ThreadBody, threads[i]);
    }
    ThreadState bg_thread(0, &shared);
    if (FLAGS_compaction_thread_pool_adjust_interval > 0) {
      FLAGS_env->StartThread(PoolSizeChangeThread, &bg_thread);
    }

    // Each thread goes through the following states:
    // initializing -> wait for others to init -> read/populate/depopulate
    // wait for others to operate -> verify -> done

    {
      MutexLock l(shared.GetMutex());
      while (!shared.AllInitialized()) {
        shared.GetCondVar()->Wait();
      }
      if (shared.ShouldVerifyAtBeginning()) {
        if (shared.HasVerificationFailedYet()) {
          printf("Crash-recovery verification failed :(\n");
        } else {
          printf("Crash-recovery verification passed :)\n");
        }
      }

      auto now = FLAGS_env->NowMicros();
      fprintf(stdout, "%s Starting database operations\n",
              FLAGS_env->TimeToString(now/1000000).c_str());

      shared.SetStart();
      shared.GetCondVar()->SignalAll();
      while (!shared.AllOperated()) {
        shared.GetCondVar()->Wait();
      }

      now = FLAGS_env->NowMicros();
      if (FLAGS_test_batches_snapshots) {
        fprintf(stdout, "%s Limited verification already done during gets\n",
                FLAGS_env->TimeToString((uint64_t) now/1000000).c_str());
      } else {
        fprintf(stdout, "%s Starting verification\n",
                FLAGS_env->TimeToString((uint64_t) now/1000000).c_str());
      }

      shared.SetStartVerify();
      shared.GetCondVar()->SignalAll();
      while (!shared.AllDone()) {
        shared.GetCondVar()->Wait();
      }
    }

    for (unsigned int i = 1; i < n; i++) {
      threads[0]->stats.Merge(threads[i]->stats);
    }
    threads[0]->stats.Report("Stress Test");

    for (unsigned int i = 0; i < n; i++) {
      delete threads[i];
      threads[i] = nullptr;
    }
    auto now = FLAGS_env->NowMicros();
    if (!FLAGS_test_batches_snapshots && !shared.HasVerificationFailedYet()) {
      fprintf(stdout, "%s Verification successful\n",
              FLAGS_env->TimeToString(now/1000000).c_str());
    }
    PrintStatistics();

    if (FLAGS_compaction_thread_pool_adjust_interval > 0) {
      MutexLock l(shared.GetMutex());
      shared.SetShouldStopBgThread();
      while (!shared.BgThreadFinished()) {
        shared.GetCondVar()->Wait();
      }
    }

    if (shared.HasVerificationFailedYet()) {
      printf("Verification failed :(\n");
      return false;
    }
    return true;
  }

 private:
  Status AssertSame(DB* db, ColumnFamilyHandle* cf,
                    ThreadState::SnapshotState& snap_state) {
    Status s;
    if (cf->GetName() != snap_state.cf_at_name) {
      return s;
    }
    ReadOptions ropt;
    ropt.snapshot = snap_state.snapshot;
    PinnableSlice exp_v(&snap_state.value);
    exp_v.PinSelf();
    PinnableSlice v;
    s = db->Get(ropt, cf, snap_state.key, &v);
    if (!s.ok() && !s.IsNotFound()) {
      return s;
    }
    if (snap_state.status != s) {
      return Status::Corruption(
          "The snapshot gave inconsistent results for key " +
          ToString(Hash(snap_state.key.c_str(), snap_state.key.size(), 0)) +
          " in cf " + cf->GetName() + ": (" + snap_state.status.ToString() +
          ") vs. (" + s.ToString() + ")");
    }
    if (s.ok()) {
      if (exp_v != v) {
        return Status::Corruption("The snapshot gave inconsistent values: (" +
                                  exp_v.ToString() + ") vs. (" + v.ToString() +
                                  ")");
      }
    }
    return Status::OK();
  }

  static void ThreadBody(void* v) {
    ThreadState* thread = reinterpret_cast<ThreadState*>(v);
    SharedState* shared = thread->shared;

    if (shared->ShouldVerifyAtBeginning()) {
      thread->shared->GetStressTest()->VerifyDb(thread);
    }
    {
      MutexLock l(shared->GetMutex());
      shared->IncInitialized();
      if (shared->AllInitialized()) {
        shared->GetCondVar()->SignalAll();
      }
      while (!shared->Started()) {
        shared->GetCondVar()->Wait();
      }
    }
    thread->shared->GetStressTest()->OperateDb(thread);

    {
      MutexLock l(shared->GetMutex());
      shared->IncOperated();
      if (shared->AllOperated()) {
        shared->GetCondVar()->SignalAll();
      }
      while (!shared->VerifyStarted()) {
        shared->GetCondVar()->Wait();
      }
    }

    if (!FLAGS_test_batches_snapshots) {
      thread->shared->GetStressTest()->VerifyDb(thread);
    }

    {
      MutexLock l(shared->GetMutex());
      shared->IncDone();
      if (shared->AllDone()) {
        shared->GetCondVar()->SignalAll();
      }
    }

  }

  static void PoolSizeChangeThread(void* v) {
    assert(FLAGS_compaction_thread_pool_adjust_interval > 0);
    ThreadState* thread = reinterpret_cast<ThreadState*>(v);
    SharedState* shared = thread->shared;

    while (true) {
      {
        MutexLock l(shared->GetMutex());
        if (shared->ShoudStopBgThread()) {
          shared->SetBgThreadFinish();
          shared->GetCondVar()->SignalAll();
          return;
        }
      }

      auto thread_pool_size_base = FLAGS_max_background_compactions;
      auto thread_pool_size_var = FLAGS_compaction_thread_pool_variations;
      int new_thread_pool_size =
          thread_pool_size_base - thread_pool_size_var +
          thread->rand.Next() % (thread_pool_size_var * 2 + 1);
      if (new_thread_pool_size < 1) {
        new_thread_pool_size = 1;
      }
      FLAGS_env->SetBackgroundThreads(new_thread_pool_size);
      // Sleep up to 3 seconds
      FLAGS_env->SleepForMicroseconds(
          thread->rand.Next() % FLAGS_compaction_thread_pool_adjust_interval *
              1000 +
          1);
    }
  }

  // Given a key K and value V, this puts ("0"+K, "0"+V), ("1"+K, "1"+V), ...
  // ("9"+K, "9"+V) in DB atomically i.e in a single batch.
  // Also refer MultiGet.
  Status MultiPut(ThreadState* thread, const WriteOptions& writeoptions,
                  ColumnFamilyHandle* column_family, const Slice& key,
                  const Slice& value, size_t sz) {
    std::string keys[10] = {"9", "8", "7", "6", "5",
                            "4", "3", "2", "1", "0"};
    std::string values[10] = {"9", "8", "7", "6", "5",
                              "4", "3", "2", "1", "0"};
    Slice value_slices[10];
    WriteBatch batch;
    Status s;
    for (int i = 0; i < 10; i++) {
      keys[i] += key.ToString();
      values[i] += value.ToString();
      value_slices[i] = values[i];
      if (FLAGS_use_merge) {
        batch.Merge(column_family, keys[i], value_slices[i]);
      } else {
        batch.Put(column_family, keys[i], value_slices[i]);
      }
    }

    s = db_->Write(writeoptions, &batch);
    if (!s.ok()) {
      fprintf(stderr, "multiput error: %s\n", s.ToString().c_str());
      thread->stats.AddErrors(1);
    } else {
      // we did 10 writes each of size sz + 1
      thread->stats.AddBytesForWrites(10, (sz + 1) * 10);
    }

    return s;
  }

  // Given a key K, this deletes ("0"+K), ("1"+K),... ("9"+K)
  // in DB atomically i.e in a single batch. Also refer MultiGet.
  Status MultiDelete(ThreadState* thread, const WriteOptions& writeoptions,
                     ColumnFamilyHandle* column_family, const Slice& key) {
    std::string keys[10] = {"9", "7", "5", "3", "1",
                            "8", "6", "4", "2", "0"};

    WriteBatch batch;
    Status s;
    for (int i = 0; i < 10; i++) {
      keys[i] += key.ToString();
      batch.Delete(column_family, keys[i]);
    }

    s = db_->Write(writeoptions, &batch);
    if (!s.ok()) {
      fprintf(stderr, "multidelete error: %s\n", s.ToString().c_str());
      thread->stats.AddErrors(1);
    } else {
      thread->stats.AddDeletes(10);
    }

    return s;
  }

  // Given a key K, this gets values for "0"+K, "1"+K,..."9"+K
  // in the same snapshot, and verifies that all the values are of the form
  // "0"+V, "1"+V,..."9"+V.
  // ASSUMES that MultiPut was used to put (K, V) into the DB.
  Status MultiGet(ThreadState* thread, const ReadOptions& readoptions,
                  ColumnFamilyHandle* column_family, const Slice& key,
                  std::string* value) {
    std::string keys[10] = {"0", "1", "2", "3", "4", "5", "6", "7", "8", "9"};
    Slice key_slices[10];
    std::string values[10];
    ReadOptions readoptionscopy = readoptions;
    readoptionscopy.snapshot = db_->GetSnapshot();
    Status s;
    for (int i = 0; i < 10; i++) {
      keys[i] += key.ToString();
      key_slices[i] = keys[i];
      s = db_->Get(readoptionscopy, column_family, key_slices[i], value);
      if (!s.ok() && !s.IsNotFound()) {
        fprintf(stderr, "get error: %s\n", s.ToString().c_str());
        values[i] = "";
        thread->stats.AddErrors(1);
        // we continue after error rather than exiting so that we can
        // find more errors if any
      } else if (s.IsNotFound()) {
        values[i] = "";
        thread->stats.AddGets(1, 0);
      } else {
        values[i] = *value;

        char expected_prefix = (keys[i])[0];
        char actual_prefix = (values[i])[0];
        if (actual_prefix != expected_prefix) {
          fprintf(stderr, "error expected prefix = %c actual = %c\n",
                  expected_prefix, actual_prefix);
        }
        (values[i])[0] = ' '; // blank out the differing character
        thread->stats.AddGets(1, 1);
      }
    }
    db_->ReleaseSnapshot(readoptionscopy.snapshot);

    // Now that we retrieved all values, check that they all match
    for (int i = 1; i < 10; i++) {
      if (values[i] != values[0]) {
        fprintf(stderr, "error : inconsistent values for key %s: %s, %s\n",
                key.ToString(true).c_str(), StringToHex(values[0]).c_str(),
                StringToHex(values[i]).c_str());
      // we continue after error rather than exiting so that we can
      // find more errors if any
      }
    }

    return s;
  }

  // Given a key, this does prefix scans for "0"+P, "1"+P,..."9"+P
  // in the same snapshot where P is the first FLAGS_prefix_size - 1 bytes
  // of the key. Each of these 10 scans returns a series of values;
  // each series should be the same length, and it is verified for each
  // index i that all the i'th values are of the form "0"+V, "1"+V,..."9"+V.
  // ASSUMES that MultiPut was used to put (K, V)
  Status MultiPrefixScan(ThreadState* thread, const ReadOptions& readoptions,
                         ColumnFamilyHandle* column_family,
                         const Slice& key) {
    std::string prefixes[10] = {"0", "1", "2", "3", "4",
                                "5", "6", "7", "8", "9"};
    Slice prefix_slices[10];
    ReadOptions readoptionscopy[10];
    const Snapshot* snapshot = db_->GetSnapshot();
    Iterator* iters[10];
    Status s = Status::OK();
    for (int i = 0; i < 10; i++) {
      prefixes[i] += key.ToString();
      prefixes[i].resize(FLAGS_prefix_size);
      prefix_slices[i] = Slice(prefixes[i]);
      readoptionscopy[i] = readoptions;
      readoptionscopy[i].snapshot = snapshot;
      iters[i] = db_->NewIterator(readoptionscopy[i], column_family);
      iters[i]->Seek(prefix_slices[i]);
    }

    int count = 0;
    while (iters[0]->Valid() && iters[0]->key().starts_with(prefix_slices[0])) {
      count++;
      std::string values[10];
      // get list of all values for this iteration
      for (int i = 0; i < 10; i++) {
        // no iterator should finish before the first one
        assert(iters[i]->Valid() &&
               iters[i]->key().starts_with(prefix_slices[i]));
        values[i] = iters[i]->value().ToString();

        char expected_first = (prefixes[i])[0];
        char actual_first = (values[i])[0];

        if (actual_first != expected_first) {
          fprintf(stderr, "error expected first = %c actual = %c\n",
                  expected_first, actual_first);
        }
        (values[i])[0] = ' '; // blank out the differing character
      }
      // make sure all values are equivalent
      for (int i = 0; i < 10; i++) {
        if (values[i] != values[0]) {
          fprintf(stderr, "error : %d, inconsistent values for prefix %s: %s, %s\n",
                  i, prefixes[i].c_str(), StringToHex(values[0]).c_str(),
                  StringToHex(values[i]).c_str());
          // we continue after error rather than exiting so that we can
          // find more errors if any
        }
        iters[i]->Next();
      }
    }

    // cleanup iterators and snapshot
    for (int i = 0; i < 10; i++) {
      // if the first iterator finished, they should have all finished
      assert(!iters[i]->Valid() ||
             !iters[i]->key().starts_with(prefix_slices[i]));
      assert(iters[i]->status().ok());
      delete iters[i];
    }
    db_->ReleaseSnapshot(snapshot);

    if (s.ok()) {
      thread->stats.AddPrefixes(1, count);
    } else {
      thread->stats.AddErrors(1);
    }

    return s;
  }

  // Given a key K, this creates an iterator which scans to K and then
  // does a random sequence of Next/Prev operations.
  Status MultiIterate(ThreadState* thread, const ReadOptions& readoptions,
                      ColumnFamilyHandle* column_family, const Slice& key) {
    Status s;
    const Snapshot* snapshot = db_->GetSnapshot();
    ReadOptions readoptionscopy = readoptions;
    readoptionscopy.snapshot = snapshot;
    unique_ptr<Iterator> iter(db_->NewIterator(readoptionscopy, column_family));

    iter->Seek(key);
    for (uint64_t i = 0; i < FLAGS_num_iterations && iter->Valid(); i++) {
      if (thread->rand.OneIn(2)) {
        iter->Next();
      } else {
        iter->Prev();
      }
    }

    if (s.ok()) {
      thread->stats.AddIterations(1);
    } else {
      thread->stats.AddErrors(1);
    }

    db_->ReleaseSnapshot(snapshot);

    return s;
  }

  Status SetOptions(ThreadState* thread) {
    assert(FLAGS_set_options_one_in > 0);
    std::unordered_map<std::string, std::string> opts;
    std::string name = options_index_[
      thread->rand.Next() % options_index_.size()];
    int value_idx = thread->rand.Next() % options_table_[name].size();
    if (name == "soft_rate_limit" || name == "hard_rate_limit") {
      opts["soft_rate_limit"] = options_table_["soft_rate_limit"][value_idx];
      opts["hard_rate_limit"] = options_table_["hard_rate_limit"][value_idx];
    } else if (name == "level0_file_num_compaction_trigger" ||
               name == "level0_slowdown_writes_trigger" ||
               name == "level0_stop_writes_trigger") {
      opts["level0_file_num_compaction_trigger"] =
        options_table_["level0_file_num_compaction_trigger"][value_idx];
      opts["level0_slowdown_writes_trigger"] =
        options_table_["level0_slowdown_writes_trigger"][value_idx];
      opts["level0_stop_writes_trigger"] =
        options_table_["level0_stop_writes_trigger"][value_idx];
    } else {
      opts[name] = options_table_[name][value_idx];
    }

    int rand_cf_idx = thread->rand.Next() % FLAGS_column_families;
    auto cfh = column_families_[rand_cf_idx];
    return db_->SetOptions(cfh, opts);
  }

#ifndef ROCKSDB_LITE
  Status NewTxn(WriteOptions& write_opts, Transaction** txn) {
    if (!FLAGS_use_txn) {
      return Status::InvalidArgument("NewTxn when FLAGS_use_txn is not set");
    }
    static std::atomic<uint64_t> txn_id = {0};
    TransactionOptions txn_options;
    *txn = txn_db_->BeginTransaction(write_opts, txn_options);
    auto istr = std::to_string(txn_id.fetch_add(1));
    Status s = (*txn)->SetName("xid" + istr);
    return s;
  }

  Status CommitTxn(Transaction* txn) {
    if (!FLAGS_use_txn) {
      return Status::InvalidArgument("CommitTxn when FLAGS_use_txn is not set");
    }
    Status s = txn->Prepare();
    if (s.ok()) {
      s = txn->Commit();
    }
    delete txn;
    return s;
  }
#endif

  void OperateDb(ThreadState* thread) {
    ReadOptions read_opts(FLAGS_verify_checksum, true);
    WriteOptions write_opts;
    auto shared = thread->shared;
    char value[100];
    auto max_key = thread->shared->GetMaxKey();
    std::string from_db;
    if (FLAGS_sync) {
      write_opts.sync = true;
    }
    write_opts.disableWAL = FLAGS_disable_wal;
    const int prefixBound = (int)FLAGS_readpercent + (int)FLAGS_prefixpercent;
    const int writeBound = prefixBound + (int)FLAGS_writepercent;
    const int delBound = writeBound + (int)FLAGS_delpercent;
    const int delRangeBound = delBound + (int)FLAGS_delrangepercent;

    thread->stats.Start();
    for (uint64_t i = 0; i < FLAGS_ops_per_thread; i++) {
      if (thread->shared->HasVerificationFailedYet()) {
        break;
      }
      if (i != 0 && (i % (FLAGS_ops_per_thread / (FLAGS_reopen + 1))) == 0) {
        {
          thread->stats.FinishedSingleOp();
          MutexLock l(thread->shared->GetMutex());
          while (!thread->snapshot_queue.empty()) {
            db_->ReleaseSnapshot(
                thread->snapshot_queue.front().second.snapshot);
            thread->snapshot_queue.pop();
          }
          thread->shared->IncVotedReopen();
          if (thread->shared->AllVotedReopen()) {
            thread->shared->GetStressTest()->Reopen();
            thread->shared->GetCondVar()->SignalAll();
          }
          else {
            thread->shared->GetCondVar()->Wait();
          }
          // Commenting this out as we don't want to reset stats on each open.
          // thread->stats.Start();
        }
      }

      // Change Options
      if (FLAGS_set_options_one_in > 0 &&
          thread->rand.OneIn(FLAGS_set_options_one_in)) {
        SetOptions(thread);
      }

      if (FLAGS_set_in_place_one_in > 0 &&
          thread->rand.OneIn(FLAGS_set_in_place_one_in)) {
        options_.inplace_update_support ^= options_.inplace_update_support;
      }

      if (!FLAGS_test_batches_snapshots &&
          FLAGS_clear_column_family_one_in != 0 && FLAGS_column_families > 1) {
        if (thread->rand.OneIn(FLAGS_clear_column_family_one_in)) {
          // drop column family and then create it again (can't drop default)
          int cf = thread->rand.Next() % (FLAGS_column_families - 1) + 1;
          std::string new_name =
              ToString(new_column_family_name_.fetch_add(1));
          {
            MutexLock l(thread->shared->GetMutex());
            fprintf(
                stdout,
                "[CF %d] Dropping and recreating column family. new name: %s\n",
                cf, new_name.c_str());
          }
          thread->shared->LockColumnFamily(cf);
          Status s __attribute__((__unused__));
          s = db_->DropColumnFamily(column_families_[cf]);
          delete column_families_[cf];
          if (!s.ok()) {
            fprintf(stderr, "dropping column family error: %s\n",
                s.ToString().c_str());
            std::terminate();
          }
          s = db_->CreateColumnFamily(ColumnFamilyOptions(options_), new_name,
                                      &column_families_[cf]);
          column_family_names_[cf] = new_name;
          thread->shared->ClearColumnFamily(cf);
          if (!s.ok()) {
            fprintf(stderr, "creating column family error: %s\n",
                s.ToString().c_str());
            std::terminate();
          }
          thread->shared->UnlockColumnFamily(cf);
        }
      }

#ifndef ROCKSDB_LITE  // Lite does not support GetColumnFamilyMetaData
      if (FLAGS_compact_files_one_in > 0 &&
          thread->rand.Uniform(FLAGS_compact_files_one_in) == 0) {
        auto* random_cf =
            column_families_[thread->rand.Next() % FLAGS_column_families];
        rocksdb::ColumnFamilyMetaData cf_meta_data;
        db_->GetColumnFamilyMetaData(random_cf, &cf_meta_data);

        // Randomly compact up to three consecutive files from a level
        const int kMaxRetry = 3;
        for (int attempt = 0; attempt < kMaxRetry; ++attempt) {
          size_t random_level = thread->rand.Uniform(
              static_cast<int>(cf_meta_data.levels.size()));

          const auto& files = cf_meta_data.levels[random_level].files;
          if (files.size() > 0) {
            size_t random_file_index =
                thread->rand.Uniform(static_cast<int>(files.size()));
            if (files[random_file_index].being_compacted) {
              // Retry as the selected file is currently being compacted
              continue;
            }

            std::vector<std::string> input_files;
            input_files.push_back(files[random_file_index].name);
            if (random_file_index > 0 &&
                !files[random_file_index - 1].being_compacted) {
              input_files.push_back(files[random_file_index - 1].name);
            }
            if (random_file_index + 1 < files.size() &&
                !files[random_file_index + 1].being_compacted) {
              input_files.push_back(files[random_file_index + 1].name);
            }

            size_t output_level =
                std::min(random_level + 1, cf_meta_data.levels.size() - 1);
            auto s =
                db_->CompactFiles(CompactionOptions(), random_cf, input_files,
                                  static_cast<int>(output_level));
            if (!s.ok()) {
              printf("Unable to perform CompactFiles(): %s\n",
                     s.ToString().c_str());
              thread->stats.AddNumCompactFilesFailed(1);
            } else {
              thread->stats.AddNumCompactFilesSucceed(1);
            }
            break;
          }
        }
      }
#endif                // !ROCKSDB_LITE
      const double completed_ratio =
          static_cast<double>(i) / FLAGS_ops_per_thread;
      const int64_t base_key = static_cast<int64_t>(
          completed_ratio * (FLAGS_max_key - FLAGS_active_width));
      int64_t rand_key = base_key + thread->rand.Next() % FLAGS_active_width;
      int rand_column_family = thread->rand.Next() % FLAGS_column_families;
      std::string keystr = Key(rand_key);
      Slice key = keystr;
      std::unique_ptr<MutexLock> l;
      if (!FLAGS_test_batches_snapshots) {
        l.reset(new MutexLock(
            shared->GetMutexForKey(rand_column_family, rand_key)));
      }

      auto column_family = column_families_[rand_column_family];

      if (FLAGS_acquire_snapshot_one_in > 0 &&
          thread->rand.Uniform(FLAGS_acquire_snapshot_one_in) == 0) {
        auto snapshot = db_->GetSnapshot();
        ReadOptions ropt;
        ropt.snapshot = snapshot;
        std::string value_at;
        // When taking a snapshot, we also read a key from that snapshot. We
        // will later read the same key before releasing the snapshot and verify
        // that the results are the same.
        auto status_at = db_->Get(ropt, column_family, key, &value_at);
        ThreadState::SnapshotState snap_state = {
            snapshot, rand_column_family, column_family->GetName(),
            keystr,   status_at,          value_at};
        thread->snapshot_queue.emplace(
            std::min(FLAGS_ops_per_thread - 1, i + FLAGS_snapshot_hold_ops),
            snap_state);
      }
      while (!thread->snapshot_queue.empty() &&
             i == thread->snapshot_queue.front().first) {
        auto snap_state = thread->snapshot_queue.front().second;
        assert(snap_state.snapshot);
        // Note: this is unsafe as the cf might be dropped concurrently. But it
        // is ok since unclean cf drop is cunnrently not supported by write
        // prepared transactions.
        Status s =
            AssertSame(db_, column_families_[snap_state.cf_at], snap_state);
        if (!s.ok()) {
          VerificationAbort(shared, "Snapshot gave inconsistent state", s);
        }
        db_->ReleaseSnapshot(snap_state.snapshot);
        thread->snapshot_queue.pop();
      }

      int prob_op = thread->rand.Uniform(100);
      if (prob_op >= 0 && prob_op < (int)FLAGS_readpercent) {
        // OPERATION read
        if (!FLAGS_test_batches_snapshots) {
          Status s = db_->Get(read_opts, column_family, key, &from_db);
          if (s.ok()) {
            // found case
            thread->stats.AddGets(1, 1);
          } else if (s.IsNotFound()) {
            // not found case
            thread->stats.AddGets(1, 0);
          } else {
            // errors case
            thread->stats.AddErrors(1);
          }
        } else {
          MultiGet(thread, read_opts, column_family, key, &from_db);
        }
      } else if ((int)FLAGS_readpercent <= prob_op && prob_op < prefixBound) {
        // OPERATION prefix scan
        // keys are 8 bytes long, prefix size is FLAGS_prefix_size. There are
        // (8 - FLAGS_prefix_size) bytes besides the prefix. So there will
        // be 2 ^ ((8 - FLAGS_prefix_size) * 8) possible keys with the same
        // prefix
        if (!FLAGS_test_batches_snapshots) {
          Slice prefix = Slice(key.data(), FLAGS_prefix_size);
          Iterator* iter = db_->NewIterator(read_opts, column_family);
          int64_t count = 0;
          for (iter->Seek(prefix);
               iter->Valid() && iter->key().starts_with(prefix); iter->Next()) {
            ++count;
          }
          assert(count <=
                 (static_cast<int64_t>(1) << ((8 - FLAGS_prefix_size) * 8)));
          if (iter->status().ok()) {
            thread->stats.AddPrefixes(1, static_cast<int>(count));
          } else {
            thread->stats.AddErrors(1);
          }
          delete iter;
        } else {
          MultiPrefixScan(thread, read_opts, column_family, key);
        }
      } else if (prefixBound <= prob_op && prob_op < writeBound) {
        // OPERATION write
        uint32_t value_base = thread->rand.Next() % shared->UNKNOWN_SENTINEL;
        size_t sz = GenerateValue(value_base, value, sizeof(value));
        Slice v(value, sz);
        if (!FLAGS_test_batches_snapshots) {
          // If the chosen key does not allow overwrite and it already
          // exists, choose another key. Also avoid using merge operands in
          // no-overwrite positions (where single delete will be called later),
          // as those features have undefined behavior when used together.
          while (!shared->AllowsOverwrite(rand_column_family, rand_key) &&
                 (FLAGS_use_merge ||
                  shared->Exists(rand_column_family, rand_key))) {
            l.reset();
            rand_key = thread->rand.Next() % max_key;
            rand_column_family = thread->rand.Next() % FLAGS_column_families;
            l.reset(new MutexLock(
                shared->GetMutexForKey(rand_column_family, rand_key)));
          }

          keystr = Key(rand_key);
          key = keystr;
          column_family = column_families_[rand_column_family];

          if (FLAGS_verify_before_write) {
            std::string keystr2 = Key(rand_key);
            Slice k = keystr2;
            Status s = db_->Get(read_opts, column_family, k, &from_db);
            if (!VerifyValue(rand_column_family, rand_key, read_opts,
                             thread->shared, from_db, s, true)) {
              break;
            }
          }
          shared->Put(rand_column_family, rand_key, value_base,
                      true /* pending */);
          Status s;
          if (FLAGS_use_merge) {
            if (!FLAGS_use_txn) {
              s = db_->Merge(write_opts, column_family, key, v);
            } else {
#ifndef ROCKSDB_LITE
              Transaction* txn;
              s = NewTxn(write_opts, &txn);
              if (s.ok()) {
                s = txn->Merge(column_family, key, v);
                if (s.ok()) {
                  s = CommitTxn(txn);
                }
              }
#endif
            }
          } else {
            if (!FLAGS_use_txn) {
              s = db_->Put(write_opts, column_family, key, v);
            } else {
#ifndef ROCKSDB_LITE
              Transaction* txn;
              s = NewTxn(write_opts, &txn);
              if (s.ok()) {
                s = txn->Put(column_family, key, v);
                if (s.ok()) {
                  s = CommitTxn(txn);
                }
              }
#endif
            }
          }
          shared->Put(rand_column_family, rand_key, value_base,
                      false /* pending */);
          if (!s.ok()) {
            fprintf(stderr, "put or merge error: %s\n", s.ToString().c_str());
            std::terminate();
          }
          thread->stats.AddBytesForWrites(1, sz);
        } else {
          MultiPut(thread, write_opts, column_family, key, v, sz);
        }
        PrintKeyValue(rand_column_family, static_cast<uint32_t>(rand_key),
                      value, sz);
      } else if (writeBound <= prob_op && prob_op < delBound) {
        // OPERATION delete
        if (!FLAGS_test_batches_snapshots) {
          // If the chosen key does not allow overwrite and it does not exist,
          // choose another key.
          while (!shared->AllowsOverwrite(rand_column_family, rand_key) &&
                 !shared->Exists(rand_column_family, rand_key)) {
            l.reset();
            rand_key = thread->rand.Next() % max_key;
            rand_column_family = thread->rand.Next() % FLAGS_column_families;
            l.reset(new MutexLock(
                shared->GetMutexForKey(rand_column_family, rand_key)));
          }

          keystr = Key(rand_key);
          key = keystr;
          column_family = column_families_[rand_column_family];

          // Use delete if the key may be overwritten and a single deletion
          // otherwise.
          if (shared->AllowsOverwrite(rand_column_family, rand_key)) {
            shared->Delete(rand_column_family, rand_key, true /* pending */);
            Status s;
            if (!FLAGS_use_txn) {
              s = db_->Delete(write_opts, column_family, key);
            } else {
#ifndef ROCKSDB_LITE
              Transaction* txn;
              s = NewTxn(write_opts, &txn);
              if (s.ok()) {
                s = txn->Delete(column_family, key);
                if (s.ok()) {
                  s = CommitTxn(txn);
                }
              }
#endif
            }
            shared->Delete(rand_column_family, rand_key, false /* pending */);
            thread->stats.AddDeletes(1);
            if (!s.ok()) {
              fprintf(stderr, "delete error: %s\n", s.ToString().c_str());
              std::terminate();
            }
          } else {
            shared->SingleDelete(rand_column_family, rand_key,
                                 true /* pending */);
            Status s;
            if (!FLAGS_use_txn) {
              s = db_->SingleDelete(write_opts, column_family, key);
            } else {
#ifndef ROCKSDB_LITE
              Transaction* txn;
              s = NewTxn(write_opts, &txn);
              if (s.ok()) {
                s = txn->SingleDelete(column_family, key);
                if (s.ok()) {
                  s = CommitTxn(txn);
                }
              }
#endif
            }
            shared->SingleDelete(rand_column_family, rand_key,
                                 false /* pending */);
            thread->stats.AddSingleDeletes(1);
            if (!s.ok()) {
              fprintf(stderr, "single delete error: %s\n",
                      s.ToString().c_str());
              std::terminate();
            }
          }
        } else {
          MultiDelete(thread, write_opts, column_family, key);
        }
      } else if (delBound <= prob_op && prob_op < delRangeBound) {
        // OPERATION delete range
        if (!FLAGS_test_batches_snapshots) {
          std::vector<std::unique_ptr<MutexLock>> range_locks;
          // delete range does not respect disallowed overwrites. the keys for
          // which overwrites are disallowed are randomly distributed so it
          // could be expensive to find a range where each key allows
          // overwrites.
          if (rand_key > max_key - FLAGS_range_deletion_width) {
            l.reset();
            rand_key = thread->rand.Next() %
                       (max_key - FLAGS_range_deletion_width + 1);
            range_locks.emplace_back(new MutexLock(
                shared->GetMutexForKey(rand_column_family, rand_key)));
          } else {
            range_locks.emplace_back(std::move(l));
          }
          for (int j = 1; j < FLAGS_range_deletion_width; ++j) {
            if (((rand_key + j) & ((1 << FLAGS_log2_keys_per_lock) - 1)) == 0) {
              range_locks.emplace_back(new MutexLock(
                    shared->GetMutexForKey(rand_column_family, rand_key + j)));
            }
          }
          shared->DeleteRange(rand_column_family, rand_key,
                              rand_key + FLAGS_range_deletion_width,
                              true /* pending */);

          keystr = Key(rand_key);
          key = keystr;
          column_family = column_families_[rand_column_family];
          std::string end_keystr = Key(rand_key + FLAGS_range_deletion_width);
          Slice end_key = end_keystr;
          Status s = db_->DeleteRange(write_opts, column_family, key, end_key);
          if (!s.ok()) {
            fprintf(stderr, "delete range error: %s\n",
                    s.ToString().c_str());
            std::terminate();
          }
          int covered = shared->DeleteRange(
              rand_column_family, rand_key,
              rand_key + FLAGS_range_deletion_width, false /* pending */);
          thread->stats.AddRangeDeletions(1);
          thread->stats.AddCoveredByRangeDeletions(covered);
        }
      } else {
        // OPERATION iterate
        MultiIterate(thread, read_opts, column_family, key);
      }
      thread->stats.FinishedSingleOp();
    }

    thread->stats.Stop();
  }

  void VerifyDb(ThreadState* thread) const {
    ReadOptions options(FLAGS_verify_checksum, true);
    auto shared = thread->shared;
    const int64_t max_key = shared->GetMaxKey();
    const int64_t keys_per_thread = max_key / shared->GetNumThreads();
    int64_t start = keys_per_thread * thread->tid;
    int64_t end = start + keys_per_thread;
    if (thread->tid == shared->GetNumThreads() - 1) {
      end = max_key;
    }
    for (size_t cf = 0; cf < column_families_.size(); ++cf) {
      if (thread->shared->HasVerificationFailedYet()) {
        break;
      }
      if (!thread->rand.OneIn(2)) {
        // Use iterator to verify this range
        unique_ptr<Iterator> iter(
            db_->NewIterator(options, column_families_[cf]));
        iter->Seek(Key(start));
        for (auto i = start; i < end; i++) {
          if (thread->shared->HasVerificationFailedYet()) {
            break;
          }
          // TODO(ljin): update "long" to uint64_t
          // Reseek when the prefix changes
          if (i % (static_cast<int64_t>(1) << 8 * (8 - FLAGS_prefix_size)) ==
              0) {
            iter->Seek(Key(i));
          }
          std::string from_db;
          std::string keystr = Key(i);
          Slice k = keystr;
          Status s = iter->status();
          if (iter->Valid()) {
            if (iter->key().compare(k) > 0) {
              s = Status::NotFound(Slice());
            } else if (iter->key().compare(k) == 0) {
              from_db = iter->value().ToString();
              iter->Next();
            } else if (iter->key().compare(k) < 0) {
              VerificationAbort(shared, "An out of range key was found",
                                static_cast<int>(cf), i);
            }
          } else {
            // The iterator found no value for the key in question, so do not
            // move to the next item in the iterator
            s = Status::NotFound(Slice());
          }
          VerifyValue(static_cast<int>(cf), i, options, shared, from_db, s,
                      true);
          if (from_db.length()) {
            PrintKeyValue(static_cast<int>(cf), static_cast<uint32_t>(i),
                          from_db.data(), from_db.length());
          }
        }
      } else {
        // Use Get to verify this range
        for (auto i = start; i < end; i++) {
          if (thread->shared->HasVerificationFailedYet()) {
            break;
          }
          std::string from_db;
          std::string keystr = Key(i);
          Slice k = keystr;
          Status s = db_->Get(options, column_families_[cf], k, &from_db);
          VerifyValue(static_cast<int>(cf), i, options, shared, from_db, s,
                      true);
          if (from_db.length()) {
            PrintKeyValue(static_cast<int>(cf), static_cast<uint32_t>(i),
                          from_db.data(), from_db.length());
          }
        }
      }
    }
  }

  void VerificationAbort(SharedState* shared, std::string msg, Status s) const {
    printf("Verification failed: %s. Status is %s\n", msg.c_str(),
           s.ToString().c_str());
    shared->SetVerificationFailure();
  }

  void VerificationAbort(SharedState* shared, std::string msg, int cf,
                         int64_t key) const {
    printf("Verification failed for column family %d key %" PRIi64 ": %s\n", cf, key,
           msg.c_str());
    shared->SetVerificationFailure();
  }

  bool VerifyValue(int cf, int64_t key, const ReadOptions& /*opts*/,
                   SharedState* shared, const std::string& value_from_db,
                   Status s, bool strict = false) const {
    if (shared->HasVerificationFailedYet()) {
      return false;
    }
    // compare value_from_db with the value in the shared state
    char value[kValueMaxLen];
    uint32_t value_base = shared->Get(cf, key);
    if (value_base == SharedState::UNKNOWN_SENTINEL) {
      return true;
    }
    if (value_base == SharedState::DELETION_SENTINEL && !strict) {
      return true;
    }

    if (s.ok()) {
      if (value_base == SharedState::DELETION_SENTINEL) {
        VerificationAbort(shared, "Unexpected value found", cf, key);
        return false;
      }
      size_t sz = GenerateValue(value_base, value, sizeof(value));
      if (value_from_db.length() != sz) {
        VerificationAbort(shared, "Length of value read is not equal", cf, key);
        return false;
      }
      if (memcmp(value_from_db.data(), value, sz) != 0) {
        VerificationAbort(shared, "Contents of value read don't match", cf,
                          key);
        return false;
      }
    } else {
      if (value_base != SharedState::DELETION_SENTINEL) {
        VerificationAbort(shared, "Value not found: " + s.ToString(), cf, key);
        return false;
      }
    }
    return true;
  }

  static void PrintKeyValue(int cf, int64_t key, const char* value,
                            size_t sz) {
    if (!FLAGS_verbose) {
      return;
    }
    fprintf(stdout, "[CF %d] %" PRIi64 " == > (%" ROCKSDB_PRIszt ") ", cf, key, sz);
    for (size_t i = 0; i < sz; i++) {
      fprintf(stdout, "%X", value[i]);
    }
    fprintf(stdout, "\n");
  }

  static size_t GenerateValue(uint32_t rand, char *v, size_t max_sz) {
    size_t value_sz =
        ((rand % kRandomValueMaxFactor) + 1) * FLAGS_value_size_mult;
    assert(value_sz <= max_sz && value_sz >= sizeof(uint32_t));
    (void) max_sz;
    *((uint32_t*)v) = rand;
    for (size_t i=sizeof(uint32_t); i < value_sz; i++) {
      v[i] = (char)(rand ^ i);
    }
    v[value_sz] = '\0';
    return value_sz; // the size of the value set.
  }

  void PrintEnv() const {
    fprintf(stdout, "RocksDB version           : %d.%d\n", kMajorVersion,
            kMinorVersion);
    fprintf(stdout, "TransactionDB             : %s\n",
            FLAGS_use_txn ? "true" : "false");
    fprintf(stdout, "Column families           : %d\n", FLAGS_column_families);
    if (!FLAGS_test_batches_snapshots) {
      fprintf(stdout, "Clear CFs one in          : %d\n",
              FLAGS_clear_column_family_one_in);
    }
    fprintf(stdout, "Number of threads         : %d\n", FLAGS_threads);
    fprintf(stdout, "Ops per thread            : %lu\n",
            (unsigned long)FLAGS_ops_per_thread);
    std::string ttl_state("unused");
    if (FLAGS_ttl > 0) {
      ttl_state = NumberToString(FLAGS_ttl);
    }
    fprintf(stdout, "Time to live(sec)         : %s\n", ttl_state.c_str());
    fprintf(stdout, "Read percentage           : %d%%\n", FLAGS_readpercent);
    fprintf(stdout, "Prefix percentage         : %d%%\n", FLAGS_prefixpercent);
    fprintf(stdout, "Write percentage          : %d%%\n", FLAGS_writepercent);
    fprintf(stdout, "Delete percentage         : %d%%\n", FLAGS_delpercent);
    fprintf(stdout, "Delete range percentage   : %d%%\n", FLAGS_delrangepercent);
    fprintf(stdout, "No overwrite percentage   : %d%%\n",
            FLAGS_nooverwritepercent);
    fprintf(stdout, "Iterate percentage        : %d%%\n", FLAGS_iterpercent);
    fprintf(stdout, "DB-write-buffer-size      : %" PRIu64 "\n",
            FLAGS_db_write_buffer_size);
    fprintf(stdout, "Write-buffer-size         : %d\n",
            FLAGS_write_buffer_size);
    fprintf(stdout, "Iterations                : %lu\n",
            (unsigned long)FLAGS_num_iterations);
    fprintf(stdout, "Max key                   : %lu\n",
            (unsigned long)FLAGS_max_key);
    fprintf(stdout, "Ratio #ops/#keys          : %f\n",
            (1.0 * FLAGS_ops_per_thread * FLAGS_threads) / FLAGS_max_key);
    fprintf(stdout, "Num times DB reopens      : %d\n", FLAGS_reopen);
    fprintf(stdout, "Batches/snapshots         : %d\n",
            FLAGS_test_batches_snapshots);
    fprintf(stdout, "Do update in place        : %d\n", FLAGS_in_place_update);
    fprintf(stdout, "Num keys per lock         : %d\n",
            1 << FLAGS_log2_keys_per_lock);
    std::string compression = CompressionTypeToString(FLAGS_compression_type_e);
    fprintf(stdout, "Compression               : %s\n", compression.c_str());
    std::string checksum = ChecksumTypeToString(FLAGS_checksum_type_e);
    fprintf(stdout, "Checksum type             : %s\n", checksum.c_str());
    fprintf(stdout, "Max subcompactions        : %" PRIu64 "\n",
            FLAGS_subcompactions);

    const char* memtablerep = "";
    switch (FLAGS_rep_factory) {
      case kSkipList:
        memtablerep = "skip_list";
        break;
      case kHashSkipList:
        memtablerep = "prefix_hash";
        break;
      case kVectorRep:
        memtablerep = "vector";
        break;
    }

    fprintf(stdout, "Memtablerep               : %s\n", memtablerep);

    fprintf(stdout, "Test kill odd             : %d\n", rocksdb_kill_odds);
    if (!rocksdb_kill_prefix_blacklist.empty()) {
      fprintf(stdout, "Skipping kill points prefixes:\n");
      for (auto& p : rocksdb_kill_prefix_blacklist) {
        fprintf(stdout, "  %s\n", p.c_str());
      }
    }

    fprintf(stdout, "------------------------------------------------\n");
  }

  void Open() {
    assert(db_ == nullptr);
#ifndef ROCKSDB_LITE
    assert(txn_db_ == nullptr);
#endif
    if (FLAGS_options_file.empty()) {
      BlockBasedTableOptions block_based_options;
      block_based_options.block_cache = cache_;
      block_based_options.block_cache_compressed = compressed_cache_;
      block_based_options.checksum = FLAGS_checksum_type_e;
      block_based_options.block_size = FLAGS_block_size;
      block_based_options.format_version = 2;
      block_based_options.filter_policy = filter_policy_;
      options_.table_factory.reset(
          NewBlockBasedTableFactory(block_based_options));
      options_.db_write_buffer_size = FLAGS_db_write_buffer_size;
      options_.write_buffer_size = FLAGS_write_buffer_size;
      options_.max_write_buffer_number = FLAGS_max_write_buffer_number;
      options_.min_write_buffer_number_to_merge =
          FLAGS_min_write_buffer_number_to_merge;
      options_.max_write_buffer_number_to_maintain =
          FLAGS_max_write_buffer_number_to_maintain;
      options_.memtable_prefix_bloom_size_ratio =
          FLAGS_memtable_prefix_bloom_size_ratio;
      options_.max_background_compactions = FLAGS_max_background_compactions;
      options_.max_background_flushes = FLAGS_max_background_flushes;
      options_.compaction_style =
          static_cast<rocksdb::CompactionStyle>(FLAGS_compaction_style);
      options_.prefix_extractor.reset(
          NewFixedPrefixTransform(FLAGS_prefix_size));
      options_.max_open_files = FLAGS_open_files;
      options_.statistics = dbstats;
      options_.env = FLAGS_env;
      options_.use_fsync = FLAGS_use_fsync;
      options_.compaction_readahead_size = FLAGS_compaction_readahead_size;
      options_.allow_mmap_reads = FLAGS_mmap_read;
      options_.allow_mmap_writes = FLAGS_mmap_write;
      options_.use_direct_reads = FLAGS_use_direct_reads;
      options_.use_direct_io_for_flush_and_compaction =
          FLAGS_use_direct_io_for_flush_and_compaction;
      options_.target_file_size_base = FLAGS_target_file_size_base;
      options_.target_file_size_multiplier = FLAGS_target_file_size_multiplier;
      options_.max_bytes_for_level_base = FLAGS_max_bytes_for_level_base;
      options_.max_bytes_for_level_multiplier =
          FLAGS_max_bytes_for_level_multiplier;
      options_.level0_stop_writes_trigger = FLAGS_level0_stop_writes_trigger;
      options_.level0_slowdown_writes_trigger =
          FLAGS_level0_slowdown_writes_trigger;
      options_.level0_file_num_compaction_trigger =
          FLAGS_level0_file_num_compaction_trigger;
      options_.compression = FLAGS_compression_type_e;
      options_.create_if_missing = true;
      options_.max_manifest_file_size = FLAGS_max_manifest_file_size;
      options_.inplace_update_support = FLAGS_in_place_update;
      options_.max_subcompactions = static_cast<uint32_t>(FLAGS_subcompactions);
      options_.allow_concurrent_memtable_write =
          FLAGS_allow_concurrent_memtable_write;
      options_.enable_write_thread_adaptive_yield =
          FLAGS_enable_write_thread_adaptive_yield;
      options_.compaction_options_universal.size_ratio =
          FLAGS_universal_size_ratio;
      options_.compaction_options_universal.min_merge_width =
          FLAGS_universal_min_merge_width;
      options_.compaction_options_universal.max_merge_width =
          FLAGS_universal_max_merge_width;
      options_.compaction_options_universal.max_size_amplification_percent =
          FLAGS_universal_max_size_amplification_percent;
    } else {
#ifdef ROCKSDB_LITE
      fprintf(stderr, "--options_file not supported in lite mode\n");
      exit(1);
#else
      DBOptions db_options;
      std::vector<ColumnFamilyDescriptor> cf_descriptors;
      Status s = LoadOptionsFromFile(FLAGS_options_file, Env::Default(),
                                     &db_options, &cf_descriptors);
      if (!s.ok()) {
        fprintf(stderr, "Unable to load options file %s --- %s\n",
                FLAGS_options_file.c_str(), s.ToString().c_str());
        exit(1);
      }
      options_ = Options(db_options, cf_descriptors[0].options);
#endif  // ROCKSDB_LITE
    }

    if (FLAGS_rate_limiter_bytes_per_sec > 0) {
      options_.rate_limiter.reset(NewGenericRateLimiter(
          FLAGS_rate_limiter_bytes_per_sec, 1000 /* refill_period_us */,
          10 /* fairness */,
          FLAGS_rate_limit_bg_reads ? RateLimiter::Mode::kReadsOnly
                                    : RateLimiter::Mode::kWritesOnly));
      if (FLAGS_rate_limit_bg_reads) {
        options_.new_table_reader_for_compaction_inputs = true;
      }
    }

    if (FLAGS_prefix_size == 0 && FLAGS_rep_factory == kHashSkipList) {
      fprintf(stderr,
              "prefeix_size cannot be zero if memtablerep == prefix_hash\n");
      exit(1);
    }
    if (FLAGS_prefix_size != 0 && FLAGS_rep_factory != kHashSkipList) {
      fprintf(stderr,
              "WARNING: prefix_size is non-zero but "
              "memtablerep != prefix_hash\n");
    }
    switch (FLAGS_rep_factory) {
      case kSkipList:
        // no need to do anything
        break;
#ifndef ROCKSDB_LITE
      case kHashSkipList:
        options_.memtable_factory.reset(NewHashSkipListRepFactory(10000));
        break;
      case kVectorRep:
        options_.memtable_factory.reset(new VectorRepFactory());
        break;
#else
      default:
        fprintf(stderr,
                "RocksdbLite only supports skip list mem table. Skip "
                "--rep_factory\n");
#endif  // ROCKSDB_LITE
    }

    if (FLAGS_use_full_merge_v1) {
      options_.merge_operator = MergeOperators::CreateDeprecatedPutOperator();
    } else {
      options_.merge_operator = MergeOperators::CreatePutOperator();
    }

    fprintf(stdout, "DB path: [%s]\n", FLAGS_db.c_str());

    Status s;
    if (FLAGS_ttl == -1) {
      std::vector<std::string> existing_column_families;
      s = DB::ListColumnFamilies(DBOptions(options_), FLAGS_db,
                                 &existing_column_families);  // ignore errors
      if (!s.ok()) {
        // DB doesn't exist
        assert(existing_column_families.empty());
        assert(column_family_names_.empty());
        column_family_names_.push_back(kDefaultColumnFamilyName);
      } else if (column_family_names_.empty()) {
        // this is the first call to the function Open()
        column_family_names_ = existing_column_families;
      } else {
        // this is a reopen. just assert that existing column_family_names are
        // equivalent to what we remember
        auto sorted_cfn = column_family_names_;
        std::sort(sorted_cfn.begin(), sorted_cfn.end());
        std::sort(existing_column_families.begin(),
                  existing_column_families.end());
        if (sorted_cfn != existing_column_families) {
          fprintf(stderr,
                  "Expected column families differ from the existing:\n");
          printf("Expected: {");
          for (auto cf : sorted_cfn) {
            printf("%s ", cf.c_str());
          }
          printf("}\n");
          printf("Existing: {");
          for (auto cf : existing_column_families) {
            printf("%s ", cf.c_str());
          }
          printf("}\n");
        }
        assert(sorted_cfn == existing_column_families);
      }
      std::vector<ColumnFamilyDescriptor> cf_descriptors;
      for (auto name : column_family_names_) {
        if (name != kDefaultColumnFamilyName) {
          new_column_family_name_ =
              std::max(new_column_family_name_.load(), std::stoi(name) + 1);
        }
        cf_descriptors.emplace_back(name, ColumnFamilyOptions(options_));
      }
      while (cf_descriptors.size() < (size_t)FLAGS_column_families) {
        std::string name = ToString(new_column_family_name_.load());
        new_column_family_name_++;
        cf_descriptors.emplace_back(name, ColumnFamilyOptions(options_));
        column_family_names_.push_back(name);
      }
      options_.listeners.clear();
      options_.listeners.emplace_back(
          new DbStressListener(FLAGS_db, options_.db_paths, cf_descriptors));
      options_.create_missing_column_families = true;
      if (!FLAGS_use_txn) {
        s = DB::Open(DBOptions(options_), FLAGS_db, cf_descriptors,
                     &column_families_, &db_);
      } else {
#ifndef ROCKSDB_LITE
        TransactionDBOptions txn_db_options;
        // For the moment it is sufficient to test WRITE_PREPARED policy
        txn_db_options.write_policy = TxnDBWritePolicy::WRITE_PREPARED;
        s = TransactionDB::Open(options_, txn_db_options, FLAGS_db,
                                cf_descriptors, &column_families_, &txn_db_);
        db_ = txn_db_;
        // after a crash, rollback to commit recovered transactions
        std::vector<Transaction*> trans;
        txn_db_->GetAllPreparedTransactions(&trans);
        Random rand(static_cast<uint32_t>(FLAGS_seed));
        for (auto txn : trans) {
          if (rand.OneIn(2)) {
            s = txn->Commit();
            assert(s.ok());
          } else {
            s = txn->Rollback();
            assert(s.ok());
          }
          delete txn;
        }
        trans.clear();
        txn_db_->GetAllPreparedTransactions(&trans);
        assert(trans.size() == 0);
#endif
      }
      assert(!s.ok() || column_families_.size() ==
                            static_cast<size_t>(FLAGS_column_families));
    } else {
#ifndef ROCKSDB_LITE
      DBWithTTL* db_with_ttl;
      s = DBWithTTL::Open(options_, FLAGS_db, &db_with_ttl, FLAGS_ttl);
      db_ = db_with_ttl;
#else
      fprintf(stderr, "TTL is not supported in RocksDBLite\n");
      exit(1);
#endif
    }
    if (!s.ok()) {
      fprintf(stderr, "open error: %s\n", s.ToString().c_str());
      exit(1);
    }
  }

  void Reopen() {
    for (auto cf : column_families_) {
      delete cf;
    }
    column_families_.clear();
    delete db_;
    db_ = nullptr;
#ifndef ROCKSDB_LITE
    txn_db_ = nullptr;
#endif

    num_times_reopened_++;
    auto now = FLAGS_env->NowMicros();
    fprintf(stdout, "%s Reopening database for the %dth time\n",
            FLAGS_env->TimeToString(now/1000000).c_str(),
            num_times_reopened_);
    Open();
  }

  void PrintStatistics() {
    if (dbstats) {
      fprintf(stdout, "STATISTICS:\n%s\n", dbstats->ToString().c_str());
    }
  }

 private:
  std::shared_ptr<Cache> cache_;
  std::shared_ptr<Cache> compressed_cache_;
  std::shared_ptr<const FilterPolicy> filter_policy_;
  DB* db_;
#ifndef ROCKSDB_LITE
  TransactionDB* txn_db_;
#endif
  Options options_;
  std::vector<ColumnFamilyHandle*> column_families_;
  std::vector<std::string> column_family_names_;
  std::atomic<int> new_column_family_name_;
  int num_times_reopened_;
  std::unordered_map<std::string, std::vector<std::string>> options_table_;
  std::vector<std::string> options_index_;
};

}  // namespace rocksdb

int main(int argc, char** argv) {
  SetUsageMessage(std::string("\nUSAGE:\n") + std::string(argv[0]) +
                  " [OPTIONS]...");
  ParseCommandLineFlags(&argc, &argv, true);
#if !defined(NDEBUG) && !defined(OS_MACOSX) && !defined(OS_WIN) && \
  !defined(OS_SOLARIS) && !defined(OS_AIX)
  rocksdb::SyncPoint::GetInstance()->SetCallBack(
      "NewWritableFile:O_DIRECT", [&](void* arg) {
        int* val = static_cast<int*>(arg);
        *val &= ~O_DIRECT;
      });
  rocksdb::SyncPoint::GetInstance()->SetCallBack(
      "NewRandomAccessFile:O_DIRECT", [&](void* arg) {
        int* val = static_cast<int*>(arg);
        *val &= ~O_DIRECT;
      });
  rocksdb::SyncPoint::GetInstance()->EnableProcessing();
#endif

  if (FLAGS_statistics) {
    dbstats = rocksdb::CreateDBStatistics();
  }
  FLAGS_compression_type_e =
    StringToCompressionType(FLAGS_compression_type.c_str());
  FLAGS_checksum_type_e = StringToChecksumType(FLAGS_checksum_type.c_str());
  if (!FLAGS_hdfs.empty()) {
    FLAGS_env  = new rocksdb::HdfsEnv(FLAGS_hdfs);
  }
  FLAGS_rep_factory = StringToRepFactory(FLAGS_memtablerep.c_str());

  // The number of background threads should be at least as much the
  // max number of concurrent compactions.
  FLAGS_env->SetBackgroundThreads(FLAGS_max_background_compactions);
  FLAGS_env->SetBackgroundThreads(FLAGS_num_bottom_pri_threads,
                                  rocksdb::Env::Priority::BOTTOM);
  if (FLAGS_prefixpercent > 0 && FLAGS_prefix_size <= 0) {
    fprintf(stderr,
            "Error: prefixpercent is non-zero while prefix_size is "
            "not positive!\n");
    exit(1);
  }
  if (FLAGS_test_batches_snapshots && FLAGS_prefix_size <= 0) {
    fprintf(stderr,
            "Error: please specify prefix_size for "
            "test_batches_snapshots test!\n");
    exit(1);
  }
  if (FLAGS_memtable_prefix_bloom_size_ratio > 0.0 && FLAGS_prefix_size <= 0) {
    fprintf(stderr,
            "Error: please specify positive prefix_size in order to use "
            "memtable_prefix_bloom_size_ratio\n");
    exit(1);
  }
  if ((FLAGS_readpercent + FLAGS_prefixpercent +
       FLAGS_writepercent + FLAGS_delpercent + FLAGS_delrangepercent +
       FLAGS_iterpercent) != 100) {
      fprintf(stderr,
              "Error: Read+Prefix+Write+Delete+DeleteRange+Iterate percents != "
              "100!\n");
      exit(1);
  }
  if (FLAGS_disable_wal == 1 && FLAGS_reopen > 0) {
      fprintf(stderr, "Error: Db cannot reopen safely with disable_wal set!\n");
      exit(1);
  }
  if ((unsigned)FLAGS_reopen >= FLAGS_ops_per_thread) {
      fprintf(stderr,
              "Error: #DB-reopens should be < ops_per_thread\n"
              "Provided reopens = %d and ops_per_thread = %lu\n",
              FLAGS_reopen,
              (unsigned long)FLAGS_ops_per_thread);
      exit(1);
  }
  if (FLAGS_test_batches_snapshots && FLAGS_delrangepercent > 0) {
    fprintf(stderr, "Error: nonzero delrangepercent unsupported in "
                    "test_batches_snapshots mode\n");
    exit(1);
  }
  if (FLAGS_active_width > FLAGS_max_key) {
    fprintf(stderr, "Error: active_width can be at most max_key\n");
    exit(1);
  } else if (FLAGS_active_width == 0) {
    FLAGS_active_width = FLAGS_max_key;
  }
  if (FLAGS_value_size_mult * kRandomValueMaxFactor > kValueMaxLen) {
    fprintf(stderr, "Error: value_size_mult can be at most %d\n",
            kValueMaxLen / kRandomValueMaxFactor);
    exit(1);
  }
  if (FLAGS_use_merge && FLAGS_nooverwritepercent == 100) {
    fprintf(
        stderr,
        "Error: nooverwritepercent must not be 100 when using merge operands");
    exit(1);
  }

  // Choose a location for the test database if none given with --db=<path>
  if (FLAGS_db.empty()) {
      std::string default_db_path;
      rocksdb::Env::Default()->GetTestDirectory(&default_db_path);
      default_db_path += "/dbstress";
      FLAGS_db = default_db_path;
  }

  rocksdb_kill_odds = FLAGS_kill_random_test;
  rocksdb_kill_prefix_blacklist = SplitString(FLAGS_kill_prefix_blacklist);

  rocksdb::StressTest stress;
  if (stress.Run()) {
    return 0;
  } else {
    return 1;
  }
}

#endif  // GFLAGS