rocksdb/trace_replay/block_cache_tracer.h
haoyuhuang 8a008d4170 Block access tracing: Trace referenced key for Get on non-data blocks. (#5548)
Summary:
This PR traces the referenced key for Get for all types of blocks. This is useful when evaluating hybrid row-block caches.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5548

Test Plan: make clean && USE_CLANG=1 make check -j32

Differential Revision: D16157979

Pulled By: HaoyuHuang

fbshipit-source-id: f6327411c9deb74e35e22a35f66cdbae09ab9d87
2019-07-17 13:05:58 -07:00

246 lines
9.2 KiB
C++

// 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).
#pragma once
#include <atomic>
#include "monitoring/instrumented_mutex.h"
#include "rocksdb/env.h"
#include "rocksdb/options.h"
#include "rocksdb/trace_reader_writer.h"
#include "table/table_reader_caller.h"
#include "trace_replay/trace_replay.h"
namespace rocksdb {
extern const uint64_t kMicrosInSecond;
extern const uint64_t kSecondInMinute;
extern const uint64_t kSecondInHour;
class BlockCacheTraceHelper {
public:
static bool IsGetOrMultiGetOnDataBlock(TraceType block_type,
TableReaderCaller caller);
static bool IsGetOrMultiGet(TableReaderCaller caller);
static bool IsUserAccess(TableReaderCaller caller);
static const std::string kUnknownColumnFamilyName;
static const uint64_t kReservedGetId;
};
// Lookup context for tracing block cache accesses.
// We trace block accesses at five places:
// 1. BlockBasedTable::GetFilter
// 2. BlockBasedTable::GetUncompressedDict.
// 3. BlockBasedTable::MaybeReadAndLoadToCache. (To trace access on data, index,
// and range deletion block.)
// 4. BlockBasedTable::Get. (To trace the referenced key and whether the
// referenced key exists in a fetched data block.)
// 5. BlockBasedTable::MultiGet. (To trace the referenced key and whether the
// referenced key exists in a fetched data block.)
// The context is created at:
// 1. BlockBasedTable::Get. (kUserGet)
// 2. BlockBasedTable::MultiGet. (kUserMGet)
// 3. BlockBasedTable::NewIterator. (either kUserIterator, kCompaction, or
// external SST ingestion calls this function.)
// 4. BlockBasedTable::Open. (kPrefetch)
// 5. Index/Filter::CacheDependencies. (kPrefetch)
// 6. BlockBasedTable::ApproximateOffsetOf. (kCompaction or
// kUserApproximateSize).
struct BlockCacheLookupContext {
BlockCacheLookupContext(const TableReaderCaller& _caller) : caller(_caller) {}
BlockCacheLookupContext(const TableReaderCaller& _caller, uint64_t _get_id,
bool _get_from_user_specified_snapshot)
: caller(_caller),
get_id(_get_id),
get_from_user_specified_snapshot(_get_from_user_specified_snapshot) {}
const TableReaderCaller caller;
// These are populated when we perform lookup/insert on block cache. The block
// cache tracer uses these inforation when logging the block access at
// BlockBasedTable::GET and BlockBasedTable::MultiGet.
bool is_cache_hit = false;
bool no_insert = false;
TraceType block_type = TraceType::kTraceMax;
uint64_t block_size = 0;
std::string block_key;
uint64_t num_keys_in_block = 0;
// The unique id associated with Get and MultiGet. This enables us to track
// how many blocks a Get/MultiGet request accesses. We can also measure the
// impact of row cache vs block cache.
uint64_t get_id = 0;
std::string referenced_key;
bool get_from_user_specified_snapshot = false;
void FillLookupContext(bool _is_cache_hit, bool _no_insert,
TraceType _block_type, uint64_t _block_size,
const std::string& _block_key,
uint64_t _num_keys_in_block) {
is_cache_hit = _is_cache_hit;
no_insert = _no_insert;
block_type = _block_type;
block_size = _block_size;
block_key = _block_key;
num_keys_in_block = _num_keys_in_block;
}
};
enum Boolean : char { kTrue = 1, kFalse = 0 };
struct BlockCacheTraceRecord {
// Required fields for all accesses.
uint64_t access_timestamp = 0;
std::string block_key;
TraceType block_type = TraceType::kTraceMax;
uint64_t block_size = 0;
uint64_t cf_id = 0;
std::string cf_name;
uint32_t level = 0;
uint64_t sst_fd_number = 0;
TableReaderCaller caller = TableReaderCaller::kMaxBlockCacheLookupCaller;
Boolean is_cache_hit = Boolean::kFalse;
Boolean no_insert = Boolean::kFalse;
// Required field for Get and MultiGet
uint64_t get_id = BlockCacheTraceHelper::kReservedGetId;
Boolean get_from_user_specified_snapshot = Boolean::kFalse;
std::string referenced_key;
// Required fields for data block and user Get/Multi-Get only.
uint64_t referenced_data_size = 0;
uint64_t num_keys_in_block = 0;
Boolean referenced_key_exist_in_block = Boolean::kFalse;
BlockCacheTraceRecord() {}
BlockCacheTraceRecord(
uint64_t _access_timestamp, std::string _block_key, TraceType _block_type,
uint64_t _block_size, uint64_t _cf_id, std::string _cf_name,
uint32_t _level, uint64_t _sst_fd_number, TableReaderCaller _caller,
bool _is_cache_hit, bool _no_insert,
uint64_t _get_id = BlockCacheTraceHelper::kReservedGetId,
bool _get_from_user_specified_snapshot = false,
std::string _referenced_key = "", uint64_t _referenced_data_size = 0,
uint64_t _num_keys_in_block = 0,
bool _referenced_key_exist_in_block = false)
: access_timestamp(_access_timestamp),
block_key(_block_key),
block_type(_block_type),
block_size(_block_size),
cf_id(_cf_id),
cf_name(_cf_name),
level(_level),
sst_fd_number(_sst_fd_number),
caller(_caller),
is_cache_hit(_is_cache_hit ? Boolean::kTrue : Boolean::kFalse),
no_insert(_no_insert ? Boolean::kTrue : Boolean::kFalse),
get_id(_get_id),
get_from_user_specified_snapshot(_get_from_user_specified_snapshot
? Boolean::kTrue
: Boolean::kFalse),
referenced_key(_referenced_key),
referenced_data_size(_referenced_data_size),
num_keys_in_block(_num_keys_in_block),
referenced_key_exist_in_block(
_referenced_key_exist_in_block ? Boolean::kTrue : Boolean::kFalse) {
}
};
struct BlockCacheTraceHeader {
uint64_t start_time;
uint32_t rocksdb_major_version;
uint32_t rocksdb_minor_version;
};
// BlockCacheTraceWriter captures all RocksDB block cache accesses using a
// user-provided TraceWriter. Every RocksDB operation is written as a single
// trace. Each trace will have a timestamp and type, followed by the trace
// payload.
class BlockCacheTraceWriter {
public:
BlockCacheTraceWriter(Env* env, const TraceOptions& trace_options,
std::unique_ptr<TraceWriter>&& trace_writer);
~BlockCacheTraceWriter() = default;
// No copy and move.
BlockCacheTraceWriter(const BlockCacheTraceWriter&) = delete;
BlockCacheTraceWriter& operator=(const BlockCacheTraceWriter&) = delete;
BlockCacheTraceWriter(BlockCacheTraceWriter&&) = delete;
BlockCacheTraceWriter& operator=(BlockCacheTraceWriter&&) = delete;
// Pass Slice references to avoid copy.
Status WriteBlockAccess(const BlockCacheTraceRecord& record,
const Slice& block_key, const Slice& cf_name,
const Slice& referenced_key);
// Write a trace header at the beginning, typically on initiating a trace,
// with some metadata like a magic number and RocksDB version.
Status WriteHeader();
private:
Env* env_;
TraceOptions trace_options_;
std::unique_ptr<TraceWriter> trace_writer_;
};
// BlockCacheTraceReader helps read the trace file generated by
// BlockCacheTraceWriter using a user provided TraceReader.
class BlockCacheTraceReader {
public:
BlockCacheTraceReader(std::unique_ptr<TraceReader>&& reader);
~BlockCacheTraceReader() = default;
// No copy and move.
BlockCacheTraceReader(const BlockCacheTraceReader&) = delete;
BlockCacheTraceReader& operator=(const BlockCacheTraceReader&) = delete;
BlockCacheTraceReader(BlockCacheTraceReader&&) = delete;
BlockCacheTraceReader& operator=(BlockCacheTraceReader&&) = delete;
Status ReadHeader(BlockCacheTraceHeader* header);
Status ReadAccess(BlockCacheTraceRecord* record);
private:
std::unique_ptr<TraceReader> trace_reader_;
};
// A block cache tracer. It downsamples the accesses according to
// trace_options and uses BlockCacheTraceWriter to write the access record to
// the trace file.
class BlockCacheTracer {
public:
BlockCacheTracer();
~BlockCacheTracer();
// No copy and move.
BlockCacheTracer(const BlockCacheTracer&) = delete;
BlockCacheTracer& operator=(const BlockCacheTracer&) = delete;
BlockCacheTracer(BlockCacheTracer&&) = delete;
BlockCacheTracer& operator=(BlockCacheTracer&&) = delete;
// Start writing block cache accesses to the trace_writer.
Status StartTrace(Env* env, const TraceOptions& trace_options,
std::unique_ptr<TraceWriter>&& trace_writer);
// Stop writing block cache accesses to the trace_writer.
void EndTrace();
bool is_tracing_enabled() const {
return writer_.load(std::memory_order_relaxed);
}
Status WriteBlockAccess(const BlockCacheTraceRecord& record,
const Slice& block_key, const Slice& cf_name,
const Slice& referenced_key);
// GetId cycles from 1 to port::kMaxUint64.
uint64_t NextGetId();
private:
TraceOptions trace_options_;
// A mutex protects the writer_.
InstrumentedMutex trace_writer_mutex_;
std::atomic<BlockCacheTraceWriter*> writer_;
std::atomic<uint64_t> get_id_counter_;
};
} // namespace rocksdb