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
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
|
/* Copyright 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.
*/
#include "mongo/platform/basic.h"
#include "mongo/client/replica_set_monitor.h"
#include <algorithm>
#include <boost/thread.hpp>
#include <limits>
#include "mongo/db/server_options.h"
#include "mongo/client/connpool.h"
#include "mongo/client/replica_set_monitor_internal.h"
#include "mongo/util/concurrency/mutex.h" // for StaticObserver
#include "mongo/util/background.h"
#include "mongo/util/log.h"
#include "mongo/util/string_map.h"
#include "mongo/util/timer.h"
#if 0 // enable this to ease debugging of this file.
#undef DEV
#define DEV if (true)
#undef LOG
#define LOG(x) log()
#endif
namespace mongo {
MONGO_LOG_DEFAULT_COMPONENT_FILE(::mongo::logger::LogComponent::kNetworking);
namespace {
// Pull nested types to top-level scope
typedef ReplicaSetMonitor::IsMasterReply IsMasterReply;
typedef ReplicaSetMonitor::ScanState ScanState;
typedef ReplicaSetMonitor::ScanStatePtr ScanStatePtr;
typedef ReplicaSetMonitor::SetState SetState;
typedef ReplicaSetMonitor::SetStatePtr SetStatePtr;
typedef ReplicaSetMonitor::Refresher Refresher;
typedef Refresher::NextStep NextStep;
typedef ScanState::UnconfirmedReplies UnconfirmedReplies;
typedef SetState::Node Node;
typedef SetState::Nodes Nodes;
const double socketTimeoutSecs = 5;
/* Replica Set Monitor shared state:
* If a program (such as one built with the C++ driver) exits (by either calling exit()
* or by returning from main()), static objects will be destroyed in the reverse order
* of their creation (within each translation unit (source code file)). This makes it
* vital that the order be explicitly controlled within the source file so that destroyed
* objects never reference objects that have been destroyed earlier.
*
* The order chosen below is intended to allow safe destruction in reverse order from
* construction order:
* setsLock -- mutex protecting _seedServers and _sets, destroyed last
* seedServers -- list (map) of servers
* sets -- list (map) of ReplicaSetMonitors
* replicaSetMonitorWatcher -- background job to check Replica Set members
* staticObserver -- sentinel to detect process termination
*
* Related to:
* SERVER-8891 -- Simple client fail with segmentation fault in mongoclient library
*
* Mutex locking order:
* Don't lock setsLock while holding any SetState::mutex. It is however safe to grab a
* SetState::mutex without holder setsLock, but then you can't grab setsLock until you
* release the SetState::mutex.
*/
mongo::mutex setsLock("ReplicaSetMonitor");
StringMap<set<HostAndPort> > seedServers;
StringMap<ReplicaSetMonitorPtr> sets;
// global background job responsible for checking every X amount of time
class ReplicaSetMonitorWatcher : public BackgroundJob {
public:
ReplicaSetMonitorWatcher():
_monitorMutex("ReplicaSetMonitorWatcher::_safego"),
_started(false),
_stopRequested(false) {
}
~ReplicaSetMonitorWatcher() {
stop();
// We relying on the fact that if the monitor was rerun again, wait will not hang
// because _destroyingStatics will make the run method exit immediately.
dassert(StaticObserver::_destroyingStatics);
if (running()) {
wait();
}
}
virtual string name() const { return "ReplicaSetMonitorWatcher"; }
void safeGo() {
scoped_lock lk( _monitorMutex );
if ( _started )
return;
_started = true;
_stopRequested = false;
go();
}
/**
* Stops monitoring the sets and wait for the monitoring thread to terminate.
*/
void stop() {
scoped_lock sl( _monitorMutex );
_stopRequested = true;
_stopRequestedCV.notify_one();
}
protected:
void run() {
log() << "starting"; // includes thread name in output
// Added only for patching timing problems in test. Remove after tests
// are fixed - see 392b933598668768bf12b1e41ad444aa3548d970.
// Should not be needed after SERVER-7533 gets implemented and tests start
// using it.
if (!inShutdown() && !StaticObserver::_destroyingStatics) {
scoped_lock sl( _monitorMutex );
_stopRequestedCV.timed_wait(sl.boost(), boost::posix_time::seconds(10));
}
while ( !inShutdown() &&
!StaticObserver::_destroyingStatics ) {
{
scoped_lock sl( _monitorMutex );
if (_stopRequested) {
break;
}
}
try {
checkAllSets();
}
catch ( std::exception& e ) {
error() << "check failed: " << e.what();
}
catch ( ... ) {
error() << "unknown error";
}
scoped_lock sl( _monitorMutex );
if (_stopRequested) {
break;
}
_stopRequestedCV.timed_wait(sl.boost(), boost::posix_time::seconds(10));
}
}
void checkAllSets() {
// make a copy so we can quickly unlock setsLock
StringMap<ReplicaSetMonitorPtr> setsCopy;
{
scoped_lock lk( setsLock );
setsCopy = sets;
}
for (StringMap<ReplicaSetMonitorPtr>::const_iterator it = setsCopy.begin();
it != setsCopy.end(); ++it) {
LOG(1) << "checking replica set: " << it->first;
ReplicaSetMonitorPtr m = it->second;
m->startOrContinueRefresh().refreshAll();
const int numFails = m->getConsecutiveFailedScans();
if (numFails >= ReplicaSetMonitor::maxConsecutiveFailedChecks) {
log() << "Replica set " << m->getName() << " was down for " << numFails
<< " checks in a row. Stopping polled monitoring of the set.";
// locks setsLock
ReplicaSetMonitor::remove(m->getName(), false);
}
}
}
// protects _started, _stopRequested
mongo::mutex _monitorMutex;
bool _started;
boost::condition _stopRequestedCV;
bool _stopRequested;
} replicaSetMonitorWatcher;
StaticObserver staticObserver;
//
// Helpers for stl algorithms
//
bool isMaster(const Node& node) { return node.isMaster; }
bool compareLatencies(const Node* lhs, const Node* rhs) {
// NOTE: this automatically compares Node::unknownLatency worse than all others.
return lhs->latencyMicros < rhs->latencyMicros;
}
bool hostsEqual(const Node& lhs, const HostAndPort& rhs) { return lhs.host == rhs; }
// Allows comparing two Nodes, or a HostAndPort and a Node.
// NOTE: the two HostAndPort overload is only needed to support extra checks in some STL
// implementations. For simplicity, no comparator should be used with collections of just
// HostAndPort.
struct CompareHosts {
bool operator() (const Node& lhs, const Node& rhs) { return lhs.host < rhs.host; }
bool operator() (const Node& lhs, const HostAndPort& rhs) { return lhs.host < rhs; }
bool operator() (const HostAndPort& lhs, const Node& rhs) { return lhs < rhs.host; }
bool operator() (const HostAndPort& lhs, const HostAndPort& rhs) { return lhs < rhs; }
} compareHosts; // like an overloaded function, but able to pass to stl algorithms
// The following structs should be treated as functions returning a UnaryPredicate.
// Usage example: std::find_if(nodes.begin(), nodes.end(), hostIs(someHost));
// They all hold their constructor argument by reference.
struct hostIs {
explicit hostIs(const HostAndPort& host) :_host(host) {}
bool operator() (const HostAndPort& host) { return host == _host; }
bool operator() (const Node& node) { return node.host == _host; }
const HostAndPort& _host;
};
struct hostNotIn {
explicit hostNotIn(const std::set<HostAndPort>& hosts) :_hosts(hosts) {}
bool operator() (const HostAndPort& host) { return !_hosts.count(host); }
bool operator() (const Node& node) { return !_hosts.count(node.host); }
const std::set<HostAndPort>& _hosts;
};
} // namespace
// At 1 check every 10 seconds, 30 checks takes 5 minutes
int ReplicaSetMonitor::maxConsecutiveFailedChecks = 30;
// Defaults to random selection as required by the spec
bool ReplicaSetMonitor::useDeterministicHostSelection = false;
ReplicaSetMonitor::ReplicaSetMonitor(StringData name, const std::set<HostAndPort>& seeds)
: _state(boost::make_shared<SetState>(name, seeds)) {
LogstreamBuilder lsb = log();
lsb << "starting new replica set monitor for replica set " << name << " with seeds ";
for (std::set<HostAndPort>::const_iterator it = seeds.begin();
it != seeds.end(); ++it) {
if (it != seeds.begin())
lsb << ',';
lsb << *it;
}
}
HostAndPort ReplicaSetMonitor::getHostOrRefresh(const ReadPreferenceSetting& criteria) {
{
boost::mutex::scoped_lock lk(_state->mutex);
HostAndPort out = _state->getMatchingHost(criteria);
if (!out.empty())
return out;
}
{
Refresher refresher = startOrContinueRefresh();
HostAndPort out = refresher.refreshUntilMatches(criteria);
if (!out.empty() || refresher.startedNewScan())
return out;
}
// We didn't find any matching hosts and the scan we just finished may have stale data from
// before we joined. Therefore we should participate in a new scan to make sure all hosts
// are contacted at least once (possibly by other threads) before this function gives up.
return startOrContinueRefresh().refreshUntilMatches(criteria);
}
HostAndPort ReplicaSetMonitor::getMasterOrUassert() {
const ReadPreferenceSetting masterOnly(ReadPreference_PrimaryOnly, TagSet());
HostAndPort master = getHostOrRefresh(masterOnly);
uassert(10009, str::stream() << "ReplicaSetMonitor no master found for set: " << getName(),
!master.empty());
return master;
}
Refresher ReplicaSetMonitor::startOrContinueRefresh() {
boost::mutex::scoped_lock lk(_state->mutex);
Refresher out(_state);
DEV _state->checkInvariants();
return out;
}
void ReplicaSetMonitor::failedHost(const HostAndPort& host) {
boost::mutex::scoped_lock lk(_state->mutex);
Node* node = _state->findNode(host);
if (node)
node->markFailed();
DEV _state->checkInvariants();
}
bool ReplicaSetMonitor::isPrimary(const HostAndPort& host) const {
boost::mutex::scoped_lock lk(_state->mutex);
Node* node = _state->findNode(host);
return node ? node->isMaster : false;
}
bool ReplicaSetMonitor::isHostUp(const HostAndPort& host) const {
boost::mutex::scoped_lock lk(_state->mutex);
Node* node = _state->findNode(host);
return node ? node->isUp : false;
}
int ReplicaSetMonitor::getConsecutiveFailedScans() const {
boost::mutex::scoped_lock lk(_state->mutex);
return _state->consecutiveFailedScans;
}
std::string ReplicaSetMonitor::getName() const {
// name is const so don't need to lock
return _state->name;
}
std::string ReplicaSetMonitor::getServerAddress() const {
boost::mutex::scoped_lock lk(_state->mutex);
return _state->getServerAddress();
}
bool ReplicaSetMonitor::contains(const HostAndPort& host) const {
boost::mutex::scoped_lock lk(_state->mutex);
return _state->seedNodes.count(host);
}
void ReplicaSetMonitor::createIfNeeded(const string& name, const set<HostAndPort>& servers) {
LOG(3) << "ReplicaSetMonitor::createIfNeeded " << name;
scoped_lock lk(setsLock);
ReplicaSetMonitorPtr& m = sets[name];
if ( ! m )
m = boost::make_shared<ReplicaSetMonitor>( name , servers );
replicaSetMonitorWatcher.safeGo();
}
ReplicaSetMonitorPtr ReplicaSetMonitor::get(const std::string& name,
const bool createFromSeed) {
LOG(3) << "ReplicaSetMonitor::get " << name;
scoped_lock lk( setsLock );
StringMap<ReplicaSetMonitorPtr>::const_iterator i = sets.find( name );
if ( i != sets.end() ) {
return i->second;
}
if ( createFromSeed ) {
StringMap<set<HostAndPort> >::const_iterator j = seedServers.find( name );
if ( j != seedServers.end() ) {
LOG(4) << "Creating ReplicaSetMonitor from cached address";
ReplicaSetMonitorPtr& m = sets[name];
invariant( !m );
m.reset( new ReplicaSetMonitor( name, j->second ) );
replicaSetMonitorWatcher.safeGo();
return m;
}
}
return ReplicaSetMonitorPtr();
}
set<string> ReplicaSetMonitor::getAllTrackedSets() {
set<string> activeSets;
scoped_lock lk( setsLock );
for (StringMap<ReplicaSetMonitorPtr>::const_iterator it = sets.begin();
it != sets.end(); ++it)
{
activeSets.insert(it->first);
}
return activeSets;
}
void ReplicaSetMonitor::remove(const string& name, bool clearSeedCache) {
LOG(2) << "Removing ReplicaSetMonitor for " << name << " from replica set table"
<< (clearSeedCache ? " and the seed cache" : "");
scoped_lock lk( setsLock );
const StringMap<ReplicaSetMonitorPtr>::const_iterator setIt = sets.find(name);
if (setIt != sets.end()) {
if (!clearSeedCache) {
// Save list of current set members so that the monitor can be rebuilt if needed.
const ReplicaSetMonitorPtr& rsm = setIt->second;
boost::mutex::scoped_lock lk(rsm->_state->mutex);
seedServers[name] = rsm->_state->seedNodes;
}
sets.erase(setIt);
}
if ( clearSeedCache ) {
seedServers.erase( name );
}
// Kill all pooled ReplicaSetConnections for this set. They will not function correctly
// after we kill the ReplicaSetMonitor.
// TODO we may only need to do this if clearSeedCache is true.
pool.removeHost(name);
}
void ReplicaSetMonitor::setConfigChangeHook(ConfigChangeHook hook) {
massert(13610, "ConfigChangeHook already specified", !SetState::configChangeHook);
SetState::configChangeHook = hook;
}
// TODO move to correct order with non-statics before pushing
void ReplicaSetMonitor::appendInfo(BSONObjBuilder& bsonObjBuilder) const {
boost::mutex::scoped_lock lk(_state->mutex);
// NOTE: the format here must be consistent for backwards compatibility
BSONArrayBuilder hosts(bsonObjBuilder.subarrayStart("hosts"));
for (unsigned i = 0; i < _state->nodes.size(); i++) {
const Node& node = _state->nodes[i];
BSONObjBuilder builder;
builder.append("addr", node.host.toString());
builder.append("ok", node.isUp);
builder.append("ismaster", node.isMaster); // intentionally not camelCase
builder.append("hidden", false); // we don't keep hidden nodes in the set
builder.append("secondary", node.isUp && !node.isMaster);
builder.append("pingTimeMillis", int(node.latencyMicros / 1000));
if (!node.tags.isEmpty()) {
builder.append("tags", node.tags);
}
hosts.append(builder.obj());
}
hosts.done();
}
void ReplicaSetMonitor::cleanup() {
// Call cancel first, in case the RSMW was never started.
replicaSetMonitorWatcher.cancel();
replicaSetMonitorWatcher.stop();
replicaSetMonitorWatcher.wait();
scoped_lock lock(setsLock);
sets = StringMap<ReplicaSetMonitorPtr>();
seedServers = StringMap<set<HostAndPort> >();
}
Refresher::Refresher(const SetStatePtr& setState)
: _set(setState)
, _scan(setState->currentScan)
, _startedNewScan(false) {
if (_scan)
return; // participate in in-progress scan
LOG(2) << "Starting new refresh of replica set " << _set->name;
_scan = startNewScan(_set.get());
_set->currentScan = _scan;
_startedNewScan = true;
}
Refresher::NextStep Refresher::getNextStep() {
if (_scan != _set->currentScan)
return NextStep(NextStep::DONE); // No longer the current scan.
// Wait for all dispatched hosts to return before trying any fallback hosts.
if (_scan->hostsToScan.empty() && !_scan->waitingFor.empty())
return NextStep(NextStep::WAIT);
// If we haven't yet found a master, try contacting unconfirmed hosts
if (_scan->hostsToScan.empty() && !_scan->foundUpMaster) {
_scan->enqueAllUntriedHosts(_scan->possibleNodes, _set->rand);
_scan->possibleNodes.clear();
}
if (_scan->hostsToScan.empty()) {
// We've tried all hosts we can, so nothing more to do in this round.
if (!_scan->foundUpMaster) {
warning() << "No primary detected for set " << _set->name;
// Since we've talked to everyone we could but still didn't find a primary, we
// do the best we can, and assume all unconfirmedReplies are actually from nodes
// in the set (we've already confirmed that they think they are). This is
// important since it allows us to bootstrap to a usable state even if we are
// unable to talk to a master while starting up. As soon as we are able to
// contact a master, we will remove any nodes that it doesn't think are part of
// the set, undoing the damage we cause here.
// NOTE: we don't modify seedNodes or notify about set membership change in this
// case since it hasn't been confirmed by a master.
for (UnconfirmedReplies::iterator it = _scan->unconfirmedReplies.begin();
it != _scan->unconfirmedReplies.end(); ++it) {
_set->findOrCreateNode(it->host)->update(*it);
}
}
if (_scan->foundAnyUpNodes) {
_set->consecutiveFailedScans = 0;
}
else {
_set->consecutiveFailedScans++;
log() << "All nodes for set " << _set->name << " are down. "
<< "This has happened for " << _set->consecutiveFailedScans
<< " checks in a row. Polling will stop after "
<< maxConsecutiveFailedChecks - _set->consecutiveFailedScans
<< " more failed checks";
}
_set->currentScan.reset(); // Makes sure all other Refreshers in this round return DONE
return NextStep(NextStep::DONE);
}
// Pop and return the next hostToScan.
HostAndPort host = _scan->hostsToScan.front();
_scan->hostsToScan.pop_front();
_scan->waitingFor.insert(host);
_scan->triedHosts.insert(host);
return NextStep(NextStep::CONTACT_HOST, host);
}
void Refresher::receivedIsMaster(const HostAndPort& from,
int64_t latencyMicros,
const BSONObj& replyObj) {
// Be careful: all return paths must call either failedHost or cv.notify_all!
_scan->waitingFor.erase(from);
const IsMasterReply reply(from, latencyMicros, replyObj);
// Handle various failure cases
if (!reply.ok) {
failedHost(from);
return;
}
if (reply.setName != _set->name) {
warning() << "node: " << from
<< " isn't a part of set: " << _set->name
<< " ismaster: " << replyObj;
failedHost(from);
return;
}
if (reply.isMaster)
receivedIsMasterFromMaster(reply);
if (_scan->foundUpMaster) {
// We only update a Node if a master has confirmed it is in the set.
_set->updateNodeIfInNodes(reply);
}
else {
receivedIsMasterBeforeFoundMaster(reply);
_scan->unconfirmedReplies.push_back(reply);
}
// _set->nodes may still not have any nodes with isUp==true, but we have at least found a
// connectible host that is that claims to be in the set.
_scan->foundAnyUpNodes = true;
// TODO consider only notifying if we've updated a node or we've emptied waitingFor.
_set->cv.notify_all();
DEV _set->checkInvariants();
}
void Refresher::failedHost(const HostAndPort& host) {
_scan->waitingFor.erase(host);
// Failed hosts can't pass criteria, so the only way they'd effect the _refreshUntilMatches
// loop is if it was the last host we were waitingFor.
if (_scan->waitingFor.empty())
_set->cv.notify_all();
Node* node = _set->findNode(host);
if (node)
node->markFailed();
}
ScanStatePtr Refresher::startNewScan(const SetState* set) {
const ScanStatePtr scan = boost::make_shared<ScanState>();
// The heuristics we use in deciding the order to contact hosts are designed to find a
// master as quickly as possible. This is because we can't use any hosts we find until
// we either get the latest set of members from a master or talk to all possible hosts
// without finding a master.
// TODO It might make sense to check down nodes first if the last seen master is still
// marked as up.
int upNodes = 0;
for (Nodes::const_iterator it(set->nodes.begin()), end(set->nodes.end());
it != end; ++it) {
if (it->isUp) {
// scan the nodes we think are up first
scan->hostsToScan.push_front(it->host);
upNodes++;
}
else {
scan->hostsToScan.push_back(it->host);
}
}
// shuffle the queue, but keep "up" nodes at the front
std::random_shuffle(scan->hostsToScan.begin(),
scan->hostsToScan.begin() + upNodes,
set->rand);
std::random_shuffle(scan->hostsToScan.begin() + upNodes,
scan->hostsToScan.end(),
set->rand);
if (!set->lastSeenMaster.empty()) {
// move lastSeenMaster to front of queue
std::stable_partition(scan->hostsToScan.begin(),
scan->hostsToScan.end(),
hostIs(set->lastSeenMaster));
}
return scan;
}
void Refresher::receivedIsMasterFromMaster(const IsMasterReply& reply) {
invariant(reply.isMaster);
// Mark all nodes as not master. We will mark ourself as master before releasing the lock.
// NOTE: we use a "last-wins" policy if multiple hosts claim to be master.
for (size_t i = 0; i < _set->nodes.size(); i++) {
_set->nodes[i].isMaster = false;
}
// Check if the master agrees with our current list of nodes.
// REMINDER: both _set->nodes and reply.normalHosts are sorted.
if (_set->nodes.size() != reply.normalHosts.size() ||
!std::equal(_set->nodes.begin(), _set->nodes.end(),
reply.normalHosts.begin(),
hostsEqual)) {
LOG(2) << "Adjusting nodes in our view of replica set " << _set->name
<< " based on master reply: " << reply.raw;
// remove non-members from _set->nodes
_set->nodes.erase(std::remove_if(_set->nodes.begin(),
_set->nodes.end(),
hostNotIn(reply.normalHosts)),
_set->nodes.end());
// add new members to _set->nodes
for (std::set<HostAndPort>::const_iterator it = reply.normalHosts.begin();
it != reply.normalHosts.end(); ++it) {
_set->findOrCreateNode(*it);
}
// replace hostToScan queue with untried normal hosts. can both add and remove
// hosts from the queue.
_scan->hostsToScan.clear();
_scan->enqueAllUntriedHosts(reply.normalHosts, _set->rand);
if (!_scan->waitingFor.empty()) {
// make sure we don't wait for any hosts that aren't considered members
std::set<HostAndPort> newWaitingFor;
std::set_intersection(reply.normalHosts.begin(), reply.normalHosts.end(),
_scan->waitingFor.begin(), _scan->waitingFor.end(),
std::inserter(newWaitingFor, newWaitingFor.end()));
_scan->waitingFor.swap(newWaitingFor);
}
}
if (reply.normalHosts != _set->seedNodes) {
const string oldAddr = _set->getServerAddress();
_set->seedNodes = reply.normalHosts;
// LogLevel can be pretty low, since replica set reconfiguration should be pretty rare
// and we want to record our changes
log() << "changing hosts to " << _set->getServerAddress() << " from " << oldAddr;
if (SetState::configChangeHook) {
// call from a separate thread to avoid blocking and holding lock while potentially
// going over the network
boost::thread bg(SetState::configChangeHook, _set->name, _set->getServerAddress());
bg.detach();
}
}
// Update other nodes's information based on replies we've already seen
for (UnconfirmedReplies::iterator it = _scan->unconfirmedReplies.begin();
it != _scan->unconfirmedReplies.end(); ++it) {
// this ignores replies from hosts not in _set->nodes (as modified above)
_set->updateNodeIfInNodes(*it);
}
_scan->unconfirmedReplies.clear();
_scan->foundUpMaster = true;
_set->lastSeenMaster = reply.host;
}
void Refresher::receivedIsMasterBeforeFoundMaster(const IsMasterReply& reply) {
invariant(!reply.isMaster);
// This function doesn't alter _set at all. It only modifies the work queue in _scan.
// Add everyone this host claims is in the set to possibleNodes.
_scan->possibleNodes.insert(reply.normalHosts.begin(), reply.normalHosts.end());
// If this node thinks the primary is someone we haven't tried, make that the next
// hostToScan.
if (!reply.primary.empty() && !_scan->triedHosts.count(reply.primary)) {
std::deque<HostAndPort>::iterator it =
std::stable_partition(_scan->hostsToScan.begin(),
_scan->hostsToScan.end(),
hostIs(reply.primary));
if (it == _scan->hostsToScan.begin()) {
// reply.primary wasn't in hostsToScan
_scan->hostsToScan.push_front(reply.primary);
}
}
}
HostAndPort Refresher::_refreshUntilMatches(const ReadPreferenceSetting* criteria) {
boost::mutex::scoped_lock lk(_set->mutex);
while (true) {
if (criteria) {
HostAndPort out = _set->getMatchingHost(*criteria);
if (!out.empty())
return out;
}
const NextStep ns = getNextStep();
switch(ns.step) {
case NextStep::DONE:
DEV _set->checkInvariants();
// getNextStep may have updated nodes if no master was found.
return criteria ? _set->getMatchingHost(*criteria) : HostAndPort();
case NextStep::WAIT: // TODO consider treating as DONE for refreshAll
DEV _set->checkInvariants();
_set->cv.wait(lk);
continue;
case NextStep::CONTACT_HOST: {
BSONObj reply; // empty on error
int64_t pingMicros = 0;
DEV _set->checkInvariants();
lk.unlock(); // relocked after attempting to call isMaster
try {
ScopedDbConnection conn(ConnectionString(ns.host), socketTimeoutSecs);
bool ignoredOutParam = false;
Timer timer;
conn->isMaster(ignoredOutParam, &reply);
pingMicros = timer.micros();
conn.done(); // return to pool on success.
}
catch (...) {
reply = BSONObj(); // should be a no-op but want to be sure
}
lk.lock();
// Ignore the reply and return if we are no longer the current scan. This might
// happen if it was decided that the host we were contacting isn't part of the set.
if (_scan != _set->currentScan)
return criteria ? _set->getMatchingHost(*criteria) : HostAndPort();
if (reply.isEmpty())
failedHost(ns.host);
else
receivedIsMaster(ns.host, pingMicros, reply);
}
}
}
}
void IsMasterReply::parse(const BSONObj& obj) {
try {
raw = obj.getOwned(); // don't use obj again after this line
ok = raw["ok"].trueValue();
if (!ok)
return;
setName = raw["setName"].str();
hidden = raw["hidden"].trueValue();
secondary = raw["secondary"].trueValue();
// hidden nodes can't be master, even if they claim to be.
isMaster = !hidden && raw["ismaster"].trueValue();
const string primaryString = raw["primary"].str();
primary = primaryString.empty() ? HostAndPort() : HostAndPort(primaryString);
// both hosts and passives, but not arbiters, are considered "normal hosts"
normalHosts.clear();
BSONForEach(host, raw.getObjectField("hosts")) {
normalHosts.insert(HostAndPort(host.String()));
}
BSONForEach(host, raw.getObjectField("passives")) {
normalHosts.insert(HostAndPort(host.String()));
}
tags = raw.getObjectField("tags");
} catch (const std::exception& e) {
ok = false;
log() << "exception while parsing isMaster reply: " << e.what() << " " << obj;
}
}
const int64_t Node::unknownLatency = numeric_limits<int64_t>::max();
bool Node::matches(const ReadPreference& pref) const {
if (!isUp)
return false;
if (pref == ReadPreference_PrimaryOnly) {
return isMaster;
}
if (pref == ReadPreference_SecondaryOnly) {
if (isMaster)
return false;
}
return true;
}
bool Node::matches(const BSONObj& tag) const {
BSONForEach(tagCriteria, tag) {
if (this->tags[tagCriteria.fieldNameStringData()] != tagCriteria)
return false;
}
return true;
}
void Node::update(const IsMasterReply& reply) {
invariant(host == reply.host);
invariant(reply.ok);
LOG(3) << "Updating host " << host << " based on ismaster reply: " << reply.raw;
// Nodes that are hidden or neither master or secondary are considered down since we can't
// send any operations to them.
isUp = !reply.hidden && (reply.isMaster || reply.secondary);
isMaster = reply.isMaster;
// save a copy if unchanged
if (!tags.binaryEqual(reply.tags))
tags = reply.tags.getOwned();
if (reply.latencyMicros >= 0) { // TODO upper bound?
if (latencyMicros == unknownLatency) {
latencyMicros = reply.latencyMicros;
}
else {
// update latency with smoothed moving average (1/4th the delta)
latencyMicros += (reply.latencyMicros - latencyMicros) / 4;
}
}
}
ReplicaSetMonitor::ConfigChangeHook SetState::configChangeHook;
SetState::SetState(StringData name, const std::set<HostAndPort>& seedNodes)
: name(name.toString())
, consecutiveFailedScans(0)
, seedNodes(seedNodes)
, latencyThresholdMicros(serverGlobalParams.defaultLocalThresholdMillis * 1000)
, rand(int64_t(time(0)))
, roundRobin(0)
{
uassert(13642, "Replica set seed list can't be empty", !seedNodes.empty());
if (name.empty())
warning() << "Replica set name empty, first node: " << *(seedNodes.begin());
// This adds the seed hosts to nodes, but they aren't usable for anything except seeding a
// scan until we start a scan and either find a master or contact all hosts without finding
// one.
// WARNING: if seedNodes is ever changed to not imply sorted iteration, you will need to
// sort nodes after this loop.
for (std::set<HostAndPort>::const_iterator it = seedNodes.begin();
it != seedNodes.end(); ++it) {
nodes.push_back(Node(*it));
}
DEV checkInvariants();
}
HostAndPort SetState::getMatchingHost(const ReadPreferenceSetting& criteria) const {
switch (criteria.pref) {
// "Prefered" read preferences are defined in terms of other preferences
case ReadPreference_PrimaryPreferred: {
HostAndPort out = getMatchingHost(ReadPreferenceSetting(ReadPreference_PrimaryOnly,
criteria.tags));
// NOTE: the spec says we should use the primary even if tags don't match
if (!out.empty())
return out;
return getMatchingHost(ReadPreferenceSetting(ReadPreference_SecondaryOnly,
criteria.tags));
}
case ReadPreference_SecondaryPreferred: {
HostAndPort out =
getMatchingHost(ReadPreferenceSetting(ReadPreference_SecondaryOnly,
criteria.tags));
if (!out.empty())
return out;
// NOTE: the spec says we should use the primary even if tags don't match
return getMatchingHost(ReadPreferenceSetting(ReadPreference_PrimaryOnly,
criteria.tags));
}
case ReadPreference_PrimaryOnly: {
// NOTE: isMaster implies isUp
Nodes::const_iterator it = std::find_if(nodes.begin(), nodes.end(), isMaster);
if (it == nodes.end())
return HostAndPort();
return it->host;
}
// The difference between these is handled by Node::matches
case ReadPreference_SecondaryOnly:
case ReadPreference_Nearest: {
BSONForEach(tagElem, criteria.tags.getTagBSON()) {
uassert(16358, "Tags should be a BSON object", tagElem.isABSONObj());
BSONObj tag = tagElem.Obj();
std::vector<const Node*> matchingNodes;
for (size_t i = 0; i < nodes.size(); i++ ) {
if (nodes[i].matches(criteria.pref) && nodes[i].matches(tag)) {
matchingNodes.push_back(&nodes[i]);
}
}
// don't do more complicated selection if not needed
if (matchingNodes.empty()) continue;
if (matchingNodes.size() == 1) return matchingNodes.front()->host;
// order by latency and don't consider hosts further than a threshold from the
// closest.
std::sort(matchingNodes.begin(), matchingNodes.end(), compareLatencies);
for (size_t i = 1; i < matchingNodes.size(); i++ ) {
int64_t distance = matchingNodes[i]->latencyMicros
- matchingNodes[0]->latencyMicros;
if (distance >= latencyThresholdMicros) {
// this node and all remaining ones are too far away
matchingNodes.erase(matchingNodes.begin() + i, matchingNodes.end());
break;
}
}
// of the remaining nodes, pick one at random (or use round-robin)
if (ReplicaSetMonitor::useDeterministicHostSelection) {
// only in tests
return matchingNodes[roundRobin++ % matchingNodes.size()]->host;
}
else {
// normal case
return matchingNodes[rand.nextInt32(matchingNodes.size())]->host;
};
}
return HostAndPort();
}
default:
uassert( 16337, "Unknown read preference", false );
break;
}
}
Node* SetState::findNode(const HostAndPort& host) {
const Nodes::iterator it = std::lower_bound(nodes.begin(), nodes.end(), host, compareHosts);
if (it == nodes.end() || it->host != host)
return NULL;
return &(*it);
}
Node* SetState::findOrCreateNode(const HostAndPort& host) {
// This is insertion sort, but N is currently guaranteed to be <= 12 (although this class
// must function correctly even with more nodes). If we lift that restriction, we may need
// to consider alternate algorithms.
Nodes::iterator it = std::lower_bound(nodes.begin(), nodes.end(), host, compareHosts);
if (it == nodes.end() || it->host != host) {
LOG(2) << "Adding node " << host << " to our view of replica set " << name;
it = nodes.insert(it, Node(host));
}
return &(*it);
}
void SetState::updateNodeIfInNodes(const IsMasterReply& reply) {
Node* node = findNode(reply.host);
if (!node) {
LOG(2) << "Skipping application of ismaster reply from " << reply.host
<< " since it isn't a confirmed member of set " << name;
return;
}
node->update(reply);
}
std::string SetState::getServerAddress() const {
StringBuilder ss;
if (!name.empty())
ss << name << "/";
for (std::set<HostAndPort>::const_iterator it = seedNodes.begin();
it != seedNodes.end(); ++it) {
if (it != seedNodes.begin())
ss << ",";
it->append(ss);
}
return ss.str();
}
void SetState::checkInvariants() const {
bool foundMaster = false;
for (size_t i = 0; i < nodes.size(); i++) {
// no empty hosts
invariant(!nodes[i].host.empty());
if (nodes[i].isMaster) {
// masters must be up
invariant(nodes[i].isUp);
// at most one master
invariant(!foundMaster);
foundMaster = true;
// if we have a master it should be the same as lastSeenMaster
invariant(nodes[i].host == lastSeenMaster);
}
// should never end up with negative latencies
invariant(nodes[i].latencyMicros >= 0);
// nodes must be sorted by host with no-dupes
invariant(i == 0 || (nodes[i-1].host < nodes[i].host));
}
// nodes should be a (non-strict) superset of the seedNodes
invariant(std::includes(nodes.begin(), nodes.end(),
seedNodes.begin(), seedNodes.end(),
compareHosts));
if (currentScan) {
// hostsToScan can't have dups or hosts already in triedHosts.
std::set<HostAndPort> cantSee = currentScan->triedHosts;
for (std::deque<HostAndPort>::const_iterator it = currentScan->hostsToScan.begin();
it != currentScan->hostsToScan.end(); ++it) {
invariant(!cantSee.count(*it));
cantSee.insert(*it); // make sure we don't see this again
}
// We should only be waitingFor hosts that are in triedHosts
invariant(
std::includes(currentScan->triedHosts.begin(), currentScan->triedHosts.end(),
currentScan->waitingFor.begin(), currentScan->waitingFor.end()));
// We should only have unconfirmedReplies if we haven't found a master yet
invariant(!currentScan->foundUpMaster || currentScan->unconfirmedReplies.empty());
}
}
template <typename Container>
void ScanState::enqueAllUntriedHosts(const Container& container, PseudoRandom& rand) {
invariant(hostsToScan.empty()); // because we don't try to dedup hosts already in the queue.
// no std::copy_if before c++11
for (typename Container::const_iterator it(container.begin()), end(container.end());
it != end; ++it) {
if (!triedHosts.count(*it)) {
hostsToScan.push_back(*it);
}
}
std::random_shuffle(hostsToScan.begin(), hostsToScan.end(), rand);
}
}
|