1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
|
/**
* Copyright (C) 2012 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the GNU Affero General Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include <memory>
#include "mongo/base/disallow_copying.h"
#include "mongo/base/status_with.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/repl/data_replicator_external_state.h"
#include "mongo/db/repl/oplog_buffer.h"
#include "mongo/db/repl/oplog_fetcher.h"
#include "mongo/db/repl/optime.h"
#include "mongo/db/repl/rollback_impl.h"
#include "mongo/db/repl/sync_source_resolver.h"
#include "mongo/stdx/condition_variable.h"
#include "mongo/stdx/functional.h"
#include "mongo/stdx/mutex.h"
#include "mongo/stdx/thread.h"
#include "mongo/util/net/hostandport.h"
namespace mongo {
class DBClientBase;
class OperationContext;
namespace repl {
class ReplicationCoordinator;
class ReplicationCoordinatorExternalState;
class StorageInterface;
class BackgroundSync {
MONGO_DISALLOW_COPYING(BackgroundSync);
public:
/**
* Stopped -> Starting -> Running
* ^ | |
* |__________|____________|
*
* In normal cases: Stopped -> Starting -> Running -> Stopped.
* It is also possible to transition directly from Starting to Stopped.
*
* We need a separate Starting state since part of the startup process involves reading from
* disk and we want to do that disk I/O in the bgsync thread, rather than whatever thread calls
* start().
*/
enum class ProducerState { Starting, Running, Stopped };
BackgroundSync(ReplicationCoordinatorExternalState* replicationCoordinatorExternalState,
std::unique_ptr<OplogBuffer> oplogBuffer);
// stop syncing (when this node becomes a primary, e.g.)
// During stepdown, the last fetched optime is not reset in order to keep track of the lastest
// optime in the buffer. However, the last fetched optime has to be reset after initial sync or
// rollback.
void stop(bool resetLastFetchedOptime);
/**
* Starts oplog buffer, task executor and producer thread, in that order.
*/
void startup(OperationContext* opCtx);
/**
* Signals producer thread to stop.
*/
void shutdown(OperationContext* opCtx);
/**
* Waits for producer thread to stop before shutting down the task executor and oplog buffer.
*/
void join(OperationContext* opCtx);
/**
* Returns true if shutdown() has been called.
* Once this returns true, nothing more will be added to the queue and consumers must shutdown.
*/
bool inShutdown() const;
// starts the sync target notifying thread
void notifierThread();
HostAndPort getSyncTarget() const;
// Interface implementation
bool peek(OperationContext* opCtx, BSONObj* op);
void consume(OperationContext* opCtx);
void clearSyncTarget();
void waitForMore();
// For monitoring
BSONObj getCounters();
// Clears any fetched and buffered oplog entries.
void clearBuffer(OperationContext* opCtx);
/**
* Returns true if any of the following is true:
* 1) We are shutting down;
* 2) We are primary;
* 3) We are in drain mode; or
* 4) We are stopped.
*/
bool shouldStopFetching() const;
ProducerState getState() const;
// Starts the producer if it's stopped. Otherwise, let it keep running.
void startProducerIfStopped();
// Adds a fake oplog entry to buffer. Used for testing only.
void pushTestOpToBuffer(OperationContext* opCtx, const BSONObj& op);
private:
bool _inShutdown_inlock() const;
/**
* Starts the producer thread which runs until shutdown. Upon resolving the current sync source
* the producer thread uses the OplogFetcher (which requires the replication coordinator
* external state at construction) to fetch oplog entries from the source's oplog via a long
* running find query.
*/
void _run();
// Production thread inner loop.
void _runProducer();
void _produce(OperationContext* opCtx);
/**
* Checks current background sync state before pushing operations into blocking queue and
* updating metrics. If the queue is full, might block.
*
* requiredRBID is reset to empty after the first call.
*/
Status _enqueueDocuments(Fetcher::Documents::const_iterator begin,
Fetcher::Documents::const_iterator end,
const OplogFetcher::DocumentsInfo& info);
/**
* Executes a rollback.
*/
void _runRollback(OperationContext* opCtx,
const Status& fetcherReturnStatus,
const HostAndPort& source,
int requiredRBID,
StorageInterface* storageInterface);
// restart syncing
void start(OperationContext* opCtx);
OpTimeWithHash _readLastAppliedOpTimeWithHash(OperationContext* opCtx);
// Production thread
std::unique_ptr<OplogBuffer> _oplogBuffer;
// A pointer to the replication coordinator running the show.
ReplicationCoordinator* _replCoord;
// A pointer to the replication coordinator external state.
ReplicationCoordinatorExternalState* _replicationCoordinatorExternalState;
// _mutex protects all of the class variables declared below.
//
// Never hold bgsync mutex when trying to acquire the ReplicationCoordinator mutex.
mutable stdx::mutex _mutex;
OpTime _lastOpTimeFetched;
// lastFetchedHash is used to match ops to determine if we need to rollback, when
// a secondary.
long long _lastFetchedHash = 0LL;
// Thread running producerThread().
std::unique_ptr<stdx::thread> _producerThread;
// Set to true if shutdown() has been called.
bool _inShutdown = false;
ProducerState _state = ProducerState::Starting;
HostAndPort _syncSourceHost;
// Current sync source resolver validating sync source candidates.
// Pointer may be read on any thread that locks _mutex or unlocked on the BGSync thread. It can
// only be written to by the BGSync thread while holding _mutex.
std::unique_ptr<SyncSourceResolver> _syncSourceResolver;
// Current oplog fetcher tailing the oplog on the sync source.
std::unique_ptr<OplogFetcher> _oplogFetcher;
// Current rollback process. If this component is active, we are currently reverting local
// operations in the local oplog in order to bring this server to a consistent state relative
// to the sync source.
std::unique_ptr<RollbackImpl> _rollback;
};
} // namespace repl
} // namespace mongo
|
