rocksdb/trace_replay/block_cache_tracer.cc
haoyuhuang 6edc5d0719 Block cache tracing: Associate a unique id with Get and MultiGet (#5514)
Summary:
This PR associates a unique id 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.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5514

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

Differential Revision: D16032681

Pulled By: HaoyuHuang

fbshipit-source-id: 775b05f4440badd58de6667e3ec9f4fc87a0af4c
2019-07-03 19:35:41 -07:00

297 lines
10 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).
#include "trace_replay/block_cache_tracer.h"
#include "db/db_impl/db_impl.h"
#include "rocksdb/slice.h"
#include "util/coding.h"
#include "util/hash.h"
#include "util/string_util.h"
namespace rocksdb {
namespace {
const unsigned int kCharSize = 1;
bool ShouldTrace(const Slice& block_key, const TraceOptions& trace_options) {
if (trace_options.sampling_frequency == 0 ||
trace_options.sampling_frequency == 1) {
return true;
}
// We use spatial downsampling so that we have a complete access history for a
// block.
const uint64_t hash = GetSliceNPHash64(block_key);
return hash % trace_options.sampling_frequency == 0;
}
} // namespace
const uint64_t kMicrosInSecond = 1000 * 1000;
const std::string BlockCacheTraceHelper::kUnknownColumnFamilyName =
"UnknownColumnFamily";
const uint64_t BlockCacheTraceHelper::kReservedGetId = 0;
bool BlockCacheTraceHelper::ShouldTraceReferencedKey(TraceType block_type,
TableReaderCaller caller) {
return (block_type == TraceType::kBlockTraceDataBlock) &&
(caller == TableReaderCaller::kUserGet ||
caller == TableReaderCaller::kUserMultiGet);
}
bool BlockCacheTraceHelper::ShouldTraceGetId(TableReaderCaller caller) {
return caller == TableReaderCaller::kUserGet ||
caller == TableReaderCaller::kUserMultiGet;
}
BlockCacheTraceWriter::BlockCacheTraceWriter(
Env* env, const TraceOptions& trace_options,
std::unique_ptr<TraceWriter>&& trace_writer)
: env_(env),
trace_options_(trace_options),
trace_writer_(std::move(trace_writer)) {}
Status BlockCacheTraceWriter::WriteBlockAccess(
const BlockCacheTraceRecord& record, const Slice& block_key,
const Slice& cf_name, const Slice& referenced_key) {
uint64_t trace_file_size = trace_writer_->GetFileSize();
if (trace_file_size > trace_options_.max_trace_file_size) {
return Status::OK();
}
Trace trace;
trace.ts = record.access_timestamp;
trace.type = record.block_type;
PutLengthPrefixedSlice(&trace.payload, block_key);
PutFixed64(&trace.payload, record.block_size);
PutFixed64(&trace.payload, record.cf_id);
PutLengthPrefixedSlice(&trace.payload, cf_name);
PutFixed32(&trace.payload, record.level);
PutFixed64(&trace.payload, record.sst_fd_number);
trace.payload.push_back(record.caller);
trace.payload.push_back(record.is_cache_hit);
trace.payload.push_back(record.no_insert);
if (BlockCacheTraceHelper::ShouldTraceGetId(record.caller)) {
PutFixed64(&trace.payload, record.get_id);
}
if (BlockCacheTraceHelper::ShouldTraceReferencedKey(record.block_type,
record.caller)) {
PutLengthPrefixedSlice(&trace.payload, referenced_key);
PutFixed64(&trace.payload, record.referenced_data_size);
PutFixed64(&trace.payload, record.num_keys_in_block);
trace.payload.push_back(record.referenced_key_exist_in_block);
}
std::string encoded_trace;
TracerHelper::EncodeTrace(trace, &encoded_trace);
return trace_writer_->Write(encoded_trace);
}
Status BlockCacheTraceWriter::WriteHeader() {
Trace trace;
trace.ts = env_->NowMicros();
trace.type = TraceType::kTraceBegin;
PutLengthPrefixedSlice(&trace.payload, kTraceMagic);
PutFixed32(&trace.payload, kMajorVersion);
PutFixed32(&trace.payload, kMinorVersion);
std::string encoded_trace;
TracerHelper::EncodeTrace(trace, &encoded_trace);
return trace_writer_->Write(encoded_trace);
}
BlockCacheTraceReader::BlockCacheTraceReader(
std::unique_ptr<TraceReader>&& reader)
: trace_reader_(std::move(reader)) {}
Status BlockCacheTraceReader::ReadHeader(BlockCacheTraceHeader* header) {
assert(header != nullptr);
std::string encoded_trace;
Status s = trace_reader_->Read(&encoded_trace);
if (!s.ok()) {
return s;
}
Trace trace;
s = TracerHelper::DecodeTrace(encoded_trace, &trace);
if (!s.ok()) {
return s;
}
header->start_time = trace.ts;
Slice enc_slice = Slice(trace.payload);
Slice magnic_number;
if (!GetLengthPrefixedSlice(&enc_slice, &magnic_number)) {
return Status::Corruption(
"Corrupted header in the trace file: Failed to read the magic number.");
}
if (magnic_number.ToString() != kTraceMagic) {
return Status::Corruption(
"Corrupted header in the trace file: Magic number does not match.");
}
if (!GetFixed32(&enc_slice, &header->rocksdb_major_version)) {
return Status::Corruption(
"Corrupted header in the trace file: Failed to read rocksdb major "
"version number.");
}
if (!GetFixed32(&enc_slice, &header->rocksdb_minor_version)) {
return Status::Corruption(
"Corrupted header in the trace file: Failed to read rocksdb minor "
"version number.");
}
// We should have retrieved all information in the header.
if (!enc_slice.empty()) {
return Status::Corruption(
"Corrupted header in the trace file: The length of header is too "
"long.");
}
return Status::OK();
}
Status BlockCacheTraceReader::ReadAccess(BlockCacheTraceRecord* record) {
assert(record);
std::string encoded_trace;
Status s = trace_reader_->Read(&encoded_trace);
if (!s.ok()) {
return s;
}
Trace trace;
s = TracerHelper::DecodeTrace(encoded_trace, &trace);
if (!s.ok()) {
return s;
}
record->access_timestamp = trace.ts;
record->block_type = trace.type;
Slice enc_slice = Slice(trace.payload);
Slice block_key;
if (!GetLengthPrefixedSlice(&enc_slice, &block_key)) {
return Status::Incomplete(
"Incomplete access record: Failed to read block key.");
}
record->block_key = block_key.ToString();
if (!GetFixed64(&enc_slice, &record->block_size)) {
return Status::Incomplete(
"Incomplete access record: Failed to read block size.");
}
if (!GetFixed64(&enc_slice, &record->cf_id)) {
return Status::Incomplete(
"Incomplete access record: Failed to read column family ID.");
}
Slice cf_name;
if (!GetLengthPrefixedSlice(&enc_slice, &cf_name)) {
return Status::Incomplete(
"Incomplete access record: Failed to read column family name.");
}
record->cf_name = cf_name.ToString();
if (!GetFixed32(&enc_slice, &record->level)) {
return Status::Incomplete(
"Incomplete access record: Failed to read level.");
}
if (!GetFixed64(&enc_slice, &record->sst_fd_number)) {
return Status::Incomplete(
"Incomplete access record: Failed to read SST file number.");
}
if (enc_slice.empty()) {
return Status::Incomplete(
"Incomplete access record: Failed to read caller.");
}
record->caller = static_cast<TableReaderCaller>(enc_slice[0]);
enc_slice.remove_prefix(kCharSize);
if (enc_slice.empty()) {
return Status::Incomplete(
"Incomplete access record: Failed to read is_cache_hit.");
}
record->is_cache_hit = static_cast<Boolean>(enc_slice[0]);
enc_slice.remove_prefix(kCharSize);
if (enc_slice.empty()) {
return Status::Incomplete(
"Incomplete access record: Failed to read no_insert.");
}
record->no_insert = static_cast<Boolean>(enc_slice[0]);
enc_slice.remove_prefix(kCharSize);
if (BlockCacheTraceHelper::ShouldTraceGetId(record->caller)) {
if (!GetFixed64(&enc_slice, &record->get_id)) {
return Status::Incomplete(
"Incomplete access record: Failed to read the get id.");
}
}
if (BlockCacheTraceHelper::ShouldTraceReferencedKey(record->block_type,
record->caller)) {
Slice referenced_key;
if (!GetLengthPrefixedSlice(&enc_slice, &referenced_key)) {
return Status::Incomplete(
"Incomplete access record: Failed to read the referenced key.");
}
record->referenced_key = referenced_key.ToString();
if (!GetFixed64(&enc_slice, &record->referenced_data_size)) {
return Status::Incomplete(
"Incomplete access record: Failed to read the referenced data size.");
}
if (!GetFixed64(&enc_slice, &record->num_keys_in_block)) {
return Status::Incomplete(
"Incomplete access record: Failed to read the number of keys in the "
"block.");
}
if (enc_slice.empty()) {
return Status::Incomplete(
"Incomplete access record: Failed to read "
"referenced_key_exist_in_block.");
}
record->referenced_key_exist_in_block = static_cast<Boolean>(enc_slice[0]);
}
return Status::OK();
}
BlockCacheTracer::BlockCacheTracer() { writer_.store(nullptr); }
BlockCacheTracer::~BlockCacheTracer() { EndTrace(); }
Status BlockCacheTracer::StartTrace(
Env* env, const TraceOptions& trace_options,
std::unique_ptr<TraceWriter>&& trace_writer) {
InstrumentedMutexLock lock_guard(&trace_writer_mutex_);
if (writer_.load()) {
return Status::Busy();
}
get_id_counter_.store(1);
trace_options_ = trace_options;
writer_.store(
new BlockCacheTraceWriter(env, trace_options, std::move(trace_writer)));
return writer_.load()->WriteHeader();
}
void BlockCacheTracer::EndTrace() {
InstrumentedMutexLock lock_guard(&trace_writer_mutex_);
if (!writer_.load()) {
return;
}
delete writer_.load();
writer_.store(nullptr);
}
Status BlockCacheTracer::WriteBlockAccess(const BlockCacheTraceRecord& record,
const Slice& block_key,
const Slice& cf_name,
const Slice& referenced_key) {
if (!writer_.load() || !ShouldTrace(block_key, trace_options_)) {
return Status::OK();
}
InstrumentedMutexLock lock_guard(&trace_writer_mutex_);
if (!writer_.load()) {
return Status::OK();
}
return writer_.load()->WriteBlockAccess(record, block_key, cf_name,
referenced_key);
}
uint64_t BlockCacheTracer::NextGetId() {
if (!writer_.load(std::memory_order_relaxed)) {
return BlockCacheTraceHelper::kReservedGetId;
}
uint64_t prev_value = get_id_counter_.fetch_add(1);
if (prev_value == BlockCacheTraceHelper::kReservedGetId) {
// fetch and add again.
return get_id_counter_.fetch_add(1);
}
return prev_value;
}
} // namespace rocksdb