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c3105aa50d
rocksdb/db/db_impl_write.cc
Yanqin Jin 92b4401566 Avoid memtable cut when active memtable is empty (#4595) 
Summary:
For flush triggered by RocksDB due to memory usage approaching certain
threshold (WriteBufferManager or Memtable full), we should cut the memtable
only when the current active memtable is not empty, i.e. contains data. This is
what we do for non-atomic flush. If we always cut memtable even when the active
memtable is empty, we will generate extra, empty immutable memtable.
This is not ideal since it may cause write stall. It also causes some
DBAtomicFlushTest to fail because cfd->imm()->NumNotFlushed() is different from
expectation.

Test plan
```
$make clean && make J=1 -j32 all check
$make clean && OPT="-DROCKSDB_LITE -g" make J=1 -j32 all check
$make clean && TEST_TMPDIR=/dev/shm/rocksdb OPT=-g make J=1 -j32 valgrind_test
```
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4595

Differential Revision: D12818520

Pulled By: riversand963

fbshipit-source-id: d867bdbeacf4199fdd642debb085f94703c41a18
2018-10-29 09:45:32 -07:00

1614 lines
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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/db_impl.h"
#ifndef __STDC_FORMAT_MACROS
#define __STDC_FORMAT_MACROS
#endif
#include <inttypes.h>
#include "db/error_handler.h"
#include "db/event_helpers.h"
#include "monitoring/perf_context_imp.h"
#include "options/options_helper.h"
#include "util/sync_point.h"
namespace rocksdb {
// Convenience methods
Status DBImpl::Put(const WriteOptions& o, ColumnFamilyHandle* column_family,
const Slice& key, const Slice& val) {
return DB::Put(o, column_family, key, val);
}
Status DBImpl::Merge(const WriteOptions& o, ColumnFamilyHandle* column_family,
const Slice& key, const Slice& val) {
auto cfh = reinterpret_cast<ColumnFamilyHandleImpl*>(column_family);
if (!cfh->cfd()->ioptions()->merge_operator) {
return Status::NotSupported("Provide a merge_operator when opening DB");
} else {
return DB::Merge(o, column_family, key, val);
}
}
Status DBImpl::Delete(const WriteOptions& write_options,
ColumnFamilyHandle* column_family, const Slice& key) {
return DB::Delete(write_options, column_family, key);
}
Status DBImpl::SingleDelete(const WriteOptions& write_options,
ColumnFamilyHandle* column_family,
const Slice& key) {
return DB::SingleDelete(write_options, column_family, key);
}
void DBImpl::SetRecoverableStatePreReleaseCallback(
PreReleaseCallback* callback) {
recoverable_state_pre_release_callback_.reset(callback);
}
Status DBImpl::Write(const WriteOptions& write_options, WriteBatch* my_batch) {
return WriteImpl(write_options, my_batch, nullptr, nullptr);
}
#ifndef ROCKSDB_LITE
Status DBImpl::WriteWithCallback(const WriteOptions& write_options,
WriteBatch* my_batch,
WriteCallback* callback) {
return WriteImpl(write_options, my_batch, callback, nullptr);
}
#endif // ROCKSDB_LITE
// The main write queue. This is the only write queue that updates LastSequence.
// When using one write queue, the same sequence also indicates the last
// published sequence.
Status DBImpl::WriteImpl(const WriteOptions& write_options,
WriteBatch* my_batch, WriteCallback* callback,
uint64_t* log_used, uint64_t log_ref,
bool disable_memtable, uint64_t* seq_used,
size_t batch_cnt,
PreReleaseCallback* pre_release_callback) {
assert(!seq_per_batch_ || batch_cnt != 0);
if (my_batch == nullptr) {
return Status::Corruption("Batch is nullptr!");
}
if (tracer_) {
InstrumentedMutexLock lock(&trace_mutex_);
if (tracer_) {
tracer_->Write(my_batch);
}
}
if (write_options.sync && write_options.disableWAL) {
return Status::InvalidArgument("Sync writes has to enable WAL.");
}
if (two_write_queues_ && immutable_db_options_.enable_pipelined_write) {
return Status::NotSupported(
"pipelined_writes is not compatible with concurrent prepares");
}
if (seq_per_batch_ && immutable_db_options_.enable_pipelined_write) {
// TODO(yiwu): update pipeline write with seq_per_batch and batch_cnt
return Status::NotSupported(
"pipelined_writes is not compatible with seq_per_batch");
}
// Otherwise IsLatestPersistentState optimization does not make sense
assert(!WriteBatchInternal::IsLatestPersistentState(my_batch) ||
disable_memtable);
Status status;
if (write_options.low_pri) {
status = ThrottleLowPriWritesIfNeeded(write_options, my_batch);
if (!status.ok()) {
return status;
}
}
if (two_write_queues_ && disable_memtable) {
return WriteImplWALOnly(write_options, my_batch, callback, log_used,
log_ref, seq_used, batch_cnt, pre_release_callback);
}
if (immutable_db_options_.enable_pipelined_write) {
return PipelinedWriteImpl(write_options, my_batch, callback, log_used,
log_ref, disable_memtable, seq_used);
}
PERF_TIMER_GUARD(write_pre_and_post_process_time);
WriteThread::Writer w(write_options, my_batch, callback, log_ref,
disable_memtable, batch_cnt, pre_release_callback);
if (!write_options.disableWAL) {
RecordTick(stats_, WRITE_WITH_WAL);
}
StopWatch write_sw(env_, immutable_db_options_.statistics.get(), DB_WRITE);
write_thread_.JoinBatchGroup(&w);
if (w.state == WriteThread::STATE_PARALLEL_MEMTABLE_WRITER) {
// we are a non-leader in a parallel group
if (w.ShouldWriteToMemtable()) {
PERF_TIMER_STOP(write_pre_and_post_process_time);
PERF_TIMER_GUARD(write_memtable_time);
ColumnFamilyMemTablesImpl column_family_memtables(
versions_->GetColumnFamilySet());
w.status = WriteBatchInternal::InsertInto(
&w, w.sequence, &column_family_memtables, &flush_scheduler_,
write_options.ignore_missing_column_families, 0 /*log_number*/, this,
true /*concurrent_memtable_writes*/, seq_per_batch_, w.batch_cnt);
PERF_TIMER_START(write_pre_and_post_process_time);
}
if (write_thread_.CompleteParallelMemTableWriter(&w)) {
// we're responsible for exit batch group
for (auto* writer : *(w.write_group)) {
if (!writer->CallbackFailed() && writer->pre_release_callback) {
assert(writer->sequence != kMaxSequenceNumber);
Status ws = writer->pre_release_callback->Callback(writer->sequence,
disable_memtable);
if (!ws.ok()) {
status = ws;
break;
}
}
}
// TODO(myabandeh): propagate status to write_group
auto last_sequence = w.write_group->last_sequence;
versions_->SetLastSequence(last_sequence);
MemTableInsertStatusCheck(w.status);
write_thread_.ExitAsBatchGroupFollower(&w);
}
assert(w.state == WriteThread::STATE_COMPLETED);
// STATE_COMPLETED conditional below handles exit
status = w.FinalStatus();
}
if (w.state == WriteThread::STATE_COMPLETED) {
if (log_used != nullptr) {
*log_used = w.log_used;
}
if (seq_used != nullptr) {
*seq_used = w.sequence;
}
// write is complete and leader has updated sequence
return w.FinalStatus();
}
// else we are the leader of the write batch group
assert(w.state == WriteThread::STATE_GROUP_LEADER);
// Once reaches this point, the current writer "w" will try to do its write
// job. It may also pick up some of the remaining writers in the "writers_"
// when it finds suitable, and finish them in the same write batch.
// This is how a write job could be done by the other writer.
WriteContext write_context;
WriteThread::WriteGroup write_group;
bool in_parallel_group = false;
uint64_t last_sequence = kMaxSequenceNumber;
if (!two_write_queues_) {
last_sequence = versions_->LastSequence();
}
mutex_.Lock();
bool need_log_sync = write_options.sync;
bool need_log_dir_sync = need_log_sync && !log_dir_synced_;
if (!two_write_queues_ || !disable_memtable) {
// With concurrent writes we do preprocess only in the write thread that
// also does write to memtable to avoid sync issue on shared data structure
// with the other thread
// PreprocessWrite does its own perf timing.
PERF_TIMER_STOP(write_pre_and_post_process_time);
status = PreprocessWrite(write_options, &need_log_sync, &write_context);
PERF_TIMER_START(write_pre_and_post_process_time);
}
log::Writer* log_writer = logs_.back().writer;
mutex_.Unlock();
// Add to log and apply to memtable. We can release the lock
// during this phase since &w is currently responsible for logging
// and protects against concurrent loggers and concurrent writes
// into memtables
TEST_SYNC_POINT("DBImpl::WriteImpl:BeforeLeaderEnters");
last_batch_group_size_ =
write_thread_.EnterAsBatchGroupLeader(&w, &write_group);
if (status.ok()) {
// Rules for when we can update the memtable concurrently
// 1. supported by memtable
// 2. Puts are not okay if inplace_update_support
// 3. Merges are not okay
//
// Rules 1..2 are enforced by checking the options
// during startup (CheckConcurrentWritesSupported), so if
// options.allow_concurrent_memtable_write is true then they can be
// assumed to be true. Rule 3 is checked for each batch. We could
// relax rules 2 if we could prevent write batches from referring
// more than once to a particular key.
bool parallel = immutable_db_options_.allow_concurrent_memtable_write &&
write_group.size > 1;
size_t total_count = 0;
size_t valid_batches = 0;
size_t total_byte_size = 0;
for (auto* writer : write_group) {
if (writer->CheckCallback(this)) {
valid_batches += writer->batch_cnt;
if (writer->ShouldWriteToMemtable()) {
total_count += WriteBatchInternal::Count(writer->batch);
parallel = parallel && !writer->batch->HasMerge();
}
total_byte_size = WriteBatchInternal::AppendedByteSize(
total_byte_size, WriteBatchInternal::ByteSize(writer->batch));
}
}
// Note about seq_per_batch_: either disableWAL is set for the entire write
// group or not. In either case we inc seq for each write batch with no
// failed callback. This means that there could be a batch with
// disalbe_memtable in between; although we do not write this batch to
// memtable it still consumes a seq. Otherwise, if !seq_per_batch_, we inc
// the seq per valid written key to mem.
size_t seq_inc = seq_per_batch_ ? valid_batches : total_count;
const bool concurrent_update = two_write_queues_;
// Update stats while we are an exclusive group leader, so we know
// that nobody else can be writing to these particular stats.
// We're optimistic, updating the stats before we successfully
// commit. That lets us release our leader status early.
auto stats = default_cf_internal_stats_;
stats->AddDBStats(InternalStats::NUMBER_KEYS_WRITTEN, total_count,
concurrent_update);
RecordTick(stats_, NUMBER_KEYS_WRITTEN, total_count);
stats->AddDBStats(InternalStats::BYTES_WRITTEN, total_byte_size,
concurrent_update);
RecordTick(stats_, BYTES_WRITTEN, total_byte_size);
stats->AddDBStats(InternalStats::WRITE_DONE_BY_SELF, 1, concurrent_update);
RecordTick(stats_, WRITE_DONE_BY_SELF);
auto write_done_by_other = write_group.size - 1;
if (write_done_by_other > 0) {
stats->AddDBStats(InternalStats::WRITE_DONE_BY_OTHER, write_done_by_other,
concurrent_update);
RecordTick(stats_, WRITE_DONE_BY_OTHER, write_done_by_other);
}
MeasureTime(stats_, BYTES_PER_WRITE, total_byte_size);
if (write_options.disableWAL) {
has_unpersisted_data_.store(true, std::memory_order_relaxed);
}
PERF_TIMER_STOP(write_pre_and_post_process_time);
if (!two_write_queues_) {
if (status.ok() && !write_options.disableWAL) {
PERF_TIMER_GUARD(write_wal_time);
status = WriteToWAL(write_group, log_writer, log_used, need_log_sync,
need_log_dir_sync, last_sequence + 1);
}
} else {
if (status.ok() && !write_options.disableWAL) {
PERF_TIMER_GUARD(write_wal_time);
// LastAllocatedSequence is increased inside WriteToWAL under
// wal_write_mutex_ to ensure ordered events in WAL
status = ConcurrentWriteToWAL(write_group, log_used, &last_sequence,
seq_inc);
} else {
// Otherwise we inc seq number for memtable writes
last_sequence = versions_->FetchAddLastAllocatedSequence(seq_inc);
}
}
assert(last_sequence != kMaxSequenceNumber);
const SequenceNumber current_sequence = last_sequence + 1;
last_sequence += seq_inc;
if (status.ok()) {
PERF_TIMER_GUARD(write_memtable_time);
if (!parallel) {
// w.sequence will be set inside InsertInto
w.status = WriteBatchInternal::InsertInto(
write_group, current_sequence, column_family_memtables_.get(),
&flush_scheduler_, write_options.ignore_missing_column_families,
0 /*recovery_log_number*/, this, parallel, seq_per_batch_,
batch_per_txn_);
} else {
SequenceNumber next_sequence = current_sequence;
// Note: the logic for advancing seq here must be consistent with the
// logic in WriteBatchInternal::InsertInto(write_group...) as well as
// with WriteBatchInternal::InsertInto(write_batch...) that is called on
// the merged batch during recovery from the WAL.
for (auto* writer : write_group) {
if (writer->CallbackFailed()) {
continue;
}
writer->sequence = next_sequence;
if (seq_per_batch_) {
assert(writer->batch_cnt);
next_sequence += writer->batch_cnt;
} else if (writer->ShouldWriteToMemtable()) {
next_sequence += WriteBatchInternal::Count(writer->batch);
}
}
write_group.last_sequence = last_sequence;
write_thread_.LaunchParallelMemTableWriters(&write_group);
in_parallel_group = true;
// Each parallel follower is doing each own writes. The leader should
// also do its own.
if (w.ShouldWriteToMemtable()) {
ColumnFamilyMemTablesImpl column_family_memtables(
versions_->GetColumnFamilySet());
assert(w.sequence == current_sequence);
w.status = WriteBatchInternal::InsertInto(
&w, w.sequence, &column_family_memtables, &flush_scheduler_,
write_options.ignore_missing_column_families, 0 /*log_number*/,
this, true /*concurrent_memtable_writes*/, seq_per_batch_,
w.batch_cnt, batch_per_txn_);
}
}
if (seq_used != nullptr) {
*seq_used = w.sequence;
}
}
}
PERF_TIMER_START(write_pre_and_post_process_time);
if (!w.CallbackFailed()) {
WriteStatusCheck(status);
}
if (need_log_sync) {
mutex_.Lock();
MarkLogsSynced(logfile_number_, need_log_dir_sync, status);
mutex_.Unlock();
// Requesting sync with two_write_queues_ is expected to be very rare. We
// hence provide a simple implementation that is not necessarily efficient.
if (two_write_queues_) {
if (manual_wal_flush_) {
status = FlushWAL(true);
} else {
status = SyncWAL();
}
}
}
bool should_exit_batch_group = true;
if (in_parallel_group) {
// CompleteParallelWorker returns true if this thread should
// handle exit, false means somebody else did
should_exit_batch_group = write_thread_.CompleteParallelMemTableWriter(&w);
}
if (should_exit_batch_group) {
if (status.ok()) {
for (auto* writer : write_group) {
if (!writer->CallbackFailed() && writer->pre_release_callback) {
assert(writer->sequence != kMaxSequenceNumber);
Status ws = writer->pre_release_callback->Callback(writer->sequence,
disable_memtable);
if (!ws.ok()) {
status = ws;
break;
}
}
}
versions_->SetLastSequence(last_sequence);
}
MemTableInsertStatusCheck(w.status);
write_thread_.ExitAsBatchGroupLeader(write_group, status);
}
if (status.ok()) {
status = w.FinalStatus();
}
return status;
}
Status DBImpl::PipelinedWriteImpl(const WriteOptions& write_options,
WriteBatch* my_batch, WriteCallback* callback,
uint64_t* log_used, uint64_t log_ref,
bool disable_memtable, uint64_t* seq_used) {
PERF_TIMER_GUARD(write_pre_and_post_process_time);
StopWatch write_sw(env_, immutable_db_options_.statistics.get(), DB_WRITE);
WriteContext write_context;
WriteThread::Writer w(write_options, my_batch, callback, log_ref,
disable_memtable);
write_thread_.JoinBatchGroup(&w);
if (w.state == WriteThread::STATE_GROUP_LEADER) {
WriteThread::WriteGroup wal_write_group;
if (w.callback && !w.callback->AllowWriteBatching()) {
write_thread_.WaitForMemTableWriters();
}
mutex_.Lock();
bool need_log_sync = !write_options.disableWAL && write_options.sync;
bool need_log_dir_sync = need_log_sync && !log_dir_synced_;
// PreprocessWrite does its own perf timing.
PERF_TIMER_STOP(write_pre_and_post_process_time);
w.status = PreprocessWrite(write_options, &need_log_sync, &write_context);
PERF_TIMER_START(write_pre_and_post_process_time);
log::Writer* log_writer = logs_.back().writer;
mutex_.Unlock();
// This can set non-OK status if callback fail.
last_batch_group_size_ =
write_thread_.EnterAsBatchGroupLeader(&w, &wal_write_group);
const SequenceNumber current_sequence =
write_thread_.UpdateLastSequence(versions_->LastSequence()) + 1;
size_t total_count = 0;
size_t total_byte_size = 0;
if (w.status.ok()) {
SequenceNumber next_sequence = current_sequence;
for (auto writer : wal_write_group) {
if (writer->CheckCallback(this)) {
if (writer->ShouldWriteToMemtable()) {
writer->sequence = next_sequence;
size_t count = WriteBatchInternal::Count(writer->batch);
next_sequence += count;
total_count += count;
}
total_byte_size = WriteBatchInternal::AppendedByteSize(
total_byte_size, WriteBatchInternal::ByteSize(writer->batch));
}
}
if (w.disable_wal) {
has_unpersisted_data_.store(true, std::memory_order_relaxed);
}
write_thread_.UpdateLastSequence(current_sequence + total_count - 1);
}
auto stats = default_cf_internal_stats_;
stats->AddDBStats(InternalStats::NUMBER_KEYS_WRITTEN, total_count);
RecordTick(stats_, NUMBER_KEYS_WRITTEN, total_count);
stats->AddDBStats(InternalStats::BYTES_WRITTEN, total_byte_size);
RecordTick(stats_, BYTES_WRITTEN, total_byte_size);
MeasureTime(stats_, BYTES_PER_WRITE, total_byte_size);
PERF_TIMER_STOP(write_pre_and_post_process_time);
if (w.ShouldWriteToWAL()) {
PERF_TIMER_GUARD(write_wal_time);
stats->AddDBStats(InternalStats::WRITE_DONE_BY_SELF, 1);
RecordTick(stats_, WRITE_DONE_BY_SELF, 1);
if (wal_write_group.size > 1) {
stats->AddDBStats(InternalStats::WRITE_DONE_BY_OTHER,
wal_write_group.size - 1);
RecordTick(stats_, WRITE_DONE_BY_OTHER, wal_write_group.size - 1);
}
w.status = WriteToWAL(wal_write_group, log_writer, log_used,
need_log_sync, need_log_dir_sync, current_sequence);
}
if (!w.CallbackFailed()) {
WriteStatusCheck(w.status);
}
if (need_log_sync) {
mutex_.Lock();
MarkLogsSynced(logfile_number_, need_log_dir_sync, w.status);
mutex_.Unlock();
}
write_thread_.ExitAsBatchGroupLeader(wal_write_group, w.status);
}
WriteThread::WriteGroup memtable_write_group;
if (w.state == WriteThread::STATE_MEMTABLE_WRITER_LEADER) {
PERF_TIMER_GUARD(write_memtable_time);
assert(w.status.ok());
write_thread_.EnterAsMemTableWriter(&w, &memtable_write_group);
if (memtable_write_group.size > 1 &&
immutable_db_options_.allow_concurrent_memtable_write) {
write_thread_.LaunchParallelMemTableWriters(&memtable_write_group);
} else {
memtable_write_group.status = WriteBatchInternal::InsertInto(
memtable_write_group, w.sequence, column_family_memtables_.get(),
&flush_scheduler_, write_options.ignore_missing_column_families,
0 /*log_number*/, this, false /*concurrent_memtable_writes*/,
seq_per_batch_, batch_per_txn_);
versions_->SetLastSequence(memtable_write_group.last_sequence);
write_thread_.ExitAsMemTableWriter(&w, memtable_write_group);
}
}
if (w.state == WriteThread::STATE_PARALLEL_MEMTABLE_WRITER) {
assert(w.ShouldWriteToMemtable());
ColumnFamilyMemTablesImpl column_family_memtables(
versions_->GetColumnFamilySet());
w.status = WriteBatchInternal::InsertInto(
&w, w.sequence, &column_family_memtables, &flush_scheduler_,
write_options.ignore_missing_column_families, 0 /*log_number*/, this,
true /*concurrent_memtable_writes*/);
if (write_thread_.CompleteParallelMemTableWriter(&w)) {
MemTableInsertStatusCheck(w.status);
versions_->SetLastSequence(w.write_group->last_sequence);
write_thread_.ExitAsMemTableWriter(&w, *w.write_group);
}
}
if (seq_used != nullptr) {
*seq_used = w.sequence;
}
assert(w.state == WriteThread::STATE_COMPLETED);
return w.FinalStatus();
}
// The 2nd write queue. If enabled it will be used only for WAL-only writes.
// This is the only queue that updates LastPublishedSequence which is only
// applicable in a two-queue setting.
Status DBImpl::WriteImplWALOnly(const WriteOptions& write_options,
WriteBatch* my_batch, WriteCallback* callback,
uint64_t* log_used, uint64_t log_ref,
uint64_t* seq_used, size_t batch_cnt,
PreReleaseCallback* pre_release_callback) {
Status status;
PERF_TIMER_GUARD(write_pre_and_post_process_time);
WriteThread::Writer w(write_options, my_batch, callback, log_ref,
true /* disable_memtable */, batch_cnt,
pre_release_callback);
RecordTick(stats_, WRITE_WITH_WAL);
StopWatch write_sw(env_, immutable_db_options_.statistics.get(), DB_WRITE);
nonmem_write_thread_.JoinBatchGroup(&w);
assert(w.state != WriteThread::STATE_PARALLEL_MEMTABLE_WRITER);
if (w.state == WriteThread::STATE_COMPLETED) {
if (log_used != nullptr) {
*log_used = w.log_used;
}
if (seq_used != nullptr) {
*seq_used = w.sequence;
}
return w.FinalStatus();
}
// else we are the leader of the write batch group
assert(w.state == WriteThread::STATE_GROUP_LEADER);
WriteThread::WriteGroup write_group;
uint64_t last_sequence;
nonmem_write_thread_.EnterAsBatchGroupLeader(&w, &write_group);
// Note: no need to update last_batch_group_size_ here since the batch writes
// to WAL only
size_t total_byte_size = 0;
for (auto* writer : write_group) {
if (writer->CheckCallback(this)) {
total_byte_size = WriteBatchInternal::AppendedByteSize(
total_byte_size, WriteBatchInternal::ByteSize(writer->batch));
}
}
const bool concurrent_update = true;
// Update stats while we are an exclusive group leader, so we know
// that nobody else can be writing to these particular stats.
// We're optimistic, updating the stats before we successfully
// commit. That lets us release our leader status early.
auto stats = default_cf_internal_stats_;
stats->AddDBStats(InternalStats::BYTES_WRITTEN, total_byte_size,
concurrent_update);
RecordTick(stats_, BYTES_WRITTEN, total_byte_size);
stats->AddDBStats(InternalStats::WRITE_DONE_BY_SELF, 1, concurrent_update);
RecordTick(stats_, WRITE_DONE_BY_SELF);
auto write_done_by_other = write_group.size - 1;
if (write_done_by_other > 0) {
stats->AddDBStats(InternalStats::WRITE_DONE_BY_OTHER, write_done_by_other,
concurrent_update);
RecordTick(stats_, WRITE_DONE_BY_OTHER, write_done_by_other);
}
MeasureTime(stats_, BYTES_PER_WRITE, total_byte_size);
PERF_TIMER_STOP(write_pre_and_post_process_time);
PERF_TIMER_GUARD(write_wal_time);
// LastAllocatedSequence is increased inside WriteToWAL under
// wal_write_mutex_ to ensure ordered events in WAL
size_t seq_inc = 0 /* total_count */;
if (seq_per_batch_) {
size_t total_batch_cnt = 0;
for (auto* writer : write_group) {
assert(writer->batch_cnt);
total_batch_cnt += writer->batch_cnt;
}
seq_inc = total_batch_cnt;
}
if (!write_options.disableWAL) {
status =
ConcurrentWriteToWAL(write_group, log_used, &last_sequence, seq_inc);
} else {
// Otherwise we inc seq number to do solely the seq allocation
last_sequence = versions_->FetchAddLastAllocatedSequence(seq_inc);
}
auto curr_seq = last_sequence + 1;
for (auto* writer : write_group) {
if (writer->CallbackFailed()) {
continue;
}
writer->sequence = curr_seq;
if (seq_per_batch_) {
assert(writer->batch_cnt);
curr_seq += writer->batch_cnt;
}
// else seq advances only by memtable writes
}
if (status.ok() && write_options.sync) {
assert(!write_options.disableWAL);
// Requesting sync with two_write_queues_ is expected to be very rare. We
// hance provide a simple implementation that is not necessarily efficient.
if (manual_wal_flush_) {
status = FlushWAL(true);
} else {
status = SyncWAL();
}
}
PERF_TIMER_START(write_pre_and_post_process_time);
if (!w.CallbackFailed()) {
WriteStatusCheck(status);
}
if (status.ok()) {
for (auto* writer : write_group) {
if (!writer->CallbackFailed() && writer->pre_release_callback) {
assert(writer->sequence != kMaxSequenceNumber);
const bool DISABLE_MEMTABLE = true;
Status ws = writer->pre_release_callback->Callback(writer->sequence,
DISABLE_MEMTABLE);
if (!ws.ok()) {
status = ws;
break;
}
}
}
}
nonmem_write_thread_.ExitAsBatchGroupLeader(write_group, status);
if (status.ok()) {
status = w.FinalStatus();
}
if (seq_used != nullptr) {
*seq_used = w.sequence;
}
return status;
}
void DBImpl::WriteStatusCheck(const Status& status) {
// Is setting bg_error_ enough here? This will at least stop
// compaction and fail any further writes.
if (immutable_db_options_.paranoid_checks && !status.ok() &&
!status.IsBusy() && !status.IsIncomplete()) {
mutex_.Lock();
error_handler_.SetBGError(status, BackgroundErrorReason::kWriteCallback);
mutex_.Unlock();
}
}
void DBImpl::MemTableInsertStatusCheck(const Status& status) {
// A non-OK status here indicates that the state implied by the
// WAL has diverged from the in-memory state. This could be
// because of a corrupt write_batch (very bad), or because the
// client specified an invalid column family and didn't specify
// ignore_missing_column_families.
if (!status.ok()) {
mutex_.Lock();
assert(!error_handler_.IsBGWorkStopped());
error_handler_.SetBGError(status, BackgroundErrorReason::kMemTable);
mutex_.Unlock();
}
}
Status DBImpl::PreprocessWrite(const WriteOptions& write_options,
bool* need_log_sync,
WriteContext* write_context) {
mutex_.AssertHeld();
assert(write_context != nullptr && need_log_sync != nullptr);
Status status;
if (error_handler_.IsDBStopped()) {
status = error_handler_.GetBGError();
}
PERF_TIMER_GUARD(write_scheduling_flushes_compactions_time);
assert(!single_column_family_mode_ ||
versions_->GetColumnFamilySet()->NumberOfColumnFamilies() == 1);
if (UNLIKELY(status.ok() && !single_column_family_mode_ &&
total_log_size_ > GetMaxTotalWalSize())) {
status = SwitchWAL(write_context);
}
if (UNLIKELY(status.ok() && write_buffer_manager_->ShouldFlush())) {
// Before a new memtable is added in SwitchMemtable(),
// write_buffer_manager_->ShouldFlush() will keep returning true. If another
// thread is writing to another DB with the same write buffer, they may also
// be flushed. We may end up with flushing much more DBs than needed. It's
// suboptimal but still correct.
status = HandleWriteBufferFull(write_context);
}
if (UNLIKELY(status.ok() && !flush_scheduler_.Empty())) {
status = ScheduleFlushes(write_context);
}
PERF_TIMER_STOP(write_scheduling_flushes_compactions_time);
PERF_TIMER_GUARD(write_pre_and_post_process_time);
if (UNLIKELY(status.ok() && (write_controller_.IsStopped() ||
write_controller_.NeedsDelay()))) {
PERF_TIMER_STOP(write_pre_and_post_process_time);
PERF_TIMER_GUARD(write_delay_time);
// We don't know size of curent batch so that we always use the size
// for previous one. It might create a fairness issue that expiration
// might happen for smaller writes but larger writes can go through.
// Can optimize it if it is an issue.
status = DelayWrite(last_batch_group_size_, write_options);
PERF_TIMER_START(write_pre_and_post_process_time);
}
if (status.ok() && *need_log_sync) {
// Wait until the parallel syncs are finished. Any sync process has to sync
// the front log too so it is enough to check the status of front()
// We do a while loop since log_sync_cv_ is signalled when any sync is
// finished
// Note: there does not seem to be a reason to wait for parallel sync at
// this early step but it is not important since parallel sync (SyncWAL) and
// need_log_sync are usually not used together.
while (logs_.front().getting_synced) {
log_sync_cv_.Wait();
}
for (auto& log : logs_) {
assert(!log.getting_synced);
// This is just to prevent the logs to be synced by a parallel SyncWAL
// call. We will do the actual syncing later after we will write to the
// WAL.
// Note: there does not seem to be a reason to set this early before we
// actually write to the WAL
log.getting_synced = true;
}
} else {
*need_log_sync = false;
}
return status;
}
WriteBatch* DBImpl::MergeBatch(const WriteThread::WriteGroup& write_group,
WriteBatch* tmp_batch, size_t* write_with_wal,
WriteBatch** to_be_cached_state) {
assert(write_with_wal != nullptr);
assert(tmp_batch != nullptr);
assert(*to_be_cached_state == nullptr);
WriteBatch* merged_batch = nullptr;
*write_with_wal = 0;
auto* leader = write_group.leader;
assert(!leader->disable_wal); // Same holds for all in the batch group
if (write_group.size == 1 && !leader->CallbackFailed() &&
leader->batch->GetWalTerminationPoint().is_cleared()) {
// we simply write the first WriteBatch to WAL if the group only
// contains one batch, that batch should be written to the WAL,
// and the batch is not wanting to be truncated
merged_batch = leader->batch;
if (WriteBatchInternal::IsLatestPersistentState(merged_batch)) {
*to_be_cached_state = merged_batch;
}
*write_with_wal = 1;
} else {
// WAL needs all of the batches flattened into a single batch.
// We could avoid copying here with an iov-like AddRecord
// interface
merged_batch = tmp_batch;
for (auto writer : write_group) {
if (!writer->CallbackFailed()) {
WriteBatchInternal::Append(merged_batch, writer->batch,
/*WAL_only*/ true);
if (WriteBatchInternal::IsLatestPersistentState(writer->batch)) {
// We only need to cache the last of such write batch
*to_be_cached_state = writer->batch;
}
(*write_with_wal)++;
}
}
}
return merged_batch;
}
// When two_write_queues_ is disabled, this function is called from the only
// write thread. Otherwise this must be called holding log_write_mutex_.
Status DBImpl::WriteToWAL(const WriteBatch& merged_batch,
log::Writer* log_writer, uint64_t* log_used,
uint64_t* log_size) {
assert(log_size != nullptr);
Slice log_entry = WriteBatchInternal::Contents(&merged_batch);
*log_size = log_entry.size();
// When two_write_queues_ WriteToWAL has to be protected from concurretn calls
// from the two queues anyway and log_write_mutex_ is already held. Otherwise
// if manual_wal_flush_ is enabled we need to protect log_writer->AddRecord
// from possible concurrent calls via the FlushWAL by the application.
const bool needs_locking = manual_wal_flush_ && !two_write_queues_;
// Due to performance cocerns of missed branch prediction penalize the new
// manual_wal_flush_ feature (by UNLIKELY) instead of the more common case
// when we do not need any locking.
if (UNLIKELY(needs_locking)) {
log_write_mutex_.Lock();
}
Status status = log_writer->AddRecord(log_entry);
if (UNLIKELY(needs_locking)) {
log_write_mutex_.Unlock();
}
if (log_used != nullptr) {
*log_used = logfile_number_;
}
total_log_size_ += log_entry.size();
// TODO(myabandeh): it might be unsafe to access alive_log_files_.back() here
// since alive_log_files_ might be modified concurrently
alive_log_files_.back().AddSize(log_entry.size());
log_empty_ = false;
return status;
}
Status DBImpl::WriteToWAL(const WriteThread::WriteGroup& write_group,
log::Writer* log_writer, uint64_t* log_used,
bool need_log_sync, bool need_log_dir_sync,
SequenceNumber sequence) {
Status status;
assert(!write_group.leader->disable_wal);
// Same holds for all in the batch group
size_t write_with_wal = 0;
WriteBatch* to_be_cached_state = nullptr;
WriteBatch* merged_batch = MergeBatch(write_group, &tmp_batch_,
&write_with_wal, &to_be_cached_state);
if (merged_batch == write_group.leader->batch) {
write_group.leader->log_used = logfile_number_;
} else if (write_with_wal > 1) {
for (auto writer : write_group) {
writer->log_used = logfile_number_;
}
}
WriteBatchInternal::SetSequence(merged_batch, sequence);
uint64_t log_size;
status = WriteToWAL(*merged_batch, log_writer, log_used, &log_size);
if (to_be_cached_state) {
cached_recoverable_state_ = *to_be_cached_state;
cached_recoverable_state_empty_ = false;
}
if (status.ok() && need_log_sync) {
StopWatch sw(env_, stats_, WAL_FILE_SYNC_MICROS);
// It's safe to access logs_ with unlocked mutex_ here because:
// - we've set getting_synced=true for all logs,
// so other threads won't pop from logs_ while we're here,
// - only writer thread can push to logs_, and we're in
// writer thread, so no one will push to logs_,
// - as long as other threads don't modify it, it's safe to read
// from std::deque from multiple threads concurrently.
for (auto& log : logs_) {
status = log.writer->file()->Sync(immutable_db_options_.use_fsync);
if (!status.ok()) {
break;
}
}
if (status.ok() && need_log_dir_sync) {
// We only sync WAL directory the first time WAL syncing is
// requested, so that in case users never turn on WAL sync,
// we can avoid the disk I/O in the write code path.
status = directories_.GetWalDir()->Fsync();
}
}
if (merged_batch == &tmp_batch_) {
tmp_batch_.Clear();
}
if (status.ok()) {
auto stats = default_cf_internal_stats_;
if (need_log_sync) {
stats->AddDBStats(InternalStats::WAL_FILE_SYNCED, 1);
RecordTick(stats_, WAL_FILE_SYNCED);
}
stats->AddDBStats(InternalStats::WAL_FILE_BYTES, log_size);
RecordTick(stats_, WAL_FILE_BYTES, log_size);
stats->AddDBStats(InternalStats::WRITE_WITH_WAL, write_with_wal);
RecordTick(stats_, WRITE_WITH_WAL, write_with_wal);
}
return status;
}
Status DBImpl::ConcurrentWriteToWAL(const WriteThread::WriteGroup& write_group,
uint64_t* log_used,
SequenceNumber* last_sequence,
size_t seq_inc) {
Status status;
assert(!write_group.leader->disable_wal);
// Same holds for all in the batch group
WriteBatch tmp_batch;
size_t write_with_wal = 0;
WriteBatch* to_be_cached_state = nullptr;
WriteBatch* merged_batch =
MergeBatch(write_group, &tmp_batch, &write_with_wal, &to_be_cached_state);
// We need to lock log_write_mutex_ since logs_ and alive_log_files might be
// pushed back concurrently
log_write_mutex_.Lock();
if (merged_batch == write_group.leader->batch) {
write_group.leader->log_used = logfile_number_;
} else if (write_with_wal > 1) {
for (auto writer : write_group) {
writer->log_used = logfile_number_;
}
}
*last_sequence = versions_->FetchAddLastAllocatedSequence(seq_inc);
auto sequence = *last_sequence + 1;
WriteBatchInternal::SetSequence(merged_batch, sequence);
log::Writer* log_writer = logs_.back().writer;
uint64_t log_size;
status = WriteToWAL(*merged_batch, log_writer, log_used, &log_size);
if (to_be_cached_state) {
cached_recoverable_state_ = *to_be_cached_state;
cached_recoverable_state_empty_ = false;
}
log_write_mutex_.Unlock();
if (status.ok()) {
const bool concurrent = true;
auto stats = default_cf_internal_stats_;
stats->AddDBStats(InternalStats::WAL_FILE_BYTES, log_size, concurrent);
RecordTick(stats_, WAL_FILE_BYTES, log_size);
stats->AddDBStats(InternalStats::WRITE_WITH_WAL, write_with_wal,
concurrent);
RecordTick(stats_, WRITE_WITH_WAL, write_with_wal);
}
return status;
}
Status DBImpl::WriteRecoverableState() {
mutex_.AssertHeld();
if (!cached_recoverable_state_empty_) {
bool dont_care_bool;
SequenceNumber next_seq;
if (two_write_queues_) {
log_write_mutex_.Lock();
}
SequenceNumber seq;
if (two_write_queues_) {
seq = versions_->FetchAddLastAllocatedSequence(0);
} else {
seq = versions_->LastSequence();
}
WriteBatchInternal::SetSequence(&cached_recoverable_state_, seq + 1);
auto status = WriteBatchInternal::InsertInto(
&cached_recoverable_state_, column_family_memtables_.get(),
&flush_scheduler_, true, 0 /*recovery_log_number*/, this,
false /* concurrent_memtable_writes */, &next_seq, &dont_care_bool,
seq_per_batch_);
auto last_seq = next_seq - 1;
if (two_write_queues_) {
versions_->FetchAddLastAllocatedSequence(last_seq - seq);
versions_->SetLastPublishedSequence(last_seq);
}
versions_->SetLastSequence(last_seq);
if (two_write_queues_) {
log_write_mutex_.Unlock();
}
if (status.ok() && recoverable_state_pre_release_callback_) {
const bool DISABLE_MEMTABLE = true;
for (uint64_t sub_batch_seq = seq + 1;
sub_batch_seq < next_seq && status.ok(); sub_batch_seq++) {
status = recoverable_state_pre_release_callback_->Callback(
sub_batch_seq, !DISABLE_MEMTABLE);
}
}
if (status.ok()) {
cached_recoverable_state_.Clear();
cached_recoverable_state_empty_ = true;
}
return status;
}
return Status::OK();
}
void DBImpl::SelectColumnFamiliesForAtomicFlush(
autovector<ColumnFamilyData*>* cfds) {
for (ColumnFamilyData* cfd : *versions_->GetColumnFamilySet()) {
if (cfd->IsDropped()) {
continue;
}
if (cfd->imm()->NumNotFlushed() != 0 || !cfd->mem()->IsEmpty() ||
!cached_recoverable_state_empty_.load()) {
cfds->push_back(cfd);
}
}
}
// Assign sequence number for atomic flush.
void DBImpl::AssignAtomicFlushSeq(const autovector<ColumnFamilyData*>& cfds) {
assert(atomic_flush_);
auto seq = versions_->LastSequence();
for (auto cfd : cfds) {
cfd->imm()->AssignAtomicFlushSeq(seq);
}
}
Status DBImpl::SwitchWAL(WriteContext* write_context) {
mutex_.AssertHeld();
assert(write_context != nullptr);
Status status;
if (alive_log_files_.begin()->getting_flushed) {
return status;
}
auto oldest_alive_log = alive_log_files_.begin()->number;
bool flush_wont_release_oldest_log = false;
if (allow_2pc()) {
auto oldest_log_with_uncommited_prep =
logs_with_prep_tracker_.FindMinLogContainingOutstandingPrep();
assert(oldest_log_with_uncommited_prep == 0 ||
oldest_log_with_uncommited_prep >= oldest_alive_log);
if (oldest_log_with_uncommited_prep > 0 &&
oldest_log_with_uncommited_prep == oldest_alive_log) {
if (unable_to_release_oldest_log_) {
// we already attempted to flush all column families dependent on
// the oldest alive log but the log still contained uncommited
// transactions so there is still nothing that we can do.
return status;
} else {
ROCKS_LOG_WARN(
immutable_db_options_.info_log,
"Unable to release oldest log due to uncommited transaction");
unable_to_release_oldest_log_ = true;
flush_wont_release_oldest_log = true;
}
}
}
if (!flush_wont_release_oldest_log) {
// we only mark this log as getting flushed if we have successfully
// flushed all data in this log. If this log contains outstanding prepared
// transactions then we cannot flush this log until those transactions are commited.
unable_to_release_oldest_log_ = false;
alive_log_files_.begin()->getting_flushed = true;
}
ROCKS_LOG_INFO(immutable_db_options_.info_log,
"Flushing all column families with data in WAL number %" PRIu64
". Total log size is %" PRIu64
" while max_total_wal_size is %" PRIu64,
oldest_alive_log, total_log_size_.load(), GetMaxTotalWalSize());
// no need to refcount because drop is happening in write thread, so can't
// happen while we're in the write thread
autovector<ColumnFamilyData*> cfds;
if (atomic_flush_) {
SelectColumnFamiliesForAtomicFlush(&cfds);
} else {
for (auto cfd : *versions_->GetColumnFamilySet()) {
if (cfd->IsDropped()) {
continue;
}
if (cfd->OldestLogToKeep() <= oldest_alive_log) {
cfds.push_back(cfd);
}
}
}
for (const auto cfd : cfds) {
cfd->Ref();
status = SwitchMemtable(cfd, write_context);
cfd->Unref();
if (!status.ok()) {
break;
}
}
if (status.ok()) {
if (atomic_flush_) {
AssignAtomicFlushSeq(cfds);
}
for (auto cfd : cfds) {
cfd->imm()->FlushRequested();
}
FlushRequest flush_req;
GenerateFlushRequest(cfds, &flush_req);
SchedulePendingFlush(flush_req, FlushReason::kWriteBufferManager);
MaybeScheduleFlushOrCompaction();
}
return status;
}
Status DBImpl::HandleWriteBufferFull(WriteContext* write_context) {
mutex_.AssertHeld();
assert(write_context != nullptr);
Status status;
// Before a new memtable is added in SwitchMemtable(),
// write_buffer_manager_->ShouldFlush() will keep returning true. If another
// thread is writing to another DB with the same write buffer, they may also
// be flushed. We may end up with flushing much more DBs than needed. It's
// suboptimal but still correct.
ROCKS_LOG_INFO(
immutable_db_options_.info_log,
"Flushing column family with largest mem table size. Write buffer is "
"using %" PRIu64 " bytes out of a total of %" PRIu64 ".",
write_buffer_manager_->memory_usage(),
write_buffer_manager_->buffer_size());
// no need to refcount because drop is happening in write thread, so can't
// happen while we're in the write thread
autovector<ColumnFamilyData*> cfds;
if (atomic_flush_) {
SelectColumnFamiliesForAtomicFlush(&cfds);
} else {
ColumnFamilyData* cfd_picked = nullptr;
SequenceNumber seq_num_for_cf_picked = kMaxSequenceNumber;
for (auto cfd : *versions_->GetColumnFamilySet()) {
if (cfd->IsDropped()) {
continue;
}
if (!cfd->mem()->IsEmpty()) {
// We only consider active mem table, hoping immutable memtable is
// already in the process of flushing.
uint64_t seq = cfd->mem()->GetCreationSeq();
if (cfd_picked == nullptr || seq < seq_num_for_cf_picked) {
cfd_picked = cfd;
seq_num_for_cf_picked = seq;
}
}
}
if (cfd_picked != nullptr) {
cfds.push_back(cfd_picked);
}
}
for (const auto cfd : cfds) {
if (cfd->mem()->IsEmpty()) {
continue;
}
cfd->Ref();
status = SwitchMemtable(cfd, write_context);
cfd->Unref();
if (!status.ok()) {
break;
}
}
if (status.ok()) {
if (atomic_flush_) {
AssignAtomicFlushSeq(cfds);
}
for (const auto cfd : cfds) {
cfd->imm()->FlushRequested();
}
FlushRequest flush_req;
GenerateFlushRequest(cfds, &flush_req);
SchedulePendingFlush(flush_req, FlushReason::kWriteBufferFull);
MaybeScheduleFlushOrCompaction();
}
return status;
}
uint64_t DBImpl::GetMaxTotalWalSize() const {
mutex_.AssertHeld();
return mutable_db_options_.max_total_wal_size == 0
? 4 * max_total_in_memory_state_
: mutable_db_options_.max_total_wal_size;
}
// REQUIRES: mutex_ is held
// REQUIRES: this thread is currently at the front of the writer queue
Status DBImpl::DelayWrite(uint64_t num_bytes,
const WriteOptions& write_options) {
uint64_t time_delayed = 0;
bool delayed = false;
{
StopWatch sw(env_, stats_, WRITE_STALL, &time_delayed);
uint64_t delay = write_controller_.GetDelay(env_, num_bytes);
if (delay > 0) {
if (write_options.no_slowdown) {
return Status::Incomplete("Write stall");
}
TEST_SYNC_POINT("DBImpl::DelayWrite:Sleep");
// Notify write_thread_ about the stall so it can setup a barrier and
// fail any pending writers with no_slowdown
write_thread_.BeginWriteStall();
TEST_SYNC_POINT("DBImpl::DelayWrite:BeginWriteStallDone");
mutex_.Unlock();
// We will delay the write until we have slept for delay ms or
// we don't need a delay anymore
const uint64_t kDelayInterval = 1000;
uint64_t stall_end = sw.start_time() + delay;
while (write_controller_.NeedsDelay()) {
if (env_->NowMicros() >= stall_end) {
// We already delayed this write `delay` microseconds
break;
}
delayed = true;
// Sleep for 0.001 seconds
env_->SleepForMicroseconds(kDelayInterval);
}
mutex_.Lock();
write_thread_.EndWriteStall();
}
// Don't wait if there's a background error, even if its a soft error. We
// might wait here indefinitely as the background compaction may never
// finish successfully, resulting in the stall condition lasting
// indefinitely
while (error_handler_.GetBGError().ok() && write_controller_.IsStopped()) {
if (write_options.no_slowdown) {
return Status::Incomplete("Write stall");
}
delayed = true;
// Notify write_thread_ about the stall so it can setup a barrier and
// fail any pending writers with no_slowdown
write_thread_.BeginWriteStall();
TEST_SYNC_POINT("DBImpl::DelayWrite:Wait");
bg_cv_.Wait();
write_thread_.EndWriteStall();
}
}
assert(!delayed || !write_options.no_slowdown);
if (delayed) {
default_cf_internal_stats_->AddDBStats(InternalStats::WRITE_STALL_MICROS,
time_delayed);
RecordTick(stats_, STALL_MICROS, time_delayed);
}
// If DB is not in read-only mode and write_controller is not stopping
// writes, we can ignore any background errors and allow the write to
// proceed
Status s;
if (write_controller_.IsStopped()) {
// If writes are still stopped, it means we bailed due to a background
// error
s = Status::Incomplete(error_handler_.GetBGError().ToString());
}
if (error_handler_.IsDBStopped()) {
s = error_handler_.GetBGError();
}
return s;
}
Status DBImpl::ThrottleLowPriWritesIfNeeded(const WriteOptions& write_options,
WriteBatch* my_batch) {
assert(write_options.low_pri);
// This is called outside the DB mutex. Although it is safe to make the call,
// the consistency condition is not guaranteed to hold. It's OK to live with
// it in this case.
// If we need to speed compaction, it means the compaction is left behind
// and we start to limit low pri writes to a limit.
if (write_controller_.NeedSpeedupCompaction()) {
if (allow_2pc() && (my_batch->HasCommit() || my_batch->HasRollback())) {
// For 2PC, we only rate limit prepare, not commit.
return Status::OK();
}
if (write_options.no_slowdown) {
return Status::Incomplete();
} else {
assert(my_batch != nullptr);
// Rate limit those writes. The reason that we don't completely wait
// is that in case the write is heavy, low pri writes may never have
// a chance to run. Now we guarantee we are still slowly making
// progress.
PERF_TIMER_GUARD(write_delay_time);
write_controller_.low_pri_rate_limiter()->Request(
my_batch->GetDataSize(), Env::IO_HIGH, nullptr /* stats */,
RateLimiter::OpType::kWrite);
}
}
return Status::OK();
}
Status DBImpl::ScheduleFlushes(WriteContext* context) {
autovector<ColumnFamilyData*> cfds;
if (atomic_flush_) {
SelectColumnFamiliesForAtomicFlush(&cfds);
for (auto cfd : cfds) {
cfd->Ref();
}
flush_scheduler_.Clear();
} else {
ColumnFamilyData* tmp_cfd;
while ((tmp_cfd = flush_scheduler_.TakeNextColumnFamily()) != nullptr) {
cfds.push_back(tmp_cfd);
}
}
Status status;
for (auto& cfd : cfds) {
if (!cfd->mem()->IsEmpty()) {
status = SwitchMemtable(cfd, context);
}
if (cfd->Unref()) {
delete cfd;
cfd = nullptr;
}
if (!status.ok()) {
break;
}
}
if (status.ok()) {
if (atomic_flush_) {
AssignAtomicFlushSeq(cfds);
}
FlushRequest flush_req;
GenerateFlushRequest(cfds, &flush_req);
SchedulePendingFlush(flush_req, FlushReason::kWriteBufferFull);
MaybeScheduleFlushOrCompaction();
}
return status;
}
#ifndef ROCKSDB_LITE
void DBImpl::NotifyOnMemTableSealed(ColumnFamilyData* /*cfd*/,
const MemTableInfo& mem_table_info) {
if (immutable_db_options_.listeners.size() == 0U) {
return;
}
if (shutting_down_.load(std::memory_order_acquire)) {
return;
}
for (auto listener : immutable_db_options_.listeners) {
listener->OnMemTableSealed(mem_table_info);
}
}
#endif // ROCKSDB_LITE
// REQUIRES: mutex_ is held
// REQUIRES: this thread is currently at the front of the writer queue
Status DBImpl::SwitchMemtable(ColumnFamilyData* cfd, WriteContext* context) {
mutex_.AssertHeld();
WriteThread::Writer nonmem_w;
if (two_write_queues_) {
// SwitchMemtable is a rare event. To simply the reasoning, we make sure
// that there is no concurrent thread writing to WAL.
nonmem_write_thread_.EnterUnbatched(&nonmem_w, &mutex_);
}
unique_ptr<WritableFile> lfile;
log::Writer* new_log = nullptr;
MemTable* new_mem = nullptr;
// Recoverable state is persisted in WAL. After memtable switch, WAL might
// be deleted, so we write the state to memtable to be persisted as well.
Status s = WriteRecoverableState();
if (!s.ok()) {
return s;
}
// In case of pipelined write is enabled, wait for all pending memtable
// writers.
if (immutable_db_options_.enable_pipelined_write) {
// Memtable writers may call DB::Get in case max_successive_merges > 0,
// which may lock mutex. Unlocking mutex here to avoid deadlock.
mutex_.Unlock();
write_thread_.WaitForMemTableWriters();
mutex_.Lock();
}
// Attempt to switch to a new memtable and trigger flush of old.
// Do this without holding the dbmutex lock.
assert(versions_->prev_log_number() == 0);
if (two_write_queues_) {
log_write_mutex_.Lock();
}
bool creating_new_log = !log_empty_;
if (two_write_queues_) {
log_write_mutex_.Unlock();
}
uint64_t recycle_log_number = 0;
if (creating_new_log && immutable_db_options_.recycle_log_file_num &&
!log_recycle_files_.empty()) {
recycle_log_number = log_recycle_files_.front();
log_recycle_files_.pop_front();
}
uint64_t new_log_number =
creating_new_log ? versions_->NewFileNumber() : logfile_number_;
const MutableCFOptions mutable_cf_options = *cfd->GetLatestMutableCFOptions();
// Set memtable_info for memtable sealed callback
#ifndef ROCKSDB_LITE
MemTableInfo memtable_info;
memtable_info.cf_name = cfd->GetName();
memtable_info.first_seqno = cfd->mem()->GetFirstSequenceNumber();
memtable_info.earliest_seqno = cfd->mem()->GetEarliestSequenceNumber();
memtable_info.num_entries = cfd->mem()->num_entries();
memtable_info.num_deletes = cfd->mem()->num_deletes();
#endif // ROCKSDB_LITE
// Log this later after lock release. It may be outdated, e.g., if background
// flush happens before logging, but that should be ok.
int num_imm_unflushed = cfd->imm()->NumNotFlushed();
DBOptions db_options =
BuildDBOptions(immutable_db_options_, mutable_db_options_);
const auto preallocate_block_size =
GetWalPreallocateBlockSize(mutable_cf_options.write_buffer_size);
auto write_hint = CalculateWALWriteHint();
mutex_.Unlock();
{
std::string log_fname =
LogFileName(immutable_db_options_.wal_dir, new_log_number);
if (creating_new_log) {
EnvOptions opt_env_opt =
env_->OptimizeForLogWrite(env_options_, db_options);
if (recycle_log_number) {
ROCKS_LOG_INFO(immutable_db_options_.info_log,
"reusing log %" PRIu64 " from recycle list\n",
recycle_log_number);
std::string old_log_fname =
LogFileName(immutable_db_options_.wal_dir, recycle_log_number);
s = env_->ReuseWritableFile(log_fname, old_log_fname, &lfile,
opt_env_opt);
} else {
s = NewWritableFile(env_, log_fname, &lfile, opt_env_opt);
}
if (s.ok()) {
// Our final size should be less than write_buffer_size
// (compression, etc) but err on the side of caution.
// use preallocate_block_size instead
// of calling GetWalPreallocateBlockSize()
lfile->SetPreallocationBlockSize(preallocate_block_size);
lfile->SetWriteLifeTimeHint(write_hint);
unique_ptr<WritableFileWriter> file_writer(new WritableFileWriter(
std::move(lfile), log_fname, opt_env_opt, nullptr /* stats */,
immutable_db_options_.listeners));
new_log = new log::Writer(
std::move(file_writer), new_log_number,
immutable_db_options_.recycle_log_file_num > 0, manual_wal_flush_);
}
}
if (s.ok()) {
SequenceNumber seq = versions_->LastSequence();
new_mem = cfd->ConstructNewMemtable(mutable_cf_options, seq);
context->superversion_context.NewSuperVersion();
}
#ifndef ROCKSDB_LITE
// PLEASE NOTE: We assume that there are no failable operations
// after lock is acquired below since we are already notifying
// client about mem table becoming immutable.
NotifyOnMemTableSealed(cfd, memtable_info);
#endif //ROCKSDB_LITE
}
ROCKS_LOG_INFO(immutable_db_options_.info_log,
"[%s] New memtable created with log file: #%" PRIu64
". Immutable memtables: %d.\n",
cfd->GetName().c_str(), new_log_number, num_imm_unflushed);
mutex_.Lock();
if (s.ok() && creating_new_log) {
log_write_mutex_.Lock();
logfile_number_ = new_log_number;
assert(new_log != nullptr);
log_empty_ = true;
log_dir_synced_ = false;
if (!logs_.empty()) {
// Alway flush the buffer of the last log before switching to a new one
log::Writer* cur_log_writer = logs_.back().writer;
s = cur_log_writer->WriteBuffer();
if (!s.ok()) {
ROCKS_LOG_WARN(immutable_db_options_.info_log,
"[%s] Failed to switch from #%" PRIu64 " to #%" PRIu64
" WAL file -- %s\n",
cfd->GetName().c_str(), cur_log_writer->get_log_number(),
new_log_number);
}
}
logs_.emplace_back(logfile_number_, new_log);
alive_log_files_.push_back(LogFileNumberSize(logfile_number_));
log_write_mutex_.Unlock();
}
if (!s.ok()) {
// how do we fail if we're not creating new log?
assert(creating_new_log);
assert(!new_mem);
assert(!new_log);
if (two_write_queues_) {
nonmem_write_thread_.ExitUnbatched(&nonmem_w);
}
return s;
}
for (auto loop_cfd : *versions_->GetColumnFamilySet()) {
// all this is just optimization to delete logs that
// are no longer needed -- if CF is empty, that means it
// doesn't need that particular log to stay alive, so we just
// advance the log number. no need to persist this in the manifest
if (loop_cfd->mem()->GetFirstSequenceNumber() == 0 &&
loop_cfd->imm()->NumNotFlushed() == 0) {
if (creating_new_log) {
loop_cfd->SetLogNumber(logfile_number_);
}
loop_cfd->mem()->SetCreationSeq(versions_->LastSequence());
}
}
cfd->mem()->SetNextLogNumber(logfile_number_);
cfd->imm()->Add(cfd->mem(), &context->memtables_to_free_);
new_mem->Ref();
cfd->SetMemtable(new_mem);
InstallSuperVersionAndScheduleWork(cfd, &context->superversion_context,
mutable_cf_options);
if (two_write_queues_) {
nonmem_write_thread_.ExitUnbatched(&nonmem_w);
}
return s;
}
size_t DBImpl::GetWalPreallocateBlockSize(uint64_t write_buffer_size) const {
mutex_.AssertHeld();
size_t bsize = static_cast<size_t>(
write_buffer_size / 10 + write_buffer_size);
// Some users might set very high write_buffer_size and rely on
// max_total_wal_size or other parameters to control the WAL size.
if (mutable_db_options_.max_total_wal_size > 0) {
bsize = std::min<size_t>(bsize, static_cast<size_t>(
mutable_db_options_.max_total_wal_size));
}
if (immutable_db_options_.db_write_buffer_size > 0) {
bsize = std::min<size_t>(bsize, immutable_db_options_.db_write_buffer_size);
}
if (immutable_db_options_.write_buffer_manager &&
immutable_db_options_.write_buffer_manager->enabled()) {
bsize = std::min<size_t>(
bsize, immutable_db_options_.write_buffer_manager->buffer_size());
}
return bsize;
}
// Default implementations of convenience methods that subclasses of DB
// can call if they wish
Status DB::Put(const WriteOptions& opt, ColumnFamilyHandle* column_family,
const Slice& key, const Slice& value) {
// Pre-allocate size of write batch conservatively.
// 8 bytes are taken by header, 4 bytes for count, 1 byte for type,
// and we allocate 11 extra bytes for key length, as well as value length.
WriteBatch batch(key.size() + value.size() + 24);
Status s = batch.Put(column_family, key, value);
if (!s.ok()) {
return s;
}
return Write(opt, &batch);
}
Status DB::Delete(const WriteOptions& opt, ColumnFamilyHandle* column_family,
const Slice& key) {
WriteBatch batch;
batch.Delete(column_family, key);
return Write(opt, &batch);
}
Status DB::SingleDelete(const WriteOptions& opt,
ColumnFamilyHandle* column_family, const Slice& key) {
WriteBatch batch;
batch.SingleDelete(column_family, key);
return Write(opt, &batch);
}
Status DB::DeleteRange(const WriteOptions& opt,
ColumnFamilyHandle* column_family,
const Slice& begin_key, const Slice& end_key) {
WriteBatch batch;
batch.DeleteRange(column_family, begin_key, end_key);
return Write(opt, &batch);
}
Status DB::Merge(const WriteOptions& opt, ColumnFamilyHandle* column_family,
const Slice& key, const Slice& value) {
WriteBatch batch;
Status s = batch.Merge(column_family, key, value);
if (!s.ok()) {
return s;
}
return Write(opt, &batch);
}
} // namespace rocksdb
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