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
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
|
/**
* Copyright (C) 2014 MongoDB 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 "mongo/base/disallow_copying.h"
#include "mongo/base/status.h"
#include "mongo/db/storage/recovery_unit.h"
#include "mongo/db/concurrency/d_concurrency.h"
#include "mongo/db/write_concern_options.h"
#include "mongo/platform/atomic_word.h"
#include "mongo/util/decorable.h"
namespace mongo {
class Client;
class CurOp;
class Locker;
class ProgressMeter;
class StringData;
class WriteUnitOfWork;
/**
* This class encompasses the state required by an operation and lives from the time a network
* peration is dispatched until its execution is finished. Note that each "getmore" on a cursor
* is a separate operation. On construction, an OperationContext associates itself with the
* current client, and only on destruction it deassociates itself. At any time a client can be
* associated with at most one OperationContext. Each OperationContext has a RecoveryUnit
* associated with it, though the lifetime is not necesarily the same, see releaseRecoveryUnit
* and setRecoveryUnit. The operation context also keeps track of some transaction state
* (RecoveryUnitState) to reduce complexity and duplication in the storage-engine specific
* RecoveryUnit and to allow better invariant checking.
*/
class OperationContext : public Decorable<OperationContext> {
MONGO_DISALLOW_COPYING(OperationContext);
public:
/**
* The RecoveryUnitState is used by WriteUnitOfWork to ensure valid state transitions.
*/
enum RecoveryUnitState {
kNotInUnitOfWork, // not in a unit of work, no writes allowed
kActiveUnitOfWork, // in a unit of work that still may either commit or abort
kFailedUnitOfWork // in a unit of work that has failed and must be aborted
};
virtual ~OperationContext() = default;
/**
* Interface for durability. Caller DOES NOT own pointer.
*/
virtual RecoveryUnit* recoveryUnit() const = 0;
/**
* Returns the RecoveryUnit (same return value as recoveryUnit()) but the caller takes
* ownership of the returned RecoveryUnit, and the OperationContext instance relinquishes
* ownership. Sets the RecoveryUnit to NULL.
*
* Used to transfer ownership of storage engine state from OperationContext
* to ClientCursor for getMore-able queries.
*
* Note that we don't allow the top-level locks to be stored across getMore.
* We rely on active cursors being killed when collections or databases are dropped,
* or when collection metadata changes.
*/
virtual RecoveryUnit* releaseRecoveryUnit() = 0;
/**
* Associates the OperatingContext with a different RecoveryUnit for getMore or
* subtransactions, see RecoveryUnitSwap. The new state is passed and the old state is
* returned separately even though the state logically belongs to the RecoveryUnit,
* as it is managed by the OperationContext.
*/
virtual RecoveryUnitState setRecoveryUnit(RecoveryUnit* unit, RecoveryUnitState state) = 0;
/**
* Interface for locking. Caller DOES NOT own pointer.
*/
Locker* lockState() const { return _locker; }
// --- operation level info? ---
/**
* Raises a UserAssertion if this operation is in a killed state.
*/
virtual void checkForInterrupt() = 0;
/**
* Returns Status::OK() unless this operation is in a killed state.
*/
virtual Status checkForInterruptNoAssert() = 0;
/**
* Delegates to CurOp, but is included here to break dependencies.
* Caller does not own the pointer.
*/
virtual ProgressMeter* setMessage(const char* msg,
const std::string& name = "Progress",
unsigned long long progressMeterTotal = 0,
int secondsBetween = 3) = 0;
/**
* Delegates to CurOp, but is included here to break dependencies.
*
* TODO: We return a string because of hopefully transient CurOp thread-unsafe insanity.
*/
virtual std::string getNS() const = 0;
/**
* Returns the client under which this context runs.
*/
Client* getClient() const;
virtual uint64_t getRemainingMaxTimeMicros() const = 0;
/**
* Returns the operation ID associated with this operation.
*/
unsigned int getOpID() const { return _opId; }
/**
* @return true if this instance is primary for this namespace
*/
virtual bool isPrimaryFor( StringData ns ) = 0;
/**
* Returns WriteConcernOptions of the current operation
*/
const WriteConcernOptions& getWriteConcern() const {
return _writeConcern;
}
void setWriteConcern(const WriteConcernOptions& writeConcern) {
_writeConcern = writeConcern;
}
/**
* Set whether or not operations should generate oplog entries.
*/
virtual void setReplicatedWrites(bool writesAreReplicated = true) = 0;
/**
* Returns true if operations should generate oplog entries.
*/
virtual bool writesAreReplicated() const = 0;
/**
* Marks this operation as killed.
*
* Subsequent calls to checkForInterrupt and checkForInterruptNoAssert by the thread
* executing the operation will indicate that the operation has been killed.
*
* May be called by any thread that has locked the Client owning this operation context,
* or by the thread executing on behalf of this operation context.
*/
void markKilled();
/**
* Returns true if markKilled has been called on this operation context.
*
* May be called by any thread that has locked the Client owning this operation context,
* or by the thread executing on behalf of this operation context.
*/
bool isKillPending() const;
protected:
OperationContext(Client* client,
unsigned int opId,
Locker* locker);
RecoveryUnitState _ruState = kNotInUnitOfWork;
private:
friend class WriteUnitOfWork;
Client* const _client;
const unsigned int _opId;
// The lifetime of locker is managed by subclasses of OperationContext, so it is not
// safe to access _locker in the destructor of OperationContext.
Locker* const _locker;
AtomicInt32 _killPending{0};
WriteConcernOptions _writeConcern;
};
class WriteUnitOfWork {
MONGO_DISALLOW_COPYING(WriteUnitOfWork);
public:
WriteUnitOfWork(OperationContext* txn)
: _txn(txn),
_committed(false),
_toplevel(txn->_ruState == OperationContext::kNotInUnitOfWork) {
_txn->lockState()->beginWriteUnitOfWork();
if (_toplevel) {
_txn->recoveryUnit()->beginUnitOfWork(_txn);
_txn->_ruState = OperationContext::kActiveUnitOfWork;
}
}
~WriteUnitOfWork() {
if (!_committed) {
invariant(_txn->_ruState != OperationContext::kNotInUnitOfWork);
if (_toplevel) {
_txn->recoveryUnit()->abortUnitOfWork();
_txn->_ruState = OperationContext::kNotInUnitOfWork;
}
else {
_txn->_ruState = OperationContext::kFailedUnitOfWork;
}
_txn->lockState()->endWriteUnitOfWork();
}
}
void commit() {
invariant(!_committed);
invariant (_txn->_ruState == OperationContext::kActiveUnitOfWork);
if (_toplevel) {
_txn->recoveryUnit()->commitUnitOfWork();
_txn->_ruState = OperationContext::kNotInUnitOfWork;
}
_txn->lockState()->endWriteUnitOfWork();
_committed = true;
}
private:
OperationContext* const _txn;
bool _committed;
bool _toplevel;
};
/**
* RAII-style class to mark the scope of a transaction. ScopedTransactions may be nested.
* An outermost ScopedTransaction calls abandonSnapshot() on destruction, so that the storage
* engine can release resources, such as snapshots or locks, that it may have acquired during
* the transaction. Note that any writes are committed in nested WriteUnitOfWork scopes,
* so write conflicts cannot happen on completing a ScopedTransaction.
*
* TODO: The ScopedTransaction should hold the global lock
*/
class ScopedTransaction {
MONGO_DISALLOW_COPYING(ScopedTransaction);
public:
/**
* The mode for the transaction indicates whether the transaction will write (MODE_IX) or
* only read (MODE_IS), or needs to run without other writers (MODE_S) or any other
* operations (MODE_X) on the server.
*/
ScopedTransaction(OperationContext* txn, LockMode mode) : _txn(txn) { }
~ScopedTransaction() {
if (!_txn->lockState()->isLocked()) {
_txn->recoveryUnit()->abandonSnapshot();
}
}
private:
OperationContext* _txn;
};
} // namespace mongo
|