rocksdb/db/version_builder.h
Yanqin Jin 9358178edc Support for single-primary, multi-secondary instances (#4899)
Summary:
This PR allows RocksDB to run in single-primary, multi-secondary process mode.
The writer is a regular RocksDB (e.g. an `DBImpl`) instance playing the role of a primary.
Multiple `DBImplSecondary` processes (secondaries) share the same set of SST files, MANIFEST, WAL files with the primary. Secondaries tail the MANIFEST of the primary and apply updates to their own in-memory state of the file system, e.g. `VersionStorageInfo`.

This PR has several components:
1. (Originally in #4745). Add a `PathNotFound` subcode to `IOError` to denote the failure when a secondary tries to open a file which has been deleted by the primary.

2. (Similar to #4602). Add `FragmentBufferedReader` to handle partially-read, trailing record at the end of a log from where future read can continue.

3. (Originally in #4710 and #4820). Add implementation of the secondary, i.e. `DBImplSecondary`.
3.1 Tail the primary's MANIFEST during recovery.
3.2 Tail the primary's MANIFEST during normal processing by calling `ReadAndApply`.
3.3 Tailing WAL will be in a future PR.

4. Add an example in 'examples/multi_processes_example.cc' to demonstrate the usage of secondary RocksDB instance in a multi-process setting. Instructions to run the example can be found at the beginning of the source code.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4899

Differential Revision: D14510945

Pulled By: riversand963

fbshipit-source-id: 4ac1c5693e6012ad23f7b4b42d3c374fecbe8886
2019-03-26 16:45:31 -07:00

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1.8 KiB
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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.
//
#pragma once
#include "rocksdb/env.h"
#include "rocksdb/slice_transform.h"
namespace rocksdb {
class TableCache;
class VersionStorageInfo;
class VersionEdit;
struct FileMetaData;
class InternalStats;
// A helper class so we can efficiently apply a whole sequence
// of edits to a particular state without creating intermediate
// Versions that contain full copies of the intermediate state.
class VersionBuilder {
public:
VersionBuilder(const EnvOptions& env_options, TableCache* table_cache,
VersionStorageInfo* base_vstorage, Logger* info_log = nullptr);
~VersionBuilder();
void CheckConsistency(VersionStorageInfo* vstorage);
void CheckConsistencyForDeletes(VersionEdit* edit, uint64_t number,
int level);
bool CheckConsistencyForNumLevels();
void Apply(VersionEdit* edit);
void SaveTo(VersionStorageInfo* vstorage);
Status LoadTableHandlers(InternalStats* internal_stats, int max_threads,
bool prefetch_index_and_filter_in_cache,
bool is_initial_load,
const SliceTransform* prefix_extractor);
void MaybeAddFile(VersionStorageInfo* vstorage, int level, FileMetaData* f);
private:
class Rep;
Rep* rep_;
};
extern bool NewestFirstBySeqNo(FileMetaData* a, FileMetaData* b);
} // namespace rocksdb