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
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
|
/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* 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
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* 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 Server Side 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.
*/
#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kTransaction
#include "mongo/platform/basic.h"
#include "mongo/db/auth/authorization_session.h"
#include "mongo/db/commands.h"
#include "mongo/db/commands/txn_two_phase_commit_cmds_gen.h"
#include "mongo/db/repl/repl_client_info.h"
#include "mongo/db/s/sharding_state.h"
#include "mongo/db/s/transaction_coordinator_service.h"
#include "mongo/db/session_catalog_mongod.h"
#include "mongo/db/transaction_participant.h"
#include "mongo/rpc/get_status_from_command_result.h"
#include "mongo/util/log.h"
namespace mongo {
namespace {
MONGO_FAIL_POINT_DEFINE(hangAfterStartingCoordinateCommit);
MONGO_FAIL_POINT_DEFINE(participantReturnNetworkErrorForPrepareAfterExecutingPrepareLogic);
class PrepareTransactionCmd : public TypedCommand<PrepareTransactionCmd> {
public:
class PrepareTimestamp {
public:
PrepareTimestamp(Timestamp timestamp) : _timestamp(std::move(timestamp)) {}
void serialize(BSONObjBuilder* bob) const {
bob->append("prepareTimestamp", _timestamp);
}
private:
Timestamp _timestamp;
};
using Request = PrepareTransaction;
using Response = PrepareTimestamp;
class Invocation final : public InvocationBase {
public:
using InvocationBase::InvocationBase;
Response typedRun(OperationContext* opCtx) {
if (!getTestCommandsEnabled() &&
serverGlobalParams.clusterRole != ClusterRole::ConfigServer) {
uassertStatusOK(ShardingState::get(opCtx)->canAcceptShardedCommands());
}
// If a node has majority read concern disabled, replication must use the legacy
// 'rollbackViaRefetch' algortithm, which does not support prepareTransaction oplog
// entries
uassert(ErrorCodes::ReadConcernMajorityNotEnabled,
"'prepareTransaction' is not supported with 'enableMajorityReadConcern=false'",
serverGlobalParams.enableMajorityReadConcern);
// Replica sets with arbiters are able to continually accept majority writes without
// actually being able to commit them (e.g. PSA with a downed secondary), which in turn
// will impact the liveness of 2PC transactions
const auto replCoord = repl::ReplicationCoordinator::get(opCtx);
uassert(ErrorCodes::ReadConcernMajorityNotEnabled,
"'prepareTransaction' is not supported for replica sets with arbiters",
!replCoord->setContainsArbiter());
// Standalone nodes do not support transactions at all
uassert(ErrorCodes::ReadConcernMajorityNotEnabled,
"'prepareTransaction' is not supported on standalone nodes.",
replCoord->isReplEnabled());
auto txnParticipant = TransactionParticipant::get(opCtx);
uassert(ErrorCodes::CommandFailed,
"prepareTransaction must be run within a transaction",
txnParticipant);
LOG(3)
<< "Participant shard received prepareTransaction for transaction with txnNumber "
<< opCtx->getTxnNumber() << " on session "
<< opCtx->getLogicalSessionId()->toBSON();
uassert(ErrorCodes::NoSuchTransaction,
"Transaction isn't in progress",
txnParticipant.transactionIsOpen());
if (txnParticipant.transactionIsPrepared()) {
auto& replClient = repl::ReplClientInfo::forClient(opCtx->getClient());
auto prepareOpTime = txnParticipant.getPrepareOpTime();
// Ensure waiting for writeConcern of the prepare OpTime. If the node has failed
// over, then we want to wait on an OpTime in the new term, so we wait on the
// lastApplied OpTime. If we've gotten to this point, then we are guaranteed that
// the transaction was prepared at this prepareOpTime on this branch of history and
// that waiting on this lastApplied OpTime waits on the prepareOpTime as well.
replClient.setLastOpToSystemLastOpTime(opCtx);
// TODO SERVER-39364: Due to a bug in setlastOpToSystemLastOpTime, the prepareOpTime
// may still be greater than the lastApplied. In that case we make sure that we wait
// on the prepareOpTime which is guaranteed to be in the current term. SERVER-39364
// can remove this extra setLastOp() call and just rely on the call to
// setLastOpToSystemLastOpTime() above.
if (prepareOpTime > replClient.getLastOp()) {
replClient.setLastOp(opCtx, prepareOpTime);
}
invariant(
opCtx->recoveryUnit()->getPrepareTimestamp() == prepareOpTime.getTimestamp(),
str::stream() << "recovery unit prepareTimestamp: "
<< opCtx->recoveryUnit()->getPrepareTimestamp().toString()
<< " participant prepareOpTime: " << prepareOpTime.toString());
if (MONGO_FAIL_POINT(
participantReturnNetworkErrorForPrepareAfterExecutingPrepareLogic)) {
uasserted(ErrorCodes::HostUnreachable,
"returning network error because failpoint is on");
}
return PrepareTimestamp(prepareOpTime.getTimestamp());
}
const auto prepareTimestamp = txnParticipant.prepareTransaction(opCtx, {});
if (MONGO_FAIL_POINT(
participantReturnNetworkErrorForPrepareAfterExecutingPrepareLogic)) {
uasserted(ErrorCodes::HostUnreachable,
"returning network error because failpoint is on");
}
return PrepareTimestamp(std::move(prepareTimestamp));
}
private:
bool supportsWriteConcern() const override {
return true;
}
NamespaceString ns() const override {
return NamespaceString(request().getDbName(), "");
}
void doCheckAuthorization(OperationContext* opCtx) const override {
uassert(ErrorCodes::Unauthorized,
"Unauthorized",
AuthorizationSession::get(opCtx->getClient())
->isAuthorizedForPrivilege(Privilege{ResourcePattern::forClusterResource(),
ActionType::internal}));
}
};
bool adminOnly() const override {
return true;
}
std::string help() const override {
return "Prepares a transaction on this shard; sent by a router or re-sent by the "
"transaction commit coordinator for a cross-shard transaction";
}
AllowedOnSecondary secondaryAllowed(ServiceContext*) const override {
return AllowedOnSecondary::kNever;
}
} prepareTransactionCmd;
std::set<ShardId> validateParticipants(OperationContext* opCtx,
const std::vector<mongo::CommitParticipant>& participants) {
StringBuilder ss;
std::set<ShardId> participantsSet;
ss << '[';
for (const auto& participant : participants) {
const auto& shardId = participant.getShardId();
const bool inserted = participantsSet.emplace(shardId).second;
uassert(51162,
str::stream() << "Participant list contains duplicate shard " << shardId,
inserted);
ss << shardId << ", ";
}
ss << ']';
LOG(3) << "Coordinator shard received request to coordinate commit with "
"participant list "
<< ss.str() << " for " << opCtx->getLogicalSessionId()->getId() << ':'
<< opCtx->getTxnNumber();
return participantsSet;
}
class CoordinateCommitTransactionCmd : public TypedCommand<CoordinateCommitTransactionCmd> {
public:
using Request = CoordinateCommitTransaction;
class Invocation final : public InvocationBase {
public:
using InvocationBase::InvocationBase;
void typedRun(OperationContext* opCtx) {
// Only config servers or initialized shard servers can act as transaction coordinators.
if (serverGlobalParams.clusterRole != ClusterRole::ConfigServer) {
uassertStatusOK(ShardingState::get(opCtx)->canAcceptShardedCommands());
}
const auto& cmd = request();
const auto tcs = TransactionCoordinatorService::get(opCtx);
// Coordinate the commit, or recover the commit decision from disk if this command was
// sent without a participant list.
auto coordinatorDecisionFuture = cmd.getParticipants().empty()
? tcs->recoverCommit(opCtx, *opCtx->getLogicalSessionId(), *opCtx->getTxnNumber())
: tcs->coordinateCommit(opCtx,
*opCtx->getLogicalSessionId(),
*opCtx->getTxnNumber(),
validateParticipants(opCtx, cmd.getParticipants()));
if (MONGO_FAIL_POINT(hangAfterStartingCoordinateCommit)) {
LOG(0) << "Hit hangAfterStartingCoordinateCommit failpoint";
MONGO_FAIL_POINT_PAUSE_WHILE_SET_OR_INTERRUPTED(opCtx,
hangAfterStartingCoordinateCommit);
}
ON_BLOCK_EXIT([opCtx] {
// A decision will most likely have been written from a different OperationContext
// (in all cases except the one where this command aborts the local participant), so
// ensure waiting for the client's writeConcern of the decision.
repl::ReplClientInfo::forClient(opCtx->getClient())
.setLastOpToSystemLastOpTime(opCtx);
});
if (coordinatorDecisionFuture) {
auto swCommitDecision = coordinatorDecisionFuture->getNoThrow(opCtx);
// The coordinator can only throw NoSuchTransaction (as opposed to propagating an
// Abort decision due to NoSuchTransaction reported by a shard) if
// cancelIfCommitNotYetStarted was called, which can happen in one of 3 cases:
//
// 1) The deadline to receive coordinateCommit passed
// 2) Transaction with a newer txnNumber started on the session before
// coordinateCommit was received
// 3) This is a sharded transaction, which used the optimized commit path and
// didn't require 2PC
//
// Even though only (3) requires recovering the commit decision from the local
// participant, since these cases cannot be differentiated currently, we always
// recover from the local participant.
if (swCommitDecision != ErrorCodes::NoSuchTransaction) {
auto commitDecision = uassertStatusOK(std::move(swCommitDecision));
switch (commitDecision) {
case txn::CommitDecision::kCommit:
return;
case txn::CommitDecision::kAbort:
uasserted(ErrorCodes::NoSuchTransaction, "Transaction was aborted");
}
}
}
// No coordinator was found in memory. Recover the decision from the local participant.
LOG(3) << "Going to recover decision from local participant for "
<< opCtx->getLogicalSessionId()->getId() << ':' << opCtx->getTxnNumber();
boost::optional<SharedSemiFuture<void>> participantExitPrepareFuture;
{
MongoDOperationContextSession sessionTxnState(opCtx);
auto txnParticipant = TransactionParticipant::get(opCtx);
txnParticipant.beginOrContinue(opCtx,
*opCtx->getTxnNumber(),
false /* autocommit */,
boost::none /* startTransaction */);
if (txnParticipant.transactionIsCommitted())
return;
if (txnParticipant.transactionIsInProgress()) {
txnParticipant.abortTransaction(opCtx);
}
participantExitPrepareFuture = txnParticipant.onExitPrepare();
}
// Wait for the participant to exit prepare.
participantExitPrepareFuture->get(opCtx);
{
MongoDOperationContextSession sessionTxnState(opCtx);
auto txnParticipant = TransactionParticipant::get(opCtx);
// Call beginOrContinue again in case the transaction number has changed.
txnParticipant.beginOrContinue(opCtx,
*opCtx->getTxnNumber(),
false /* autocommit */,
boost::none /* startTransaction */);
invariant(!txnParticipant.transactionIsOpen(),
"The participant should not be in progress after we waited for the "
"participant to complete");
uassert(ErrorCodes::NoSuchTransaction,
"Recovering the transaction's outcome found the transaction aborted",
txnParticipant.transactionIsCommitted());
}
}
private:
bool supportsWriteConcern() const override {
return true;
}
NamespaceString ns() const override {
return NamespaceString(request().getDbName(), "");
}
void doCheckAuthorization(OperationContext* opCtx) const override {}
};
bool adminOnly() const override {
return true;
}
std::string help() const override {
return "Coordinates the commit for a transaction. Only called by mongos.";
}
AllowedOnSecondary secondaryAllowed(ServiceContext*) const override {
return AllowedOnSecondary::kNever;
}
} coordinateCommitTransactionCmd;
} // namespace
} // namespace mongo
|