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rocksdb/db/flush_job.cc
Baptiste Lemaire c625b8d017 Add condition on NotifyOnFlushComplete that FlushJob was not mempurge. Add event listeners to mempurge tests. (#8672) 
Summary:
Previously, when a `FlushJob` was redirected to a MemPurge, the function `DBImpl::NotifyOnFlushComplete` was called, which created a series of issues because the JobInfo was not correctly collected from the memtables.
This diff aims at correcting these two issues (`FlushJobInfo` collection in `FlushJob::MemPurge` , no call to `DBImpl::NotifyOnFlushComplete` after successful mempurge).
Event listeners were added to the unit tests to handle these situations.
Surprisingly none of the crashtests caught this issue, I will try to add event listeners to crash tests in the future.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8672

Reviewed By: akankshamahajan15

Differential Revision: D30383109

Pulled By: bjlemaire

fbshipit-source-id: 35a8d4295886923ee4049a6447f00022cb221c73
2021-08-18 17:40:01 -07:00

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// 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.
#include "db/flush_job.h"
#include <cinttypes>
#include <algorithm>
#include <vector>
#include "db/builder.h"
#include "db/db_iter.h"
#include "db/dbformat.h"
#include "db/event_helpers.h"
#include "db/log_reader.h"
#include "db/log_writer.h"
#include "db/memtable.h"
#include "db/memtable_list.h"
#include "db/merge_context.h"
#include "db/range_tombstone_fragmenter.h"
#include "db/version_set.h"
#include "file/file_util.h"
#include "file/filename.h"
#include "logging/event_logger.h"
#include "logging/log_buffer.h"
#include "logging/logging.h"
#include "monitoring/iostats_context_imp.h"
#include "monitoring/perf_context_imp.h"
#include "monitoring/thread_status_util.h"
#include "port/port.h"
#include "rocksdb/db.h"
#include "rocksdb/env.h"
#include "rocksdb/statistics.h"
#include "rocksdb/status.h"
#include "rocksdb/table.h"
#include "table/merging_iterator.h"
#include "table/table_builder.h"
#include "table/two_level_iterator.h"
#include "test_util/sync_point.h"
#include "util/coding.h"
#include "util/mutexlock.h"
#include "util/stop_watch.h"
namespace ROCKSDB_NAMESPACE {
const char* GetFlushReasonString (FlushReason flush_reason) {
switch (flush_reason) {
case FlushReason::kOthers:
return "Other Reasons";
case FlushReason::kGetLiveFiles:
return "Get Live Files";
case FlushReason::kShutDown:
return "Shut down";
case FlushReason::kExternalFileIngestion:
return "External File Ingestion";
case FlushReason::kManualCompaction:
return "Manual Compaction";
case FlushReason::kWriteBufferManager:
return "Write Buffer Manager";
case FlushReason::kWriteBufferFull:
return "Write Buffer Full";
case FlushReason::kTest:
return "Test";
case FlushReason::kDeleteFiles:
return "Delete Files";
case FlushReason::kAutoCompaction:
return "Auto Compaction";
case FlushReason::kManualFlush:
return "Manual Flush";
case FlushReason::kErrorRecovery:
return "Error Recovery";
case FlushReason::kWalFull:
return "WAL Full";
default:
return "Invalid";
}
}
FlushJob::FlushJob(
const std::string& dbname, ColumnFamilyData* cfd,
const ImmutableDBOptions& db_options,
const MutableCFOptions& mutable_cf_options, uint64_t max_memtable_id,
const FileOptions& file_options, VersionSet* versions,
InstrumentedMutex* db_mutex, std::atomic<bool>* shutting_down,
std::vector<SequenceNumber> existing_snapshots,
SequenceNumber earliest_write_conflict_snapshot,
SnapshotChecker* snapshot_checker, JobContext* job_context,
LogBuffer* log_buffer, FSDirectory* db_directory,
FSDirectory* output_file_directory, CompressionType output_compression,
Statistics* stats, EventLogger* event_logger, bool measure_io_stats,
const bool sync_output_directory, const bool write_manifest,
Env::Priority thread_pri, const std::shared_ptr<IOTracer>& io_tracer,
const std::string& db_id, const std::string& db_session_id,
std::string full_history_ts_low, BlobFileCompletionCallback* blob_callback)
: dbname_(dbname),
db_id_(db_id),
db_session_id_(db_session_id),
cfd_(cfd),
db_options_(db_options),
mutable_cf_options_(mutable_cf_options),
max_memtable_id_(max_memtable_id),
file_options_(file_options),
versions_(versions),
db_mutex_(db_mutex),
shutting_down_(shutting_down),
existing_snapshots_(std::move(existing_snapshots)),
earliest_write_conflict_snapshot_(earliest_write_conflict_snapshot),
snapshot_checker_(snapshot_checker),
job_context_(job_context),
log_buffer_(log_buffer),
db_directory_(db_directory),
output_file_directory_(output_file_directory),
output_compression_(output_compression),
stats_(stats),
event_logger_(event_logger),
measure_io_stats_(measure_io_stats),
sync_output_directory_(sync_output_directory),
write_manifest_(write_manifest),
edit_(nullptr),
base_(nullptr),
pick_memtable_called(false),
thread_pri_(thread_pri),
io_tracer_(io_tracer),
clock_(db_options_.clock),
full_history_ts_low_(std::move(full_history_ts_low)),
blob_callback_(blob_callback) {
// Update the thread status to indicate flush.
ReportStartedFlush();
TEST_SYNC_POINT("FlushJob::FlushJob()");
}
FlushJob::~FlushJob() {
io_status_.PermitUncheckedError();
ThreadStatusUtil::ResetThreadStatus();
}
void FlushJob::ReportStartedFlush() {
ThreadStatusUtil::SetColumnFamily(cfd_, cfd_->ioptions()->env,
db_options_.enable_thread_tracking);
ThreadStatusUtil::SetThreadOperation(ThreadStatus::OP_FLUSH);
ThreadStatusUtil::SetThreadOperationProperty(
ThreadStatus::COMPACTION_JOB_ID,
job_context_->job_id);
IOSTATS_RESET(bytes_written);
}
void FlushJob::ReportFlushInputSize(const autovector<MemTable*>& mems) {
uint64_t input_size = 0;
for (auto* mem : mems) {
input_size += mem->ApproximateMemoryUsage();
}
ThreadStatusUtil::IncreaseThreadOperationProperty(
ThreadStatus::FLUSH_BYTES_MEMTABLES,
input_size);
}
void FlushJob::RecordFlushIOStats() {
RecordTick(stats_, FLUSH_WRITE_BYTES, IOSTATS(bytes_written));
ThreadStatusUtil::IncreaseThreadOperationProperty(
ThreadStatus::FLUSH_BYTES_WRITTEN, IOSTATS(bytes_written));
IOSTATS_RESET(bytes_written);
}
void FlushJob::PickMemTable() {
db_mutex_->AssertHeld();
assert(!pick_memtable_called);
pick_memtable_called = true;
// Save the contents of the earliest memtable as a new Table
cfd_->imm()->PickMemtablesToFlush(max_memtable_id_, &mems_);
if (mems_.empty()) {
return;
}
ReportFlushInputSize(mems_);
// entries mems are (implicitly) sorted in ascending order by their created
// time. We will use the first memtable's `edit` to keep the meta info for
// this flush.
MemTable* m = mems_[0];
edit_ = m->GetEdits();
edit_->SetPrevLogNumber(0);
// SetLogNumber(log_num) indicates logs with number smaller than log_num
// will no longer be picked up for recovery.
edit_->SetLogNumber(mems_.back()->GetNextLogNumber());
edit_->SetColumnFamily(cfd_->GetID());
// path 0 for level 0 file.
meta_.fd = FileDescriptor(versions_->NewFileNumber(), 0, 0);
base_ = cfd_->current();
base_->Ref(); // it is likely that we do not need this reference
}
Status FlushJob::Run(LogsWithPrepTracker* prep_tracker, FileMetaData* file_meta,
bool* switched_to_mempurge) {
TEST_SYNC_POINT("FlushJob::Start");
db_mutex_->AssertHeld();
assert(pick_memtable_called);
AutoThreadOperationStageUpdater stage_run(
ThreadStatus::STAGE_FLUSH_RUN);
if (mems_.empty()) {
ROCKS_LOG_BUFFER(log_buffer_, "[%s] Nothing in memtable to flush",
cfd_->GetName().c_str());
return Status::OK();
}
// I/O measurement variables
PerfLevel prev_perf_level = PerfLevel::kEnableTime;
uint64_t prev_write_nanos = 0;
uint64_t prev_fsync_nanos = 0;
uint64_t prev_range_sync_nanos = 0;
uint64_t prev_prepare_write_nanos = 0;
uint64_t prev_cpu_write_nanos = 0;
uint64_t prev_cpu_read_nanos = 0;
if (measure_io_stats_) {
prev_perf_level = GetPerfLevel();
SetPerfLevel(PerfLevel::kEnableTime);
prev_write_nanos = IOSTATS(write_nanos);
prev_fsync_nanos = IOSTATS(fsync_nanos);
prev_range_sync_nanos = IOSTATS(range_sync_nanos);
prev_prepare_write_nanos = IOSTATS(prepare_write_nanos);
prev_cpu_write_nanos = IOSTATS(cpu_write_nanos);
prev_cpu_read_nanos = IOSTATS(cpu_read_nanos);
}
Status mempurge_s = Status::NotFound("No MemPurge.");
if ((db_options_.experimental_mempurge_threshold > 0.0) &&
(cfd_->GetFlushReason() == FlushReason::kWriteBufferFull) &&
(!mems_.empty()) && MemPurgeDecider()) {
mempurge_s = MemPurge();
if (!mempurge_s.ok()) {
// Mempurge is typically aborted when the output
// bytes cannot be contained onto a single output memtable.
if (mempurge_s.IsAborted()) {
ROCKS_LOG_INFO(db_options_.info_log, "Mempurge process aborted: %s\n",
mempurge_s.ToString().c_str());
} else {
// However the mempurge process can also fail for
// other reasons (eg: new_mem->Add() fails).
ROCKS_LOG_WARN(db_options_.info_log, "Mempurge process failed: %s\n",
mempurge_s.ToString().c_str());
}
} else {
if (switched_to_mempurge) {
*switched_to_mempurge = true;
} else {
// The mempurge process was successful, but no switch_to_mempurge
// pointer provided so no way to propagate the state of flush job.
ROCKS_LOG_WARN(db_options_.info_log,
"Mempurge process succeeded"
"but no 'switched_to_mempurge' ptr provided.\n");
}
}
}
Status s;
if (mempurge_s.ok()) {
base_->Unref();
s = Status::OK();
} else {
// This will release and re-acquire the mutex.
s = WriteLevel0Table();
}
if (s.ok() && cfd_->IsDropped()) {
s = Status::ColumnFamilyDropped("Column family dropped during compaction");
}
if ((s.ok() || s.IsColumnFamilyDropped()) &&
shutting_down_->load(std::memory_order_acquire)) {
s = Status::ShutdownInProgress("Database shutdown");
}
if (!s.ok()) {
cfd_->imm()->RollbackMemtableFlush(mems_, meta_.fd.GetNumber());
} else if (write_manifest_) {
TEST_SYNC_POINT("FlushJob::InstallResults");
// Replace immutable memtable with the generated Table
IOStatus tmp_io_s;
s = cfd_->imm()->TryInstallMemtableFlushResults(
cfd_, mutable_cf_options_, mems_, prep_tracker, versions_, db_mutex_,
meta_.fd.GetNumber(), &job_context_->memtables_to_free, db_directory_,
log_buffer_, &committed_flush_jobs_info_, &tmp_io_s,
!(mempurge_s.ok()) /* write_edit : true if no mempurge happened (or if aborted),
but 'false' if mempurge successful: no new min log number
or new level 0 file path to write to manifest. */);
if (!tmp_io_s.ok()) {
io_status_ = tmp_io_s;
}
}
if (s.ok() && file_meta != nullptr) {
*file_meta = meta_;
}
RecordFlushIOStats();
// When measure_io_stats_ is true, the default 512 bytes is not enough.
auto stream = event_logger_->LogToBuffer(log_buffer_, 1024);
stream << "job" << job_context_->job_id << "event"
<< "flush_finished";
stream << "output_compression"
<< CompressionTypeToString(output_compression_);
stream << "lsm_state";
stream.StartArray();
auto vstorage = cfd_->current()->storage_info();
for (int level = 0; level < vstorage->num_levels(); ++level) {
stream << vstorage->NumLevelFiles(level);
}
stream.EndArray();
const auto& blob_files = vstorage->GetBlobFiles();
if (!blob_files.empty()) {
stream << "blob_file_head" << blob_files.begin()->first;
stream << "blob_file_tail" << blob_files.rbegin()->first;
}
stream << "immutable_memtables" << cfd_->imm()->NumNotFlushed();
if (measure_io_stats_) {
if (prev_perf_level != PerfLevel::kEnableTime) {
SetPerfLevel(prev_perf_level);
}
stream << "file_write_nanos" << (IOSTATS(write_nanos) - prev_write_nanos);
stream << "file_range_sync_nanos"
<< (IOSTATS(range_sync_nanos) - prev_range_sync_nanos);
stream << "file_fsync_nanos" << (IOSTATS(fsync_nanos) - prev_fsync_nanos);
stream << "file_prepare_write_nanos"
<< (IOSTATS(prepare_write_nanos) - prev_prepare_write_nanos);
stream << "file_cpu_write_nanos"
<< (IOSTATS(cpu_write_nanos) - prev_cpu_write_nanos);
stream << "file_cpu_read_nanos"
<< (IOSTATS(cpu_read_nanos) - prev_cpu_read_nanos);
}
return s;
}
void FlushJob::Cancel() {
db_mutex_->AssertHeld();
assert(base_ != nullptr);
base_->Unref();
}
Status FlushJob::MemPurge() {
Status s;
db_mutex_->AssertHeld();
db_mutex_->Unlock();
assert(!mems_.empty());
// Measure purging time.
const uint64_t start_micros = clock_->NowMicros();
const uint64_t start_cpu_micros = clock_->CPUNanos() / 1000;
MemTable* new_mem = nullptr;
// For performance/log investigation purposes:
// look at how much useful payload we harvest in the new_mem.
// This value is then printed to the DB log.
double new_mem_capacity = 0.0;
// Create two iterators, one for the memtable data (contains
// info from puts + deletes), and one for the memtable
// Range Tombstones (from DeleteRanges).
ReadOptions ro;
ro.total_order_seek = true;
Arena arena;
std::vector<InternalIterator*> memtables;
std::vector<std::unique_ptr<FragmentedRangeTombstoneIterator>>
range_del_iters;
for (MemTable* m : mems_) {
memtables.push_back(m->NewIterator(ro, &arena));
auto* range_del_iter = m->NewRangeTombstoneIterator(ro, kMaxSequenceNumber);
if (range_del_iter != nullptr) {
range_del_iters.emplace_back(range_del_iter);
}
}
assert(!memtables.empty());
SequenceNumber first_seqno = kMaxSequenceNumber;
SequenceNumber earliest_seqno = kMaxSequenceNumber;
// Pick first and earliest seqno as min of all first_seqno
// and earliest_seqno of the mempurged memtables.
for (const auto& mem : mems_) {
first_seqno = mem->GetFirstSequenceNumber() < first_seqno
? mem->GetFirstSequenceNumber()
: first_seqno;
earliest_seqno = mem->GetEarliestSequenceNumber() < earliest_seqno
? mem->GetEarliestSequenceNumber()
: earliest_seqno;
}
ScopedArenaIterator iter(
NewMergingIterator(&(cfd_->internal_comparator()), memtables.data(),
static_cast<int>(memtables.size()), &arena));
auto* ioptions = cfd_->ioptions();
// Place iterator at the First (meaning most recent) key node.
iter->SeekToFirst();
std::unique_ptr<CompactionRangeDelAggregator> range_del_agg(
new CompactionRangeDelAggregator(&(cfd_->internal_comparator()),
existing_snapshots_));
for (auto& rd_iter : range_del_iters) {
range_del_agg->AddTombstones(std::move(rd_iter));
}
// If there is valid data in the memtable,
// or at least range tombstones, copy over the info
// to the new memtable.
if (iter->Valid() || !range_del_agg->IsEmpty()) {
// MaxSize is the size of a memtable.
size_t maxSize = mutable_cf_options_.write_buffer_size;
std::unique_ptr<CompactionFilter> compaction_filter;
if (ioptions->compaction_filter_factory != nullptr &&
ioptions->compaction_filter_factory->ShouldFilterTableFileCreation(
TableFileCreationReason::kFlush)) {
CompactionFilter::Context ctx;
ctx.is_full_compaction = false;
ctx.is_manual_compaction = false;
ctx.column_family_id = cfd_->GetID();
ctx.reason = TableFileCreationReason::kFlush;
compaction_filter =
ioptions->compaction_filter_factory->CreateCompactionFilter(ctx);
if (compaction_filter != nullptr &&
!compaction_filter->IgnoreSnapshots()) {
s = Status::NotSupported(
"CompactionFilter::IgnoreSnapshots() = false is not supported "
"anymore.");
return s;
}
}
new_mem = new MemTable((cfd_->internal_comparator()), *(cfd_->ioptions()),
mutable_cf_options_, cfd_->write_buffer_mgr(),
earliest_seqno, cfd_->GetID());
assert(new_mem != nullptr);
Env* env = db_options_.env;
assert(env);
MergeHelper merge(
env, (cfd_->internal_comparator()).user_comparator(),
(ioptions->merge_operator).get(), compaction_filter.get(),
ioptions->logger, true /* internal key corruption is not ok */,
existing_snapshots_.empty() ? 0 : existing_snapshots_.back(),
snapshot_checker_);
CompactionIterator c_iter(
iter.get(), (cfd_->internal_comparator()).user_comparator(), &merge,
kMaxSequenceNumber, &existing_snapshots_,
earliest_write_conflict_snapshot_, snapshot_checker_, env,
ShouldReportDetailedTime(env, ioptions->stats),
true /* internal key corruption is not ok */, range_del_agg.get(),
nullptr, ioptions->allow_data_in_errors,
/*compaction=*/nullptr, compaction_filter.get(),
/*shutting_down=*/nullptr,
/*preserve_deletes_seqnum=*/0, /*manual_compaction_paused=*/nullptr,
/*manual_compaction_canceled=*/nullptr, ioptions->info_log,
&(cfd_->GetFullHistoryTsLow()));
// Set earliest sequence number in the new memtable
// to be equal to the earliest sequence number of the
// memtable being flushed (See later if there is a need
// to update this number!).
new_mem->SetEarliestSequenceNumber(earliest_seqno);
// Likewise for first seq number.
new_mem->SetFirstSequenceNumber(first_seqno);
SequenceNumber new_first_seqno = kMaxSequenceNumber;
c_iter.SeekToFirst();
// Key transfer
for (; c_iter.Valid(); c_iter.Next()) {
const ParsedInternalKey ikey = c_iter.ikey();
const Slice value = c_iter.value();
new_first_seqno =
ikey.sequence < new_first_seqno ? ikey.sequence : new_first_seqno;
// Should we update "OldestKeyTime" ???? -> timestamp appear
// to still be an "experimental" feature.
s = new_mem->Add(
ikey.sequence, ikey.type, ikey.user_key, value,
nullptr, // KV protection info set as nullptr since it
// should only be useful for the first add to
// the original memtable.
false, // : allow concurrent_memtable_writes_
// Not seen as necessary for now.
nullptr, // get_post_process_info(m) must be nullptr
// when concurrent_memtable_writes is switched off.
nullptr); // hint, only used when concurrent_memtable_writes_
// is switched on.
if (!s.ok()) {
break;
}
// If new_mem has size greater than maxSize,
// then rollback to regular flush operation,
// and destroy new_mem.
if (new_mem->ApproximateMemoryUsage() > maxSize) {
s = Status::Aborted("Mempurge filled more than one memtable.");
new_mem_capacity = 1.0;
break;
}
}
// Check status and propagate
// potential error status from c_iter
if (!s.ok()) {
c_iter.status().PermitUncheckedError();
} else if (!c_iter.status().ok()) {
s = c_iter.status();
}
// Range tombstone transfer.
if (s.ok()) {
auto range_del_it = range_del_agg->NewIterator();
for (range_del_it->SeekToFirst(); range_del_it->Valid();
range_del_it->Next()) {
auto tombstone = range_del_it->Tombstone();
new_first_seqno =
tombstone.seq_ < new_first_seqno ? tombstone.seq_ : new_first_seqno;
s = new_mem->Add(
tombstone.seq_, // Sequence number
kTypeRangeDeletion, // KV type
tombstone.start_key_, // Key is start key.
tombstone.end_key_, // Value is end key.
nullptr, // KV protection info set as nullptr since it
// should only be useful for the first add to
// the original memtable.
false, // : allow concurrent_memtable_writes_
// Not seen as necessary for now.
nullptr, // get_post_process_info(m) must be nullptr
// when concurrent_memtable_writes is switched off.
nullptr); // hint, only used when concurrent_memtable_writes_
// is switched on.
if (!s.ok()) {
break;
}
// If new_mem has size greater than maxSize,
// then rollback to regular flush operation,
// and destroy new_mem.
if (new_mem->ApproximateMemoryUsage() > maxSize) {
s = Status::Aborted(Slice("Mempurge filled more than one memtable."));
new_mem_capacity = 1.0;
break;
}
}
}
// If everything happened smoothly and new_mem contains valid data,
// decide if it is flushed to storage or kept in the imm()
// memtable list (memory).
if (s.ok() && (new_first_seqno != kMaxSequenceNumber)) {
// Rectify the first sequence number, which (unlike the earliest seq
// number) needs to be present in the new memtable.
new_mem->SetFirstSequenceNumber(new_first_seqno);
// The new_mem is added to the list of immutable memtables
// only if it filled at less than 100% capacity and isn't flagged
// as in need of being flushed.
if (new_mem->ApproximateMemoryUsage() < maxSize &&
!(new_mem->ShouldFlushNow())) {
db_mutex_->Lock();
uint64_t new_mem_id = mems_[0]->GetID();
new_mem->SetID(new_mem_id);
// This addition will not trigger another flush, because
// we do not call SchedulePendingFlush().
cfd_->imm()->Add(new_mem, &job_context_->memtables_to_free);
new_mem->Ref();
#ifndef ROCKSDB_LITE
// Piggyback FlushJobInfo on the first flushed memtable.
db_mutex_->AssertHeld();
meta_.fd.file_size = 0;
mems_[0]->SetFlushJobInfo(GetFlushJobInfo());
#endif // !ROCKSDB_LITE
db_mutex_->Unlock();
} else {
s = Status::Aborted(Slice("Mempurge filled more than one memtable."));
new_mem_capacity = 1.0;
if (new_mem) {
job_context_->memtables_to_free.push_back(new_mem);
}
}
} else {
// In this case, the newly allocated new_mem is empty.
assert(new_mem != nullptr);
job_context_->memtables_to_free.push_back(new_mem);
}
}
// Reacquire the mutex for WriteLevel0 function.
db_mutex_->Lock();
// If mempurge successful, don't write input tables to level0,
// but write any full output table to level0.
if (s.ok()) {
TEST_SYNC_POINT("DBImpl::FlushJob:MemPurgeSuccessful");
} else {
TEST_SYNC_POINT("DBImpl::FlushJob:MemPurgeUnsuccessful");
}
const uint64_t micros = clock_->NowMicros() - start_micros;
const uint64_t cpu_micros = clock_->CPUNanos() / 1000 - start_cpu_micros;
ROCKS_LOG_INFO(db_options_.info_log,
"[%s] [JOB %d] Mempurge lasted %" PRIu64
" microseconds, and %" PRIu64
" cpu "
"microseconds. Status is %s ok. Perc capacity: %f\n",
cfd_->GetName().c_str(), job_context_->job_id, micros,
cpu_micros, s.ok() ? "" : "not", new_mem_capacity);
return s;
}
bool FlushJob::MemPurgeDecider() {
double threshold = db_options_.experimental_mempurge_threshold;
// Never trigger mempurge if threshold is not a strictly positive value.
if (!(threshold > 0.0)) {
return false;
}
if (threshold > (1.0 * mems_.size())) {
return true;
}
// Payload and useful_payload (in bytes).
// The useful payload ratio of a given MemTable
// is estimated to be useful_payload/payload.
uint64_t payload = 0, useful_payload = 0, entry_size = 0;
// Local variables used repetitively inside the for-loop
// when iterating over the sampled entries.
Slice key_slice, value_slice;
ParsedInternalKey res;
SnapshotImpl min_snapshot;
std::string vget;
Status mget_s, parse_s;
MergeContext merge_context;
SequenceNumber max_covering_tombstone_seq = 0, sqno = 0,
min_seqno_snapshot = 0;
bool get_res, can_be_useful_payload, not_in_next_mems;
// If estimated_useful_payload is > threshold,
// then flush to storage, else MemPurge.
double estimated_useful_payload = 0.0;
// Cochran formula for determining sample size.
// 95% confidence interval, 7% precision.
// n0 = (1.96*1.96)*0.25/(0.07*0.07) = 196.0
double n0 = 196.0;
ReadOptions ro;
ro.total_order_seek = true;
// Iterate over each memtable of the set.
for (auto mem_iter = std::begin(mems_); mem_iter != std::end(mems_);
mem_iter++) {
MemTable* mt = *mem_iter;
// Else sample from the table.
uint64_t nentries = mt->num_entries();
// Corrected Cochran formula for small populations
// (converges to n0 for large populations).
uint64_t target_sample_size =
static_cast<uint64_t>(ceil(n0 / (1.0 + (n0 / nentries))));
std::unordered_set<const char*> sentries = {};
// Populate sample entries set.
mt->UniqueRandomSample(target_sample_size, &sentries);
// Estimate the garbage ratio by comparing if
// each sample corresponds to a valid entry.
for (const char* ss : sentries) {
key_slice = GetLengthPrefixedSlice(ss);
parse_s = ParseInternalKey(key_slice, &res, true /*log_err_key*/);
if (!parse_s.ok()) {
ROCKS_LOG_WARN(db_options_.info_log,
"Memtable Decider: ParseInternalKey did not parse "
"key_slice %s successfully.",
key_slice.data());
}
// Size of the entry is "key size (+ value size if KV entry)"
entry_size = key_slice.size();
if (res.type == kTypeValue) {
value_slice =
GetLengthPrefixedSlice(key_slice.data() + key_slice.size());
entry_size += value_slice.size();
}
// Count entry bytes as payload.
payload += entry_size;
LookupKey lkey(res.user_key, kMaxSequenceNumber);
// Paranoia: zero out these values just in case.
max_covering_tombstone_seq = 0;
sqno = 0;
// Pick the oldest existing snapshot that is more recent
// than the sequence number of the sampled entry.
min_seqno_snapshot = kMaxSequenceNumber;
for (SequenceNumber seq_num : existing_snapshots_) {
if (seq_num > res.sequence && seq_num < min_seqno_snapshot) {
min_seqno_snapshot = seq_num;
}
}
min_snapshot.number_ = min_seqno_snapshot;
ro.snapshot =
min_seqno_snapshot < kMaxSequenceNumber ? &min_snapshot : nullptr;
// Estimate if the sample entry is valid or not.
get_res = mt->Get(lkey, &vget, nullptr, &mget_s, &merge_context,
&max_covering_tombstone_seq, &sqno, ro);
if (!get_res) {
ROCKS_LOG_WARN(
db_options_.info_log,
"Memtable Get returned false when Get(sampled entry). "
"Yet each sample entry should exist somewhere in the memtable, "
"unrelated to whether it has been deleted or not.");
}
// TODO(bjlemaire): evaluate typeMerge.
// This is where the sampled entry is estimated to be
// garbage or not. Note that this is a garbage *estimation*
// because we do not include certain items such as
// CompactionFitlers triggered at flush, or if the same delete
// has been inserted twice or more in the memtable.
// Evaluate if the entry can be useful payload
// Situation #1: entry is a KV entry, was found in the memtable mt
// and the sequence numbers match.
can_be_useful_payload = (res.type == kTypeValue) && get_res &&
mget_s.ok() && (sqno == res.sequence);
// Situation #2: entry is a delete entry, was found in the memtable mt
// (because gres==true) and no valid KV entry is found.
// (note: duplicate delete entries are also taken into
// account here, because the sequence number 'sqno'
// in memtable->Get(&sqno) operation is set to be equal
// to the most recent delete entry as well).
can_be_useful_payload |=
((res.type == kTypeDeletion) || (res.type == kTypeSingleDeletion)) &&
mget_s.IsNotFound() && get_res && (sqno == res.sequence);
// If there is a chance that the entry is useful payload
// Verify that the entry does not appear in the following memtables
// (memtables with greater memtable ID/larger sequence numbers).
if (can_be_useful_payload) {
not_in_next_mems = true;
for (auto next_mem_iter = mem_iter + 1;
next_mem_iter != std::end(mems_); next_mem_iter++) {
if ((*next_mem_iter)
->Get(lkey, &vget, nullptr, &mget_s, &merge_context,
&max_covering_tombstone_seq, &sqno, ro)) {
not_in_next_mems = false;
break;
}
}
if (not_in_next_mems) {
useful_payload += entry_size;
}
}
}
if (payload > 0) {
// We use the estimated useful payload ratio to
// evaluate how many of the memtable bytes are useful bytes.
estimated_useful_payload +=
(mt->ApproximateMemoryUsage()) * (useful_payload * 1.0 / payload);
ROCKS_LOG_INFO(
db_options_.info_log,
"Mempurge sampling - found garbage ratio from sampling: %f.\n",
(payload - useful_payload) * 1.0 / payload);
} else {
ROCKS_LOG_WARN(db_options_.info_log,
"Mempurge sampling: null payload measured, and collected "
"sample size is %zu\n.",
sentries.size());
}
}
// We convert the total number of useful payload bytes
// into the proportion of memtable necessary to store all these bytes.
// We compare this proportion with the threshold value.
return ((estimated_useful_payload / mutable_cf_options_.write_buffer_size) <
threshold);
}
Status FlushJob::WriteLevel0Table() {
AutoThreadOperationStageUpdater stage_updater(
ThreadStatus::STAGE_FLUSH_WRITE_L0);
db_mutex_->AssertHeld();
const uint64_t start_micros = clock_->NowMicros();
const uint64_t start_cpu_micros = clock_->CPUNanos() / 1000;
Status s;
std::vector<BlobFileAddition> blob_file_additions;
{
auto write_hint = cfd_->CalculateSSTWriteHint(0);
db_mutex_->Unlock();
if (log_buffer_) {
log_buffer_->FlushBufferToLog();
}
// memtables and range_del_iters store internal iterators over each data
// memtable and its associated range deletion memtable, respectively, at
// corresponding indexes.
std::vector<InternalIterator*> memtables;
std::vector<std::unique_ptr<FragmentedRangeTombstoneIterator>>
range_del_iters;
ReadOptions ro;
ro.total_order_seek = true;
Arena arena;
uint64_t total_num_entries = 0, total_num_deletes = 0;
uint64_t total_data_size = 0;
size_t total_memory_usage = 0;
for (MemTable* m : mems_) {
ROCKS_LOG_INFO(
db_options_.info_log,
"[%s] [JOB %d] Flushing memtable with next log file: %" PRIu64 "\n",
cfd_->GetName().c_str(), job_context_->job_id, m->GetNextLogNumber());
memtables.push_back(m->NewIterator(ro, &arena));
auto* range_del_iter =
m->NewRangeTombstoneIterator(ro, kMaxSequenceNumber);
if (range_del_iter != nullptr) {
range_del_iters.emplace_back(range_del_iter);
}
total_num_entries += m->num_entries();
total_num_deletes += m->num_deletes();
total_data_size += m->get_data_size();
total_memory_usage += m->ApproximateMemoryUsage();
}
event_logger_->Log() << "job" << job_context_->job_id << "event"
<< "flush_started"
<< "num_memtables" << mems_.size() << "num_entries"
<< total_num_entries << "num_deletes"
<< total_num_deletes << "total_data_size"
<< total_data_size << "memory_usage"
<< total_memory_usage << "flush_reason"
<< GetFlushReasonString(cfd_->GetFlushReason());
{
ScopedArenaIterator iter(
NewMergingIterator(&cfd_->internal_comparator(), memtables.data(),
static_cast<int>(memtables.size()), &arena));
ROCKS_LOG_INFO(db_options_.info_log,
"[%s] [JOB %d] Level-0 flush table #%" PRIu64 ": started",
cfd_->GetName().c_str(), job_context_->job_id,
meta_.fd.GetNumber());
TEST_SYNC_POINT_CALLBACK("FlushJob::WriteLevel0Table:output_compression",
&output_compression_);
int64_t _current_time = 0;
auto status = clock_->GetCurrentTime(&_current_time);
// Safe to proceed even if GetCurrentTime fails. So, log and proceed.
if (!status.ok()) {
ROCKS_LOG_WARN(
db_options_.info_log,
"Failed to get current time to populate creation_time property. "
"Status: %s",
status.ToString().c_str());
}
const uint64_t current_time = static_cast<uint64_t>(_current_time);
uint64_t oldest_key_time =
mems_.front()->ApproximateOldestKeyTime();
// It's not clear whether oldest_key_time is always available. In case
// it is not available, use current_time.
uint64_t oldest_ancester_time = std::min(current_time, oldest_key_time);
TEST_SYNC_POINT_CALLBACK(
"FlushJob::WriteLevel0Table:oldest_ancester_time",
&oldest_ancester_time);
meta_.oldest_ancester_time = oldest_ancester_time;
meta_.file_creation_time = current_time;
uint64_t creation_time = (cfd_->ioptions()->compaction_style ==
CompactionStyle::kCompactionStyleFIFO)
? current_time
: meta_.oldest_ancester_time;
uint64_t num_input_entries = 0;
uint64_t memtable_payload_bytes = 0;
uint64_t memtable_garbage_bytes = 0;
IOStatus io_s;
const std::string* const full_history_ts_low =
(full_history_ts_low_.empty()) ? nullptr : &full_history_ts_low_;
TableBuilderOptions tboptions(
*cfd_->ioptions(), mutable_cf_options_, cfd_->internal_comparator(),
cfd_->int_tbl_prop_collector_factories(), output_compression_,
mutable_cf_options_.compression_opts, cfd_->GetID(), cfd_->GetName(),
0 /* level */, false /* is_bottommost */,
TableFileCreationReason::kFlush, creation_time, oldest_key_time,
current_time, db_id_, db_session_id_, 0 /* target_file_size */,
meta_.fd.GetNumber());
s = BuildTable(
dbname_, versions_, db_options_, tboptions, file_options_,
cfd_->table_cache(), iter.get(), std::move(range_del_iters), &meta_,
&blob_file_additions, existing_snapshots_,
earliest_write_conflict_snapshot_, snapshot_checker_,
mutable_cf_options_.paranoid_file_checks, cfd_->internal_stats(),
&io_s, io_tracer_, event_logger_, job_context_->job_id, Env::IO_HIGH,
&table_properties_, write_hint, full_history_ts_low, blob_callback_,
&num_input_entries, &memtable_payload_bytes, &memtable_garbage_bytes);
if (!io_s.ok()) {
io_status_ = io_s;
}
if (num_input_entries != total_num_entries && s.ok()) {
std::string msg = "Expected " + ToString(total_num_entries) +
" entries in memtables, but read " +
ToString(num_input_entries);
ROCKS_LOG_WARN(db_options_.info_log, "[%s] [JOB %d] Level-0 flush %s",
cfd_->GetName().c_str(), job_context_->job_id,
msg.c_str());
if (db_options_.flush_verify_memtable_count) {
s = Status::Corruption(msg);
}
}
if (tboptions.reason == TableFileCreationReason::kFlush) {
TEST_SYNC_POINT("DBImpl::FlushJob:Flush");
RecordTick(stats_, MEMTABLE_PAYLOAD_BYTES_AT_FLUSH,
memtable_payload_bytes);
RecordTick(stats_, MEMTABLE_GARBAGE_BYTES_AT_FLUSH,
memtable_garbage_bytes);
}
LogFlush(db_options_.info_log);
}
ROCKS_LOG_INFO(db_options_.info_log,
"[%s] [JOB %d] Level-0 flush table #%" PRIu64 ": %" PRIu64
" bytes %s"
"%s",
cfd_->GetName().c_str(), job_context_->job_id,
meta_.fd.GetNumber(), meta_.fd.GetFileSize(),
s.ToString().c_str(),
meta_.marked_for_compaction ? " (needs compaction)" : "");
if (s.ok() && output_file_directory_ != nullptr && sync_output_directory_) {
s = output_file_directory_->Fsync(IOOptions(), nullptr);
}
TEST_SYNC_POINT_CALLBACK("FlushJob::WriteLevel0Table", &mems_);
db_mutex_->Lock();
}
base_->Unref();
// Note that if file_size is zero, the file has been deleted and
// should not be added to the manifest.
const bool has_output = meta_.fd.GetFileSize() > 0;
if (s.ok() && has_output) {
TEST_SYNC_POINT("DBImpl::FlushJob:SSTFileCreated");
// if we have more than 1 background thread, then we cannot
// insert files directly into higher levels because some other
// threads could be concurrently producing compacted files for
// that key range.
// Add file to L0
edit_->AddFile(0 /* level */, meta_.fd.GetNumber(), meta_.fd.GetPathId(),
meta_.fd.GetFileSize(), meta_.smallest, meta_.largest,
meta_.fd.smallest_seqno, meta_.fd.largest_seqno,
meta_.marked_for_compaction, meta_.oldest_blob_file_number,
meta_.oldest_ancester_time, meta_.file_creation_time,
meta_.file_checksum, meta_.file_checksum_func_name);
edit_->SetBlobFileAdditions(std::move(blob_file_additions));
}
#ifndef ROCKSDB_LITE
// Piggyback FlushJobInfo on the first first flushed memtable.
mems_[0]->SetFlushJobInfo(GetFlushJobInfo());
#endif // !ROCKSDB_LITE
// Note that here we treat flush as level 0 compaction in internal stats
InternalStats::CompactionStats stats(CompactionReason::kFlush, 1);
const uint64_t micros = clock_->NowMicros() - start_micros;
const uint64_t cpu_micros = clock_->CPUNanos() / 1000 - start_cpu_micros;
stats.micros = micros;
stats.cpu_micros = cpu_micros;
ROCKS_LOG_INFO(db_options_.info_log,
"[%s] [JOB %d] Flush lasted %" PRIu64
" microseconds, and %" PRIu64 " cpu microseconds.\n",
cfd_->GetName().c_str(), job_context_->job_id, micros,
cpu_micros);
if (has_output) {
stats.bytes_written = meta_.fd.GetFileSize();
stats.num_output_files = 1;
}
const auto& blobs = edit_->GetBlobFileAdditions();
for (const auto& blob : blobs) {
stats.bytes_written_blob += blob.GetTotalBlobBytes();
}
stats.num_output_files_blob = static_cast<int>(blobs.size());
RecordTimeToHistogram(stats_, FLUSH_TIME, stats.micros);
cfd_->internal_stats()->AddCompactionStats(0 /* level */, thread_pri_, stats);
cfd_->internal_stats()->AddCFStats(
InternalStats::BYTES_FLUSHED,
stats.bytes_written + stats.bytes_written_blob);
RecordFlushIOStats();
return s;
}
#ifndef ROCKSDB_LITE
std::unique_ptr<FlushJobInfo> FlushJob::GetFlushJobInfo() const {
db_mutex_->AssertHeld();
std::unique_ptr<FlushJobInfo> info(new FlushJobInfo{});
info->cf_id = cfd_->GetID();
info->cf_name = cfd_->GetName();
const uint64_t file_number = meta_.fd.GetNumber();
info->file_path =
MakeTableFileName(cfd_->ioptions()->cf_paths[0].path, file_number);
info->file_number = file_number;
info->oldest_blob_file_number = meta_.oldest_blob_file_number;
info->thread_id = db_options_.env->GetThreadID();
info->job_id = job_context_->job_id;
info->smallest_seqno = meta_.fd.smallest_seqno;
info->largest_seqno = meta_.fd.largest_seqno;
info->table_properties = table_properties_;
info->flush_reason = cfd_->GetFlushReason();
return info;
}
#endif // !ROCKSDB_LITE
} // namespace ROCKSDB_NAMESPACE
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