rocksdb/db/write_thread.h

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// Copyright (c) 2013, 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.
#pragma once
#include <stdint.h>
#include <deque>
#include <limits>
#include "rocksdb/status.h"
#include "db/write_batch_internal.h"
#include "util/autovector.h"
#include "port/port.h"
namespace rocksdb {
class WriteThread {
public:
static const uint64_t kNoTimeOut = std::numeric_limits<uint64_t>::max();
// Information kept for every waiting writer
struct Writer {
Status status;
WriteBatch* batch;
bool sync;
bool disableWAL;
bool in_batch_group;
bool done;
uint64_t timeout_hint_us;
port::CondVar cv;
explicit Writer(port::Mutex* mu)
: batch(nullptr),
sync(false),
disableWAL(false),
in_batch_group(false),
done(false),
timeout_hint_us(kNoTimeOut),
cv(mu) {}
};
WriteThread() = default;
~WriteThread() = default;
// Before applying write operation (such as DBImpl::Write, DBImpl::Flush)
// thread should grab the mutex_ and be the first on writers queue.
// EnterWriteThread is used for it.
// Be aware! Writer's job can be done by other thread (see DBImpl::Write
// for examples), so check it via w.done before applying changes.
//
// Writer* w: writer to be placed in the queue
// uint64_t expiration_time: maximum time to be in the queue
// See also: ExitWriteThread
// REQUIRES: db mutex held
Status EnterWriteThread(Writer* w, uint64_t expiration_time);
// After doing write job, we need to remove already used writers from
// writers_ queue and notify head of the queue about it.
// ExitWriteThread is used for this.
//
// Writer* w: Writer, that was added by EnterWriteThread function
// Writer* last_writer: Since we can join a few Writers (as DBImpl::Write
// does)
// we should pass last_writer as a parameter to
// ExitWriteThread
// (if you don't touch other writers, just pass w)
// Status status: Status of write operation
// See also: EnterWriteThread
// REQUIRES: db mutex held
void ExitWriteThread(Writer* w, Writer* last_writer, Status status);
void BuildBatchGroup(Writer** last_writer,
autovector<WriteBatch*>* write_batch_group);
private:
// Queue of writers.
std::deque<Writer*> writers_;
};
} // namespace rocksdb