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
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
|
/**
* Copyright (C) 2015 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.
*/
#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kSharding
#include "mongo/platform/basic.h"
#include "mongo/db/s/migration_source_manager.h"
#include <set>
#include <vector>
#include "mongo/bson/bsonobjbuilder.h"
#include "mongo/db/concurrency/d_concurrency.h"
#include "mongo/db/db_raii.h"
#include "mongo/db/dbhelpers.h"
#include "mongo/db/exec/plan_stage.h"
#include "mongo/db/index/index_descriptor.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/query/internal_plans.h"
#include "mongo/db/record_id.h"
#include "mongo/logger/ramlog.h"
#include "mongo/s/chunk.h"
#include "mongo/s/d_state.h"
#include "mongo/s/shard_key_pattern.h"
#include "mongo/util/elapsed_tracker.h"
#include "mongo/util/log.h"
namespace mongo {
using std::list;
using std::string;
using std::unique_ptr;
namespace {
Tee* migrateLog = RamLog::get("migrate");
/**
* Used to receive invalidation notifications.
*
* XXX: move to the exec/ directory.
*/
class DeleteNotificationStage final : public PlanStage {
public:
DeleteNotificationStage(MigrationSourceManager* migrationSourceManager)
: PlanStage("NOTIFY_DELETE", nullptr), _migrationSourceManager(migrationSourceManager) {}
void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type) override {
if (type == INVALIDATION_DELETION) {
_migrationSourceManager->aboutToDelete(dl);
}
}
StageState work(WorkingSetID* out) override {
MONGO_UNREACHABLE;
}
bool isEOF() final {
MONGO_UNREACHABLE;
}
unique_ptr<PlanStageStats> getStats() final {
MONGO_UNREACHABLE;
}
SpecificStats* getSpecificStats() const final {
MONGO_UNREACHABLE;
}
StageType stageType() const final {
return STAGE_NOTIFY_DELETE;
}
private:
MigrationSourceManager* const _migrationSourceManager;
};
bool isInRange(const BSONObj& obj,
const BSONObj& min,
const BSONObj& max,
const BSONObj& shardKeyPattern) {
ShardKeyPattern shardKey(shardKeyPattern);
BSONObj k = shardKey.extractShardKeyFromDoc(obj);
return k.woCompare(min) >= 0 && k.woCompare(max) < 0;
}
} // namespace
/**
* Used to commit work for LogOpForSharding. Used to keep track of changes in documents that are
* part of a chunk being migrated.
*/
class LogOpForShardingHandler final : public RecoveryUnit::Change {
public:
/**
* Invariant: idObj should belong to a document that is part of the active chunk being migrated
*/
LogOpForShardingHandler(MigrationSourceManager* migrateSourceManager,
const BSONObj& idObj,
const char op)
: _migrationSourceManager(migrateSourceManager), _idObj(idObj.getOwned()), _op(op) {}
void commit() override {
switch (_op) {
case 'd': {
stdx::lock_guard<stdx::mutex> sl(_migrationSourceManager->_mutex);
_migrationSourceManager->_deleted.push_back(_idObj);
_migrationSourceManager->_memoryUsed += _idObj.firstElement().size() + 5;
break;
}
case 'i':
case 'u': {
stdx::lock_guard<stdx::mutex> sl(_migrationSourceManager->_mutex);
_migrationSourceManager->_reload.push_back(_idObj);
_migrationSourceManager->_memoryUsed += _idObj.firstElement().size() + 5;
break;
}
default:
MONGO_UNREACHABLE;
}
}
void rollback() override {}
private:
MigrationSourceManager* const _migrationSourceManager;
const BSONObj _idObj;
const char _op;
};
MigrationSourceManager::MigrationSourceManager() = default;
MigrationSourceManager::~MigrationSourceManager() = default;
bool MigrationSourceManager::start(OperationContext* txn,
const std::string& ns,
const BSONObj& min,
const BSONObj& max,
const BSONObj& shardKeyPattern) {
invariant(!min.isEmpty());
invariant(!max.isEmpty());
invariant(!ns.empty());
// Get global shared to synchronize with logOp. Also see comments in the class
// members declaration for more details.
Lock::GlobalRead globalShared(txn->lockState());
stdx::lock_guard<stdx::mutex> lk(_mutex);
if (_active) {
return false;
}
_nss = NamespaceString(ns);
_min = min;
_max = max;
_shardKeyPattern = shardKeyPattern;
invariant(_deleted.size() == 0);
invariant(_reload.size() == 0);
invariant(_memoryUsed == 0);
_active = true;
stdx::lock_guard<stdx::mutex> tLock(_cloneLocsMutex);
invariant(_cloneLocs.size() == 0);
return true;
}
void MigrationSourceManager::done(OperationContext* txn) {
log() << "MigrateFromStatus::done About to acquire global lock to exit critical section";
// Get global shared to synchronize with logOp. Also see comments in the class
// members declaration for more details.
Lock::GlobalRead globalShared(txn->lockState());
stdx::lock_guard<stdx::mutex> lk(_mutex);
_active = false;
_deleteNotifyExec.reset(NULL);
_inCriticalSection = false;
_inCriticalSectionCV.notify_all();
_deleted.clear();
_reload.clear();
_memoryUsed = 0;
stdx::lock_guard<stdx::mutex> cloneLock(_cloneLocsMutex);
_cloneLocs.clear();
}
void MigrationSourceManager::logOp(OperationContext* txn,
const char* opstr,
const char* ns,
const BSONObj& obj,
BSONObj* patt,
bool notInActiveChunk) {
ensureShardVersionOKOrThrow(txn, ns);
const char op = opstr[0];
if (notInActiveChunk) {
// Ignore writes that came from the migration process like cleanup so they
// won't be transferred to the recipient shard. Also ignore ops from
// _migrateClone and _transferMods since it is impossible to move a chunk
// to self.
return;
}
dassert(txn->lockState()->isWriteLocked()); // Must have Global IX.
if (!_active)
return;
if (_nss != ns)
return;
// no need to log if this is not an insertion, an update, or an actual deletion
// note: opstr 'db' isn't a deletion but a mention that a database exists
// (for replication machinery mostly).
if (op == 'n' || op == 'c' || (op == 'd' && opstr[1] == 'b'))
return;
BSONElement ide;
if (patt)
ide = patt->getField("_id");
else
ide = obj["_id"];
if (ide.eoo()) {
warning() << "logOpForSharding got mod with no _id, ignoring obj: " << obj << migrateLog;
return;
}
if (op == 'i' && (!isInRange(obj, _min, _max, _shardKeyPattern))) {
return;
}
BSONObj idObj(ide.wrap());
if (op == 'u') {
BSONObj fullDoc;
OldClientContext ctx(txn, _nss.ns(), false);
if (!Helpers::findById(txn, ctx.db(), _nss.ns().c_str(), idObj, fullDoc)) {
warning() << "logOpForSharding couldn't find: " << idObj << " even though should have"
<< migrateLog;
dassert(false); // TODO: Abort the migration.
return;
}
if (!isInRange(fullDoc, _min, _max, _shardKeyPattern)) {
return;
}
}
// Note: can't check if delete is in active chunk since the document is gone!
txn->recoveryUnit()->registerChange(new LogOpForShardingHandler(this, idObj, op));
}
bool MigrationSourceManager::transferMods(OperationContext* txn,
string& errmsg,
BSONObjBuilder& b) {
long long size = 0;
{
AutoGetCollectionForRead ctx(txn, _getNS());
stdx::lock_guard<stdx::mutex> sl(_mutex);
if (!_active) {
errmsg = "no active migration!";
return false;
}
// TODO: fix SERVER-16540 race
_xfer(txn, _nss.ns(), ctx.getDb(), &_deleted, b, "deleted", size, false);
_xfer(txn, _nss.ns(), ctx.getDb(), &_reload, b, "reload", size, true);
}
b.append("size", size);
return true;
}
bool MigrationSourceManager::storeCurrentLocs(OperationContext* txn,
long long maxChunkSize,
string& errmsg,
BSONObjBuilder& result) {
AutoGetCollection autoColl(txn, _getNS(), MODE_IS);
Collection* collection = autoColl.getCollection();
if (!collection) {
errmsg = "ns not found, should be impossible";
return false;
}
// Allow multiKey based on the invariant that shard keys must be single-valued. Therefore, any
// multi-key index prefixed by shard key cannot be multikey over the shard key fields.
IndexDescriptor* idx =
collection->getIndexCatalog()->findShardKeyPrefixedIndex(txn,
_shardKeyPattern,
false); // requireSingleKey
if (idx == NULL) {
errmsg = str::stream() << "can't find index with prefix " << _shardKeyPattern
<< " in storeCurrentLocs for " << _nss.toString();
return false;
}
// Assume both min and max non-empty, append MinKey's to make them fit chosen index
BSONObj min;
BSONObj max;
KeyPattern kp(idx->keyPattern());
{
// It's alright not to lock _mutex all the way through based on the assumption that this is
// only called by the main thread that drives the migration and only it can start and stop
// the current migration.
stdx::lock_guard<stdx::mutex> sl(_mutex);
invariant(_deleteNotifyExec.get() == NULL);
unique_ptr<WorkingSet> ws = stdx::make_unique<WorkingSet>();
unique_ptr<DeleteNotificationStage> dns = stdx::make_unique<DeleteNotificationStage>(this);
// Takes ownership of 'ws' and 'dns'.
auto statusWithPlanExecutor = PlanExecutor::make(
txn, std::move(ws), std::move(dns), collection, PlanExecutor::YIELD_MANUAL);
invariant(statusWithPlanExecutor.isOK());
_deleteNotifyExec = std::move(statusWithPlanExecutor.getValue());
_deleteNotifyExec->registerExec();
min = Helpers::toKeyFormat(kp.extendRangeBound(_min, false));
max = Helpers::toKeyFormat(kp.extendRangeBound(_max, false));
}
unique_ptr<PlanExecutor> exec(InternalPlanner::indexScan(txn,
collection,
idx,
min,
max,
false, // endKeyInclusive
PlanExecutor::YIELD_MANUAL));
// We can afford to yield here because any change to the base data that we might miss is already
// being queued and will migrate in the 'transferMods' stage.
exec->setYieldPolicy(PlanExecutor::YIELD_AUTO);
// Use the average object size to estimate how many objects a full chunk would carry do that
// while traversing the chunk's range using the sharding index, below there's a fair amount of
// slack before we determine a chunk is too large because object sizes will vary.
unsigned long long maxRecsWhenFull;
long long avgRecSize;
const long long totalRecs = collection->numRecords(txn);
if (totalRecs > 0) {
avgRecSize = collection->dataSize(txn) / totalRecs;
maxRecsWhenFull = maxChunkSize / avgRecSize;
maxRecsWhenFull = std::min((unsigned long long)(Chunk::MaxObjectPerChunk + 1),
130 * maxRecsWhenFull / 100 /* slack */);
} else {
avgRecSize = 0;
maxRecsWhenFull = Chunk::MaxObjectPerChunk + 1;
}
// Do a full traversal of the chunk and don't stop even if we think it is a large chunk we want
// the number of records to better report, in that case
bool isLargeChunk = false;
unsigned long long recCount = 0;
RecordId recordId;
while (PlanExecutor::ADVANCED == exec->getNext(NULL, &recordId)) {
if (!isLargeChunk) {
stdx::lock_guard<stdx::mutex> lk(_cloneLocsMutex);
_cloneLocs.insert(recordId);
}
if (++recCount > maxRecsWhenFull) {
isLargeChunk = true;
// Continue on despite knowing that it will fail, just to get the correct value for
// recCount
}
}
exec.reset();
if (isLargeChunk) {
stdx::lock_guard<stdx::mutex> sl(_mutex);
warning() << "cannot move chunk: the maximum number of documents for a chunk is "
<< maxRecsWhenFull << " , the maximum chunk size is " << maxChunkSize
<< " , average document size is " << avgRecSize << ". Found " << recCount
<< " documents in chunk "
<< " ns: " << _nss << " " << _min << " -> " << _max << migrateLog;
result.appendBool("chunkTooBig", true);
result.appendNumber("estimatedChunkSize", (long long)(recCount * avgRecSize));
errmsg = "chunk too big to move";
return false;
}
log() << "moveChunk number of documents: " << cloneLocsRemaining() << migrateLog;
txn->recoveryUnit()->abandonSnapshot();
return true;
}
bool MigrationSourceManager::clone(OperationContext* txn, string& errmsg, BSONObjBuilder& result) {
ElapsedTracker tracker(internalQueryExecYieldIterations, internalQueryExecYieldPeriodMS);
int allocSize = 0;
{
AutoGetCollection autoColl(txn, _getNS(), MODE_IS);
stdx::lock_guard<stdx::mutex> sl(_mutex);
if (!_active) {
errmsg = "not active";
return false;
}
Collection* collection = autoColl.getCollection();
if (!collection) {
errmsg = str::stream() << "collection " << _nss.toString() << " does not exist";
return false;
}
allocSize = std::min(
BSONObjMaxUserSize,
static_cast<int>((12 + collection->averageObjectSize(txn)) * cloneLocsRemaining()));
}
bool isBufferFilled = false;
BSONArrayBuilder clonedDocsArrayBuilder(allocSize);
while (!isBufferFilled) {
AutoGetCollection autoColl(txn, _getNS(), MODE_IS);
stdx::lock_guard<stdx::mutex> sl(_mutex);
if (!_active) {
errmsg = "not active";
return false;
}
// TODO: fix SERVER-16540 race
Collection* collection = autoColl.getCollection();
if (!collection) {
errmsg = str::stream() << "collection " << _nss.toString() << " does not exist";
return false;
}
stdx::lock_guard<stdx::mutex> lk(_cloneLocsMutex);
std::set<RecordId>::iterator cloneLocsIter = _cloneLocs.begin();
for (; cloneLocsIter != _cloneLocs.end(); ++cloneLocsIter) {
if (tracker.intervalHasElapsed()) // should I yield?
break;
RecordId recordId = *cloneLocsIter;
Snapshotted<BSONObj> doc;
if (!collection->findDoc(txn, recordId, &doc)) {
// doc was deleted
continue;
}
// Use the builder size instead of accumulating 'doc's size so that we take
// into consideration the overhead of BSONArray indices, and *always*
// append one doc.
if (clonedDocsArrayBuilder.arrSize() != 0 &&
(clonedDocsArrayBuilder.len() + doc.value().objsize() + 1024) >
BSONObjMaxUserSize) {
isBufferFilled = true; // break out of outer while loop
break;
}
clonedDocsArrayBuilder.append(doc.value());
}
_cloneLocs.erase(_cloneLocs.begin(), cloneLocsIter);
// Note: must be holding _cloneLocsMutex, don't move this inside while condition!
if (_cloneLocs.empty()) {
break;
}
}
result.appendArray("objects", clonedDocsArrayBuilder.arr());
return true;
}
void MigrationSourceManager::aboutToDelete(const RecordId& dl) {
// Even though above we call findDoc to check for existance that check only works for non-mmapv1
// engines, and this is needed for mmapv1.
stdx::lock_guard<stdx::mutex> lk(_cloneLocsMutex);
_cloneLocs.erase(dl);
}
std::size_t MigrationSourceManager::cloneLocsRemaining() const {
stdx::lock_guard<stdx::mutex> lk(_cloneLocsMutex);
return _cloneLocs.size();
}
long long MigrationSourceManager::mbUsed() const {
stdx::lock_guard<stdx::mutex> lk(_mutex);
return _memoryUsed / (1024 * 1024);
}
bool MigrationSourceManager::getInCriticalSection() const {
stdx::lock_guard<stdx::mutex> lk(_mutex);
return _inCriticalSection;
}
void MigrationSourceManager::setInCriticalSection(bool inCritSec) {
stdx::lock_guard<stdx::mutex> lk(_mutex);
_inCriticalSection = inCritSec;
_inCriticalSectionCV.notify_all();
}
bool MigrationSourceManager::waitTillNotInCriticalSection(int maxSecondsToWait) {
const auto deadline = stdx::chrono::system_clock::now() + Seconds(maxSecondsToWait);
stdx::unique_lock<stdx::mutex> lk(_mutex);
while (_inCriticalSection) {
log() << "Waiting for " << maxSecondsToWait
<< " seconds for the migration critical section to end";
if (stdx::cv_status::timeout == _inCriticalSectionCV.wait_until(lk, deadline)) {
return false;
}
}
return true;
}
bool MigrationSourceManager::isActive() const {
stdx::lock_guard<stdx::mutex> lk(_mutex);
return _active;
}
void MigrationSourceManager::_xfer(OperationContext* txn,
const string& ns,
Database* db,
std::list<BSONObj>* docIdList,
BSONObjBuilder& builder,
const char* fieldName,
long long& size,
bool explode) {
const long long maxSize = 1024 * 1024;
if (docIdList->size() == 0 || size > maxSize) {
return;
}
BSONArrayBuilder arr(builder.subarrayStart(fieldName));
list<BSONObj>::iterator docIdIter = docIdList->begin();
while (docIdIter != docIdList->end() && size < maxSize) {
BSONObj idDoc = *docIdIter;
if (explode) {
BSONObj fullDoc;
if (Helpers::findById(txn, db, ns.c_str(), idDoc, fullDoc)) {
arr.append(fullDoc);
size += fullDoc.objsize();
}
} else {
arr.append(idDoc);
size += idDoc.objsize();
}
docIdIter = docIdList->erase(docIdIter);
}
arr.done();
}
NamespaceString MigrationSourceManager::_getNS() const {
stdx::lock_guard<stdx::mutex> lk(_mutex);
return _nss;
}
} // namespace mongo
|