Revision 499ebb3ab5ea4207950fc95acf102b8f58add1c5 authored by Maysam Yabandeh on 24 June 2017, 21:06:43 UTC, committed by Facebook Github Bot on 24 June 2017, 21:11:29 UTC
Summary: Throughput: 46k tps in our sysbench settings (filling the details later) The idea is to have the simplest change that gives us a reasonable boost in 2PC throughput. Major design changes: 1. The WAL file internal buffer is not flushed after each write. Instead it is flushed before critical operations (WAL copy via fs) or when FlushWAL is called by MySQL. Flushing the WAL buffer is also protected via mutex_. 2. Use two sequence numbers: last seq, and last seq for write. Last seq is the last visible sequence number for reads. Last seq for write is the next sequence number that should be used to write to WAL/memtable. This allows to have a memtable write be in parallel to WAL writes. 3. BatchGroup is not used for writes. This means that we can have parallel writers which changes a major assumption in the code base. To accommodate for that i) allow only 1 WriteImpl that intends to write to memtable via mem_mutex_--which is fine since in 2PC almost all of the memtable writes come via group commit phase which is serial anyway, ii) make all the parts in the code base that assumed to be the only writer (via EnterUnbatched) to also acquire mem_mutex_, iii) stat updates are protected via a stat_mutex_. Note: the first commit has the approach figured out but is not clean. Submitting the PR anyway to get the early feedback on the approach. If we are ok with the approach I will go ahead with this updates: 0) Rebase with Yi's pipelining changes 1) Currently batching is disabled by default to make sure that it will be consistent with all unit tests. Will make this optional via a config. 2) A couple of unit tests are disabled. They need to be updated with the serial commit of 2PC taken into account. 3) Replacing BatchGroup with mem_mutex_ got a bit ugly as it requires releasing mutex_ beforehand (the same way EnterUnbatched does). This needs to be cleaned up. Closes https://github.com/facebook/rocksdb/pull/2345 Differential Revision: D5210732 Pulled By: maysamyabandeh fbshipit-source-id: 78653bd95a35cd1e831e555e0e57bdfd695355a4
1 parent 0ac4afb
sync_point.h
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
// This source code is also licensed under the GPLv2 license found in the
// COPYING file in the root directory of this source tree.
#pragma once
#include <assert.h>
#include <condition_variable>
#include <functional>
#include <mutex>
#include <string>
#include <thread>
#include <unordered_map>
#include <unordered_set>
#include <vector>
// This is only set from db_stress.cc and for testing only.
// If non-zero, kill at various points in source code with probability 1/this
extern int rocksdb_kill_odds;
// If kill point has a prefix on this list, will skip killing.
extern std::vector<std::string> rocksdb_kill_prefix_blacklist;
#ifdef NDEBUG
// empty in release build
#define TEST_KILL_RANDOM(kill_point, rocksdb_kill_odds)
#else
namespace rocksdb {
// Kill the process with probablity 1/odds for testing.
extern void TestKillRandom(std::string kill_point, int odds,
const std::string& srcfile, int srcline);
// To avoid crashing always at some frequently executed codepaths (during
// kill random test), use this factor to reduce odds
#define REDUCE_ODDS 2
#define REDUCE_ODDS2 4
#define TEST_KILL_RANDOM(kill_point, rocksdb_kill_odds) \
{ \
if (rocksdb_kill_odds > 0) { \
TestKillRandom(kill_point, rocksdb_kill_odds, __FILE__, __LINE__); \
} \
}
} // namespace rocksdb
#endif
#ifdef NDEBUG
#define TEST_SYNC_POINT(x)
#define TEST_SYNC_POINT_CALLBACK(x, y)
#else
namespace rocksdb {
// This class provides facility to reproduce race conditions deterministically
// in unit tests.
// Developer could specify sync points in the codebase via TEST_SYNC_POINT.
// Each sync point represents a position in the execution stream of a thread.
// In the unit test, 'Happens After' relationship among sync points could be
// setup via SyncPoint::LoadDependency, to reproduce a desired interleave of
// threads execution.
// Refer to (DBTest,TransactionLogIteratorRace), for an example use case.
class SyncPoint {
public:
static SyncPoint* GetInstance();
struct SyncPointPair {
std::string predecessor;
std::string successor;
};
// call once at the beginning of a test to setup the dependency between
// sync points
void LoadDependency(const std::vector<SyncPointPair>& dependencies);
// call once at the beginning of a test to setup the dependency between
// sync points and setup markers indicating the successor is only enabled
// when it is processed on the same thread as the predecessor.
// When adding a marker, it implicitly adds a dependency for the marker pair.
void LoadDependencyAndMarkers(const std::vector<SyncPointPair>& dependencies,
const std::vector<SyncPointPair>& markers);
// Set up a call back function in sync point.
void SetCallBack(const std::string point,
std::function<void(void*)> callback);
// Clear callback function by point
void ClearCallBack(const std::string point);
// Clear all call back functions.
void ClearAllCallBacks();
// enable sync point processing (disabled on startup)
void EnableProcessing();
// disable sync point processing
void DisableProcessing();
// remove the execution trace of all sync points
void ClearTrace();
// triggered by TEST_SYNC_POINT, blocking execution until all predecessors
// are executed.
// And/or call registered callback functionn, with argument `cb_arg`
void Process(const std::string& point, void* cb_arg = nullptr);
// TODO: it might be useful to provide a function that blocks until all
// sync points are cleared.
private:
bool PredecessorsAllCleared(const std::string& point);
bool DisabledByMarker(const std::string& point, std::thread::id thread_id);
// successor/predecessor map loaded from LoadDependency
std::unordered_map<std::string, std::vector<std::string>> successors_;
std::unordered_map<std::string, std::vector<std::string>> predecessors_;
std::unordered_map<std::string, std::function<void(void*)> > callbacks_;
std::unordered_map<std::string, std::vector<std::string> > markers_;
std::unordered_map<std::string, std::thread::id> marked_thread_id_;
std::mutex mutex_;
std::condition_variable cv_;
// sync points that have been passed through
std::unordered_set<std::string> cleared_points_;
bool enabled_ = false;
int num_callbacks_running_ = 0;
};
} // namespace rocksdb
// Use TEST_SYNC_POINT to specify sync points inside code base.
// Sync points can have happens-after depedency on other sync points,
// configured at runtime via SyncPoint::LoadDependency. This could be
// utilized to re-produce race conditions between threads.
// See TransactionLogIteratorRace in db_test.cc for an example use case.
// TEST_SYNC_POINT is no op in release build.
#define TEST_SYNC_POINT(x) rocksdb::SyncPoint::GetInstance()->Process(x)
#define TEST_SYNC_POINT_CALLBACK(x, y) \
rocksdb::SyncPoint::GetInstance()->Process(x, y)
#endif // NDEBUG
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