File: conn.go

package info (click to toggle)
golang-github-go-zookeeper-zk 1.0.4-1
  • links: PTS, VCS
  • area: main
  • in suites: sid, trixie
  • size: 320 kB
  • sloc: makefile: 43
file content (1415 lines) | stat: -rw-r--r-- 39,154 bytes parent folder | download
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
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
// Package zk is a native Go client library for the ZooKeeper orchestration service.
package zk

/*
TODO:
* make sure a ping response comes back in a reasonable time

Possible watcher events:
* Event{Type: EventNotWatching, State: StateDisconnected, Path: path, Err: err}
*/

import (
	"context"
	"crypto/rand"
	"encoding/binary"
	"errors"
	"fmt"
	"io"
	"net"
	"strings"
	"sync"
	"sync/atomic"
	"time"
)

// ErrNoServer indicates that an operation cannot be completed
// because attempts to connect to all servers in the list failed.
var ErrNoServer = errors.New("zk: could not connect to a server")

// ErrInvalidPath indicates that an operation was being attempted on
// an invalid path. (e.g. empty path).
var ErrInvalidPath = errors.New("zk: invalid path")

// DefaultLogger uses the stdlib log package for logging.
var DefaultLogger Logger = defaultLogger{}

const (
	bufferSize      = 1536 * 1024
	eventChanSize   = 6
	sendChanSize    = 16
	protectedPrefix = "_c_"
)

type watchType int

const (
	watchTypeData watchType = iota
	watchTypeExist
	watchTypeChild
)

type watchPathType struct {
	path  string
	wType watchType
}

// Dialer is a function to be used to establish a connection to a single host.
type Dialer func(network, address string, timeout time.Duration) (net.Conn, error)

// Logger is an interface that can be implemented to provide custom log output.
type Logger interface {
	Printf(string, ...interface{})
}

type authCreds struct {
	scheme string
	auth   []byte
}

// Conn is the client connection and tracks all details for communication with the server.
type Conn struct {
	lastZxid         int64
	sessionID        int64
	state            State // must be 32-bit aligned
	xid              uint32
	sessionTimeoutMs int32 // session timeout in milliseconds
	passwd           []byte

	dialer         Dialer
	hostProvider   HostProvider
	serverMu       sync.Mutex // protects server
	server         string     // remember the address/port of the current server
	conn           net.Conn
	eventChan      chan Event
	eventCallback  EventCallback // may be nil
	shouldQuit     chan struct{}
	shouldQuitOnce sync.Once
	pingInterval   time.Duration
	recvTimeout    time.Duration
	connectTimeout time.Duration
	maxBufferSize  int

	creds   []authCreds
	credsMu sync.Mutex // protects server

	sendChan     chan *request
	requests     map[int32]*request // Xid -> pending request
	requestsLock sync.Mutex
	watchers     map[watchPathType][]chan Event
	watchersLock sync.Mutex
	closeChan    chan struct{} // channel to tell send loop stop

	// Debug (used by unit tests)
	reconnectLatch   chan struct{}
	setWatchLimit    int
	setWatchCallback func([]*setWatchesRequest)

	// Debug (for recurring re-auth hang)
	debugCloseRecvLoop bool
	resendZkAuthFn     func(context.Context, *Conn) error

	logger  Logger
	logInfo bool // true if information messages are logged; false if only errors are logged

	buf []byte
}

// connOption represents a connection option.
type connOption func(c *Conn)

type request struct {
	xid        int32
	opcode     int32
	pkt        interface{}
	recvStruct interface{}
	recvChan   chan response

	// Because sending and receiving happen in separate go routines, there's
	// a possible race condition when creating watches from outside the read
	// loop. We must ensure that a watcher gets added to the list synchronously
	// with the response from the server on any request that creates a watch.
	// In order to not hard code the watch logic for each opcode in the recv
	// loop the caller can use recvFunc to insert some synchronously code
	// after a response.
	recvFunc func(*request, *responseHeader, error)
}

type response struct {
	zxid int64
	err  error
}

// Event is an Znode event sent by the server.
// Refer to EventType for more details.
type Event struct {
	Type   EventType
	State  State
	Path   string // For non-session events, the path of the watched node.
	Err    error
	Server string // For connection events
}

// HostProvider is used to represent a set of hosts a ZooKeeper client should connect to.
// It is an analog of the Java equivalent:
// http://svn.apache.org/viewvc/zookeeper/trunk/src/java/main/org/apache/zookeeper/client/HostProvider.java?view=markup
type HostProvider interface {
	// Init is called first, with the servers specified in the connection string.
	Init(servers []string) error
	// Len returns the number of servers.
	Len() int
	// Next returns the next server to connect to. retryStart will be true if we've looped through
	// all known servers without Connected() being called.
	Next() (server string, retryStart bool)
	// Notify the HostProvider of a successful connection.
	Connected()
}

// ConnectWithDialer establishes a new connection to a pool of zookeeper servers
// using a custom Dialer. See Connect for further information about session timeout.
// This method is deprecated and provided for compatibility: use the WithDialer option instead.
func ConnectWithDialer(servers []string, sessionTimeout time.Duration, dialer Dialer) (*Conn, <-chan Event, error) {
	return Connect(servers, sessionTimeout, WithDialer(dialer))
}

// Connect establishes a new connection to a pool of zookeeper
// servers. The provided session timeout sets the amount of time for which
// a session is considered valid after losing connection to a server. Within
// the session timeout it's possible to reestablish a connection to a different
// server and keep the same session. This is means any ephemeral nodes and
// watches are maintained.
func Connect(servers []string, sessionTimeout time.Duration, options ...connOption) (*Conn, <-chan Event, error) {
	if len(servers) == 0 {
		return nil, nil, errors.New("zk: server list must not be empty")
	}

	srvs := FormatServers(servers)

	// Randomize the order of the servers to avoid creating hotspots
	stringShuffle(srvs)

	ec := make(chan Event, eventChanSize)
	conn := &Conn{
		dialer:         net.DialTimeout,
		hostProvider:   NewDNSHostProvider(),
		conn:           nil,
		state:          StateDisconnected,
		eventChan:      ec,
		shouldQuit:     make(chan struct{}),
		connectTimeout: 1 * time.Second,
		sendChan:       make(chan *request, sendChanSize),
		requests:       make(map[int32]*request),
		watchers:       make(map[watchPathType][]chan Event),
		passwd:         emptyPassword,
		logger:         DefaultLogger,
		logInfo:        true, // default is true for backwards compatability
		buf:            make([]byte, bufferSize),
		resendZkAuthFn: resendZkAuth,
	}

	// Set provided options.
	for _, option := range options {
		option(conn)
	}

	if err := conn.hostProvider.Init(srvs); err != nil {
		return nil, nil, err
	}

	conn.setTimeouts(int32(sessionTimeout / time.Millisecond))
	// TODO: This context should be passed in by the caller to be the connection lifecycle context.
	ctx := context.Background()

	go func() {
		conn.loop(ctx)
		conn.flushRequests(ErrClosing)
		conn.invalidateWatches(ErrClosing)
		close(conn.eventChan)
	}()
	return conn, ec, nil
}

// WithDialer returns a connection option specifying a non-default Dialer.
func WithDialer(dialer Dialer) connOption {
	return func(c *Conn) {
		c.dialer = dialer
	}
}

// WithHostProvider returns a connection option specifying a non-default HostProvider.
func WithHostProvider(hostProvider HostProvider) connOption {
	return func(c *Conn) {
		c.hostProvider = hostProvider
	}
}

// WithLogger returns a connection option specifying a non-default Logger.
func WithLogger(logger Logger) connOption {
	return func(c *Conn) {
		c.logger = logger
	}
}

// WithLogInfo returns a connection option specifying whether or not information messages
// should be logged.
func WithLogInfo(logInfo bool) connOption {
	return func(c *Conn) {
		c.logInfo = logInfo
	}
}

// EventCallback is a function that is called when an Event occurs.
type EventCallback func(Event)

// WithEventCallback returns a connection option that specifies an event
// callback.
// The callback must not block - doing so would delay the ZK go routines.
func WithEventCallback(cb EventCallback) connOption {
	return func(c *Conn) {
		c.eventCallback = cb
	}
}

// WithMaxBufferSize sets the maximum buffer size used to read and decode
// packets received from the Zookeeper server. The standard Zookeeper client for
// Java defaults to a limit of 1mb. For backwards compatibility, this Go client
// defaults to unbounded unless overridden via this option. A value that is zero
// or negative indicates that no limit is enforced.
//
// This is meant to prevent resource exhaustion in the face of potentially
// malicious data in ZK. It should generally match the server setting (which
// also defaults ot 1mb) so that clients and servers agree on the limits for
// things like the size of data in an individual znode and the total size of a
// transaction.
//
// For production systems, this should be set to a reasonable value (ideally
// that matches the server configuration). For ops tooling, it is handy to use a
// much larger limit, in order to do things like clean-up problematic state in
// the ZK tree. For example, if a single znode has a huge number of children, it
// is possible for the response to a "list children" operation to exceed this
// buffer size and cause errors in clients. The only way to subsequently clean
// up the tree (by removing superfluous children) is to use a client configured
// with a larger buffer size that can successfully query for all of the child
// names and then remove them. (Note there are other tools that can list all of
// the child names without an increased buffer size in the client, but they work
// by inspecting the servers' transaction logs to enumerate children instead of
// sending an online request to a server.
func WithMaxBufferSize(maxBufferSize int) connOption {
	return func(c *Conn) {
		c.maxBufferSize = maxBufferSize
	}
}

// WithMaxConnBufferSize sets maximum buffer size used to send and encode
// packets to Zookeeper server. The standard Zookeeper client for java defaults
// to a limit of 1mb. This option should be used for non-standard server setup
// where znode is bigger than default 1mb.
func WithMaxConnBufferSize(maxBufferSize int) connOption {
	return func(c *Conn) {
		c.buf = make([]byte, maxBufferSize)
	}
}

// Close will submit a close request with ZK and signal the connection to stop
// sending and receiving packets.
func (c *Conn) Close() {
	c.shouldQuitOnce.Do(func() {
		close(c.shouldQuit)

		select {
		case <-c.queueRequest(opClose, &closeRequest{}, &closeResponse{}, nil):
		case <-time.After(time.Second):
		}
	})
}

// State returns the current state of the connection.
func (c *Conn) State() State {
	return State(atomic.LoadInt32((*int32)(&c.state)))
}

// SessionID returns the current session id of the connection.
func (c *Conn) SessionID() int64 {
	return atomic.LoadInt64(&c.sessionID)
}

// SetLogger sets the logger to be used for printing errors.
// Logger is an interface provided by this package.
func (c *Conn) SetLogger(l Logger) {
	c.logger = l
}

func (c *Conn) setTimeouts(sessionTimeoutMs int32) {
	c.sessionTimeoutMs = sessionTimeoutMs
	sessionTimeout := time.Duration(sessionTimeoutMs) * time.Millisecond
	c.recvTimeout = sessionTimeout * 2 / 3
	c.pingInterval = c.recvTimeout / 2
}

func (c *Conn) setState(state State) {
	atomic.StoreInt32((*int32)(&c.state), int32(state))
	c.sendEvent(Event{Type: EventSession, State: state, Server: c.Server()})
}

func (c *Conn) sendEvent(evt Event) {
	if c.eventCallback != nil {
		c.eventCallback(evt)
	}

	select {
	case c.eventChan <- evt:
	default:
		// panic("zk: event channel full - it must be monitored and never allowed to be full")
	}
}

func (c *Conn) connect() error {
	var retryStart bool
	for {
		c.serverMu.Lock()
		c.server, retryStart = c.hostProvider.Next()
		c.serverMu.Unlock()

		c.setState(StateConnecting)

		if retryStart {
			c.flushUnsentRequests(ErrNoServer)
			select {
			case <-time.After(time.Second):
				// pass
			case <-c.shouldQuit:
				c.setState(StateDisconnected)
				c.flushUnsentRequests(ErrClosing)
				return ErrClosing
			}
		}

		zkConn, err := c.dialer("tcp", c.Server(), c.connectTimeout)
		if err == nil {
			c.conn = zkConn
			c.setState(StateConnected)
			if c.logInfo {
				c.logger.Printf("connected to %s", c.Server())
			}
			return nil
		}

		c.logger.Printf("failed to connect to %s: %v", c.Server(), err)
	}
}

func (c *Conn) sendRequest(
	opcode int32,
	req interface{},
	res interface{},
	recvFunc func(*request, *responseHeader, error),
) (
	<-chan response,
	error,
) {
	rq := &request{
		xid:        c.nextXid(),
		opcode:     opcode,
		pkt:        req,
		recvStruct: res,
		recvChan:   make(chan response, 1),
		recvFunc:   recvFunc,
	}

	if err := c.sendData(rq); err != nil {
		return nil, err
	}

	return rq.recvChan, nil
}

func (c *Conn) loop(ctx context.Context) {
	for {
		if err := c.connect(); err != nil {
			// c.Close() was called
			return
		}

		err := c.authenticate()
		switch {
		case err == ErrSessionExpired:
			c.logger.Printf("authentication failed: %s", err)
			c.invalidateWatches(err)
		case err != nil && c.conn != nil:
			c.logger.Printf("authentication failed: %s", err)
			c.conn.Close()
		case err == nil:
			if c.logInfo {
				c.logger.Printf("authenticated: id=%d, timeout=%d", c.SessionID(), c.sessionTimeoutMs)
			}
			c.hostProvider.Connected()        // mark success
			c.closeChan = make(chan struct{}) // channel to tell send loop stop

			var wg sync.WaitGroup

			wg.Add(1)
			go func() {
				defer c.conn.Close() // causes recv loop to EOF/exit
				defer wg.Done()

				if err := c.resendZkAuthFn(ctx, c); err != nil {
					c.logger.Printf("error in resending auth creds: %v", err)
					return
				}

				if err := c.sendLoop(); err != nil || c.logInfo {
					c.logger.Printf("send loop terminated: %v", err)
				}
			}()

			wg.Add(1)
			go func() {
				defer close(c.closeChan) // tell send loop to exit
				defer wg.Done()

				var err error
				if c.debugCloseRecvLoop {
					err = errors.New("DEBUG: close recv loop")
				} else {
					err = c.recvLoop(c.conn)
				}
				if err != io.EOF || c.logInfo {
					c.logger.Printf("recv loop terminated: %v", err)
				}
				if err == nil {
					panic("zk: recvLoop should never return nil error")
				}
			}()

			c.sendSetWatches()
			wg.Wait()
		}

		c.setState(StateDisconnected)

		select {
		case <-c.shouldQuit:
			c.flushRequests(ErrClosing)
			return
		default:
		}

		if err != ErrSessionExpired {
			err = ErrConnectionClosed
		}
		c.flushRequests(err)

		if c.reconnectLatch != nil {
			select {
			case <-c.shouldQuit:
				return
			case <-c.reconnectLatch:
			}
		}
	}
}

func (c *Conn) flushUnsentRequests(err error) {
	for {
		select {
		default:
			return
		case req := <-c.sendChan:
			req.recvChan <- response{-1, err}
		}
	}
}

// Send error to all pending requests and clear request map
func (c *Conn) flushRequests(err error) {
	c.requestsLock.Lock()
	for _, req := range c.requests {
		req.recvChan <- response{-1, err}
	}
	c.requests = make(map[int32]*request)
	c.requestsLock.Unlock()
}

// Send event to all interested watchers
func (c *Conn) notifyWatches(ev Event) {
	var wTypes []watchType
	switch ev.Type {
	case EventNodeCreated:
		wTypes = []watchType{watchTypeExist}
	case EventNodeDataChanged:
		wTypes = []watchType{watchTypeExist, watchTypeData}
	case EventNodeChildrenChanged:
		wTypes = []watchType{watchTypeChild}
	case EventNodeDeleted:
		wTypes = []watchType{watchTypeExist, watchTypeData, watchTypeChild}
	}
	c.watchersLock.Lock()
	defer c.watchersLock.Unlock()
	for _, t := range wTypes {
		wpt := watchPathType{ev.Path, t}
		if watchers := c.watchers[wpt]; len(watchers) > 0 {
			for _, ch := range watchers {
				ch <- ev
				close(ch)
			}
			delete(c.watchers, wpt)
		}
	}
}

// Send error to all watchers and clear watchers map
func (c *Conn) invalidateWatches(err error) {
	c.watchersLock.Lock()
	defer c.watchersLock.Unlock()

	if len(c.watchers) >= 0 {
		for pathType, watchers := range c.watchers {
			ev := Event{Type: EventNotWatching, State: StateDisconnected, Path: pathType.path, Err: err}
			c.sendEvent(ev) // also publish globally
			for _, ch := range watchers {
				ch <- ev
				close(ch)
			}
		}
		c.watchers = make(map[watchPathType][]chan Event)
	}
}

func (c *Conn) sendSetWatches() {
	c.watchersLock.Lock()
	defer c.watchersLock.Unlock()

	if len(c.watchers) == 0 {
		return
	}

	// NB: A ZK server, by default, rejects packets >1mb. So, if we have too
	// many watches to reset, we need to break this up into multiple packets
	// to avoid hitting that limit. Mirroring the Java client behavior: we are
	// conservative in that we limit requests to 128kb (since server limit is
	// is actually configurable and could conceivably be configured smaller
	// than default of 1mb).
	limit := 128 * 1024
	if c.setWatchLimit > 0 {
		limit = c.setWatchLimit
	}

	var reqs []*setWatchesRequest
	var req *setWatchesRequest
	var sizeSoFar int

	n := 0
	for pathType, watchers := range c.watchers {
		if len(watchers) == 0 {
			continue
		}
		addlLen := 4 + len(pathType.path)
		if req == nil || sizeSoFar+addlLen > limit {
			if req != nil {
				// add to set of requests that we'll send
				reqs = append(reqs, req)
			}
			sizeSoFar = 28 // fixed overhead of a set-watches packet
			req = &setWatchesRequest{
				RelativeZxid: c.lastZxid,
				DataWatches:  make([]string, 0),
				ExistWatches: make([]string, 0),
				ChildWatches: make([]string, 0),
			}
		}
		sizeSoFar += addlLen
		switch pathType.wType {
		case watchTypeData:
			req.DataWatches = append(req.DataWatches, pathType.path)
		case watchTypeExist:
			req.ExistWatches = append(req.ExistWatches, pathType.path)
		case watchTypeChild:
			req.ChildWatches = append(req.ChildWatches, pathType.path)
		}
		n++
	}
	if n == 0 {
		return
	}
	if req != nil { // don't forget any trailing packet we were building
		reqs = append(reqs, req)
	}

	if c.setWatchCallback != nil {
		c.setWatchCallback(reqs)
	}

	go func() {
		res := &setWatchesResponse{}
		// TODO: Pipeline these so queue all of them up before waiting on any
		// response. That will require some investigation to make sure there
		// aren't failure modes where a blocking write to the channel of requests
		// could hang indefinitely and cause this goroutine to leak...
		for _, req := range reqs {
			_, err := c.request(opSetWatches, req, res, nil)
			if err != nil {
				c.logger.Printf("Failed to set previous watches: %v", err)
				break
			}
		}
	}()
}

func (c *Conn) authenticate() error {
	buf := make([]byte, 256)

	// Encode and send a connect request.
	n, err := encodePacket(buf[4:], &connectRequest{
		ProtocolVersion: protocolVersion,
		LastZxidSeen:    c.lastZxid,
		TimeOut:         c.sessionTimeoutMs,
		SessionID:       c.SessionID(),
		Passwd:          c.passwd,
	})
	if err != nil {
		return err
	}

	binary.BigEndian.PutUint32(buf[:4], uint32(n))

	c.conn.SetWriteDeadline(time.Now().Add(c.recvTimeout * 10))
	_, err = c.conn.Write(buf[:n+4])
	c.conn.SetWriteDeadline(time.Time{})
	if err != nil {
		return err
	}

	// Receive and decode a connect response.
	c.conn.SetReadDeadline(time.Now().Add(c.recvTimeout * 10))
	_, err = io.ReadFull(c.conn, buf[:4])
	c.conn.SetReadDeadline(time.Time{})
	if err != nil {
		return err
	}

	blen := int(binary.BigEndian.Uint32(buf[:4]))
	if cap(buf) < blen {
		buf = make([]byte, blen)
	}

	_, err = io.ReadFull(c.conn, buf[:blen])
	if err != nil {
		return err
	}

	r := connectResponse{}
	_, err = decodePacket(buf[:blen], &r)
	if err != nil {
		return err
	}
	if r.SessionID == 0 {
		atomic.StoreInt64(&c.sessionID, int64(0))
		c.passwd = emptyPassword
		c.lastZxid = 0
		c.setState(StateExpired)
		return ErrSessionExpired
	}

	atomic.StoreInt64(&c.sessionID, r.SessionID)
	c.setTimeouts(r.TimeOut)
	c.passwd = r.Passwd
	c.setState(StateHasSession)

	return nil
}

func (c *Conn) sendData(req *request) error {
	header := &requestHeader{req.xid, req.opcode}
	n, err := encodePacket(c.buf[4:], header)
	if err != nil {
		req.recvChan <- response{-1, err}
		return nil
	}

	n2, err := encodePacket(c.buf[4+n:], req.pkt)
	if err != nil {
		req.recvChan <- response{-1, err}
		return nil
	}

	n += n2

	binary.BigEndian.PutUint32(c.buf[:4], uint32(n))

	c.requestsLock.Lock()
	select {
	case <-c.closeChan:
		req.recvChan <- response{-1, ErrConnectionClosed}
		c.requestsLock.Unlock()
		return ErrConnectionClosed
	default:
	}
	c.requests[req.xid] = req
	c.requestsLock.Unlock()

	c.conn.SetWriteDeadline(time.Now().Add(c.recvTimeout))
	_, err = c.conn.Write(c.buf[:n+4])
	c.conn.SetWriteDeadline(time.Time{})
	if err != nil {
		req.recvChan <- response{-1, err}
		c.conn.Close()
		return err
	}

	return nil
}

func (c *Conn) sendLoop() error {
	pingTicker := time.NewTicker(c.pingInterval)
	defer pingTicker.Stop()

	for {
		select {
		case req := <-c.sendChan:
			if err := c.sendData(req); err != nil {
				return err
			}
		case <-pingTicker.C:
			n, err := encodePacket(c.buf[4:], &requestHeader{Xid: -2, Opcode: opPing})
			if err != nil {
				panic("zk: opPing should never fail to serialize")
			}

			binary.BigEndian.PutUint32(c.buf[:4], uint32(n))

			c.conn.SetWriteDeadline(time.Now().Add(c.recvTimeout))
			_, err = c.conn.Write(c.buf[:n+4])
			c.conn.SetWriteDeadline(time.Time{})
			if err != nil {
				c.conn.Close()
				return err
			}
		case <-c.closeChan:
			return nil
		}
	}
}

func (c *Conn) recvLoop(conn net.Conn) error {
	sz := bufferSize
	if c.maxBufferSize > 0 && sz > c.maxBufferSize {
		sz = c.maxBufferSize
	}
	buf := make([]byte, sz)
	for {
		// package length
		if err := conn.SetReadDeadline(time.Now().Add(c.recvTimeout)); err != nil {
			c.logger.Printf("failed to set connection deadline: %v", err)
		}
		_, err := io.ReadFull(conn, buf[:4])
		if err != nil {
			return fmt.Errorf("failed to read from connection: %v", err)
		}

		blen := int(binary.BigEndian.Uint32(buf[:4]))
		if cap(buf) < blen {
			if c.maxBufferSize > 0 && blen > c.maxBufferSize {
				return fmt.Errorf("received packet from server with length %d, which exceeds max buffer size %d", blen, c.maxBufferSize)
			}
			buf = make([]byte, blen)
		}

		_, err = io.ReadFull(conn, buf[:blen])
		conn.SetReadDeadline(time.Time{})
		if err != nil {
			return err
		}

		res := responseHeader{}
		_, err = decodePacket(buf[:16], &res)
		if err != nil {
			return err
		}

		if res.Xid == -1 {
			res := &watcherEvent{}
			_, err = decodePacket(buf[16:blen], res)
			if err != nil {
				return err
			}
			ev := Event{
				Type:  res.Type,
				State: res.State,
				Path:  res.Path,
				Err:   nil,
			}
			c.sendEvent(ev)
			c.notifyWatches(ev)
		} else if res.Xid == -2 {
			// Ping response. Ignore.
		} else if res.Xid < 0 {
			c.logger.Printf("Xid < 0 (%d) but not ping or watcher event", res.Xid)
		} else {
			if res.Zxid > 0 {
				c.lastZxid = res.Zxid
			}

			c.requestsLock.Lock()
			req, ok := c.requests[res.Xid]
			if ok {
				delete(c.requests, res.Xid)
			}
			c.requestsLock.Unlock()

			if !ok {
				c.logger.Printf("Response for unknown request with xid %d", res.Xid)
			} else {
				if res.Err != 0 {
					err = res.Err.toError()
				} else {
					_, err = decodePacket(buf[16:blen], req.recvStruct)
				}
				if req.recvFunc != nil {
					req.recvFunc(req, &res, err)
				}
				req.recvChan <- response{res.Zxid, err}
				if req.opcode == opClose {
					return io.EOF
				}
			}
		}
	}
}

func (c *Conn) nextXid() int32 {
	return int32(atomic.AddUint32(&c.xid, 1) & 0x7fffffff)
}

func (c *Conn) addWatcher(path string, watchType watchType) <-chan Event {
	c.watchersLock.Lock()
	defer c.watchersLock.Unlock()

	ch := make(chan Event, 1)
	wpt := watchPathType{path, watchType}
	c.watchers[wpt] = append(c.watchers[wpt], ch)
	return ch
}

func (c *Conn) queueRequest(opcode int32, req interface{}, res interface{}, recvFunc func(*request, *responseHeader, error)) <-chan response {
	rq := &request{
		xid:        c.nextXid(),
		opcode:     opcode,
		pkt:        req,
		recvStruct: res,
		recvChan:   make(chan response, 2),
		recvFunc:   recvFunc,
	}

	switch opcode {
	case opClose:
		// always attempt to send close ops.
		select {
		case c.sendChan <- rq:
		case <-time.After(c.connectTimeout * 2):
			c.logger.Printf("gave up trying to send opClose to server")
			rq.recvChan <- response{-1, ErrConnectionClosed}
		}
	default:
		// otherwise avoid deadlocks for dumb clients who aren't aware that
		// the ZK connection is closed yet.
		select {
		case <-c.shouldQuit:
			rq.recvChan <- response{-1, ErrConnectionClosed}
		case c.sendChan <- rq:
			// check for a tie
			select {
			case <-c.shouldQuit:
				// maybe the caller gets this, maybe not- we tried.
				rq.recvChan <- response{-1, ErrConnectionClosed}
			default:
			}
		}
	}
	return rq.recvChan
}

func (c *Conn) request(opcode int32, req interface{}, res interface{}, recvFunc func(*request, *responseHeader, error)) (int64, error) {
	recv := c.queueRequest(opcode, req, res, recvFunc)
	select {
	case r := <-recv:
		return r.zxid, r.err
	case <-c.shouldQuit:
		// queueRequest() can be racy, double-check for the race here and avoid
		// a potential data-race. otherwise the client of this func may try to
		// access `res` fields concurrently w/ the async response processor.
		// NOTE: callers of this func should check for (at least) ErrConnectionClosed
		// and avoid accessing fields of the response object if such error is present.
		return -1, ErrConnectionClosed
	}
}

// AddAuth adds an authentication config to the connection.
func (c *Conn) AddAuth(scheme string, auth []byte) error {
	_, err := c.request(opSetAuth, &setAuthRequest{Type: 0, Scheme: scheme, Auth: auth}, &setAuthResponse{}, nil)

	if err != nil {
		return err
	}

	// Remember authdata so that it can be re-submitted on reconnect
	//
	// FIXME(prozlach): For now we treat "userfoo:passbar" and "userfoo:passbar2"
	// as two different entries, which will be re-submitted on reconnect. Some
	// research is needed on how ZK treats these cases and
	// then maybe switch to something like "map[username] = password" to allow
	// only single password for given user with users being unique.
	obj := authCreds{
		scheme: scheme,
		auth:   auth,
	}

	c.credsMu.Lock()
	c.creds = append(c.creds, obj)
	c.credsMu.Unlock()

	return nil
}

// Children returns the children of a znode.
func (c *Conn) Children(path string) ([]string, *Stat, error) {
	if err := validatePath(path, false); err != nil {
		return nil, nil, err
	}

	res := &getChildren2Response{}
	_, err := c.request(opGetChildren2, &getChildren2Request{Path: path, Watch: false}, res, nil)
	if err == ErrConnectionClosed {
		return nil, nil, err
	}
	return res.Children, &res.Stat, err
}

// ChildrenW returns the children of a znode and sets a watch.
func (c *Conn) ChildrenW(path string) ([]string, *Stat, <-chan Event, error) {
	if err := validatePath(path, false); err != nil {
		return nil, nil, nil, err
	}

	var ech <-chan Event
	res := &getChildren2Response{}
	_, err := c.request(opGetChildren2, &getChildren2Request{Path: path, Watch: true}, res, func(req *request, res *responseHeader, err error) {
		if err == nil {
			ech = c.addWatcher(path, watchTypeChild)
		}
	})
	if err != nil {
		return nil, nil, nil, err
	}
	return res.Children, &res.Stat, ech, err
}

// Get gets the contents of a znode.
func (c *Conn) Get(path string) ([]byte, *Stat, error) {
	if err := validatePath(path, false); err != nil {
		return nil, nil, err
	}

	res := &getDataResponse{}
	_, err := c.request(opGetData, &getDataRequest{Path: path, Watch: false}, res, nil)
	if err == ErrConnectionClosed {
		return nil, nil, err
	}
	return res.Data, &res.Stat, err
}

// GetW returns the contents of a znode and sets a watch
func (c *Conn) GetW(path string) ([]byte, *Stat, <-chan Event, error) {
	if err := validatePath(path, false); err != nil {
		return nil, nil, nil, err
	}

	var ech <-chan Event
	res := &getDataResponse{}
	_, err := c.request(opGetData, &getDataRequest{Path: path, Watch: true}, res, func(req *request, res *responseHeader, err error) {
		if err == nil {
			ech = c.addWatcher(path, watchTypeData)
		}
	})
	if err != nil {
		return nil, nil, nil, err
	}
	return res.Data, &res.Stat, ech, err
}

// Set updates the contents of a znode.
func (c *Conn) Set(path string, data []byte, version int32) (*Stat, error) {
	if err := validatePath(path, false); err != nil {
		return nil, err
	}

	res := &setDataResponse{}
	_, err := c.request(opSetData, &SetDataRequest{path, data, version}, res, nil)
	if err == ErrConnectionClosed {
		return nil, err
	}
	return &res.Stat, err
}

// Create creates a znode.
// The returned path is the new path assigned by the server, it may not be the
// same as the input, for example when creating a sequence znode the returned path
// will be the input path with a sequence number appended.
func (c *Conn) Create(path string, data []byte, flags int32, acl []ACL) (string, error) {
	createMode, err := parseCreateMode(flags)
	if err != nil {
		return "", err
	}

	if err := validatePath(path, createMode.isSequential); err != nil {
		return "", err
	}

	if createMode.isTTL {
		return "", fmt.Errorf("Create with TTL flag disallowed: %w", ErrInvalidFlags)
	}

	res := &createResponse{}
	_, err = c.request(opCreate, &CreateRequest{path, data, acl, createMode.flag}, res, nil)
	if err == ErrConnectionClosed {
		return "", err
	}
	return res.Path, err
}

// CreateContainer creates a container znode and returns the path.
//
// Containers cannot be ephemeral or sequential, or have TTLs.
// Ensure that we reject flags for TTL, Sequence, and Ephemeral.
func (c *Conn) CreateContainer(path string, data []byte, flag int32, acl []ACL) (string, error) {
	createMode, err := parseCreateMode(flag)
	if err != nil {
		return "", err
	}

	if err := validatePath(path, createMode.isSequential); err != nil {
		return "", err
	}

	if !createMode.isContainer {
		return "", fmt.Errorf("CreateContainer requires container flag: %w", ErrInvalidFlags)
	}

	res := &createResponse{}
	_, err = c.request(opCreateContainer, &CreateRequest{path, data, acl, createMode.flag}, res, nil)
	return res.Path, err
}

// CreateTTL creates a TTL znode, which will be automatically deleted by server after the TTL.
func (c *Conn) CreateTTL(path string, data []byte, flag int32, acl []ACL, ttl time.Duration) (string, error) {
	createMode, err := parseCreateMode(flag)
	if err != nil {
		return "", err
	}

	if err := validatePath(path, createMode.isSequential); err != nil {
		return "", err
	}

	if !createMode.isTTL {
		return "", fmt.Errorf("CreateTTL requires TTL flag: %w", ErrInvalidFlags)
	}

	res := &createResponse{}
	_, err = c.request(opCreateTTL, &CreateTTLRequest{path, data, acl, createMode.flag, ttl.Milliseconds()}, res, nil)
	return res.Path, err
}

// CreateProtectedEphemeralSequential fixes a race condition if the server crashes
// after it creates the node. On reconnect the session may still be valid so the
// ephemeral node still exists. Therefore, on reconnect we need to check if a node
// with a GUID generated on create exists.
func (c *Conn) CreateProtectedEphemeralSequential(path string, data []byte, acl []ACL) (string, error) {
	if err := validatePath(path, true); err != nil {
		return "", err
	}

	var guid [16]byte
	_, err := io.ReadFull(rand.Reader, guid[:16])
	if err != nil {
		return "", err
	}
	guidStr := fmt.Sprintf("%x", guid)

	parts := strings.Split(path, "/")
	parts[len(parts)-1] = fmt.Sprintf("%s%s-%s", protectedPrefix, guidStr, parts[len(parts)-1])
	rootPath := strings.Join(parts[:len(parts)-1], "/")
	protectedPath := strings.Join(parts, "/")

	var newPath string
	for i := 0; i < 3; i++ {
		newPath, err = c.Create(protectedPath, data, FlagEphemeral|FlagSequence, acl)
		switch err {
		case ErrSessionExpired:
			// No need to search for the node since it can't exist. Just try again.
		case ErrConnectionClosed:
			children, _, err := c.Children(rootPath)
			if err != nil {
				return "", err
			}
			for _, p := range children {
				parts := strings.Split(p, "/")
				if pth := parts[len(parts)-1]; strings.HasPrefix(pth, protectedPrefix) {
					if g := pth[len(protectedPrefix) : len(protectedPrefix)+32]; g == guidStr {
						return rootPath + "/" + p, nil
					}
				}
			}
		case nil:
			return newPath, nil
		default:
			return "", err
		}
	}
	return "", err
}

// Delete deletes a znode.
func (c *Conn) Delete(path string, version int32) error {
	if err := validatePath(path, false); err != nil {
		return err
	}

	_, err := c.request(opDelete, &DeleteRequest{path, version}, &deleteResponse{}, nil)
	return err
}

// Exists tells the existence of a znode.
func (c *Conn) Exists(path string) (bool, *Stat, error) {
	if err := validatePath(path, false); err != nil {
		return false, nil, err
	}

	res := &existsResponse{}
	_, err := c.request(opExists, &existsRequest{Path: path, Watch: false}, res, nil)
	if err == ErrConnectionClosed {
		return false, nil, err
	}
	exists := true
	if err == ErrNoNode {
		exists = false
		err = nil
	}
	return exists, &res.Stat, err
}

// ExistsW tells the existence of a znode and sets a watch.
func (c *Conn) ExistsW(path string) (bool, *Stat, <-chan Event, error) {
	if err := validatePath(path, false); err != nil {
		return false, nil, nil, err
	}

	var ech <-chan Event
	res := &existsResponse{}
	_, err := c.request(opExists, &existsRequest{Path: path, Watch: true}, res, func(req *request, res *responseHeader, err error) {
		if err == nil {
			ech = c.addWatcher(path, watchTypeData)
		} else if err == ErrNoNode {
			ech = c.addWatcher(path, watchTypeExist)
		}
	})
	exists := true
	if err == ErrNoNode {
		exists = false
		err = nil
	}
	if err != nil {
		return false, nil, nil, err
	}
	return exists, &res.Stat, ech, err
}

// GetACL gets the ACLs of a znode.
func (c *Conn) GetACL(path string) ([]ACL, *Stat, error) {
	if err := validatePath(path, false); err != nil {
		return nil, nil, err
	}

	res := &getAclResponse{}
	_, err := c.request(opGetAcl, &getAclRequest{Path: path}, res, nil)
	if err == ErrConnectionClosed {
		return nil, nil, err
	}
	return res.Acl, &res.Stat, err
}

// SetACL updates the ACLs of a znode.
func (c *Conn) SetACL(path string, acl []ACL, version int32) (*Stat, error) {
	if err := validatePath(path, false); err != nil {
		return nil, err
	}

	res := &setAclResponse{}
	_, err := c.request(opSetAcl, &setAclRequest{Path: path, Acl: acl, Version: version}, res, nil)
	if err == ErrConnectionClosed {
		return nil, err
	}
	return &res.Stat, err
}

// Sync flushes the channel between process and the leader of a given znode,
// you may need it if you want identical views of ZooKeeper data for 2 client instances.
// Please refer to the "Consistency Guarantees" section of ZK document for more details.
func (c *Conn) Sync(path string) (string, error) {
	if err := validatePath(path, false); err != nil {
		return "", err
	}

	res := &syncResponse{}
	_, err := c.request(opSync, &syncRequest{Path: path}, res, nil)
	if err == ErrConnectionClosed {
		return "", err
	}
	return res.Path, err
}

// MultiResponse is the result of a Multi call.
type MultiResponse struct {
	Stat   *Stat
	String string
	Error  error
}

// Multi executes multiple ZooKeeper operations or none of them. The provided
// ops must be one of *CreateRequest, *DeleteRequest, *SetDataRequest, or
// *CheckVersionRequest.
func (c *Conn) Multi(ops ...interface{}) ([]MultiResponse, error) {
	req := &multiRequest{
		Ops:        make([]multiRequestOp, 0, len(ops)),
		DoneHeader: multiHeader{Type: -1, Done: true, Err: -1},
	}
	for _, op := range ops {
		var opCode int32
		switch op.(type) {
		case *CreateRequest:
			opCode = opCreate
		case *SetDataRequest:
			opCode = opSetData
		case *DeleteRequest:
			opCode = opDelete
		case *CheckVersionRequest:
			opCode = opCheck
		default:
			return nil, fmt.Errorf("unknown operation type %T", op)
		}
		req.Ops = append(req.Ops, multiRequestOp{multiHeader{opCode, false, -1}, op})
	}
	res := &multiResponse{}
	_, err := c.request(opMulti, req, res, nil)
	if err == ErrConnectionClosed {
		return nil, err
	}
	mr := make([]MultiResponse, len(res.Ops))
	for i, op := range res.Ops {
		mr[i] = MultiResponse{Stat: op.Stat, String: op.String, Error: op.Err.toError()}
	}
	return mr, err
}

// IncrementalReconfig is the zookeeper reconfiguration api that allows adding and removing servers
// by lists of members. For more info refer to the ZK documentation.
//
// An optional version allows for conditional reconfigurations, -1 ignores the condition.
//
// Returns the new configuration znode stat.
func (c *Conn) IncrementalReconfig(joining, leaving []string, version int64) (*Stat, error) {
	// TODO: validate the shape of the member string to give early feedback.
	request := &reconfigRequest{
		JoiningServers: []byte(strings.Join(joining, ",")),
		LeavingServers: []byte(strings.Join(leaving, ",")),
		CurConfigId:    version,
	}

	return c.internalReconfig(request)
}

// Reconfig is the non-incremental update functionality for Zookeeper where the list provided
// is the entire new member list. For more info refer to the ZK documentation.
//
// An optional version allows for conditional reconfigurations, -1 ignores the condition.
//
// Returns the new configuration znode stat.
func (c *Conn) Reconfig(members []string, version int64) (*Stat, error) {
	request := &reconfigRequest{
		NewMembers:  []byte(strings.Join(members, ",")),
		CurConfigId: version,
	}

	return c.internalReconfig(request)
}

func (c *Conn) internalReconfig(request *reconfigRequest) (*Stat, error) {
	response := &reconfigReponse{}
	_, err := c.request(opReconfig, request, response, nil)
	return &response.Stat, err
}

// Server returns the current or last-connected server name.
func (c *Conn) Server() string {
	c.serverMu.Lock()
	defer c.serverMu.Unlock()
	return c.server
}

func resendZkAuth(ctx context.Context, c *Conn) error {
	shouldCancel := func() bool {
		select {
		case <-c.shouldQuit:
			return true
		case <-c.closeChan:
			return true
		default:
			return false
		}
	}

	c.credsMu.Lock()
	defer c.credsMu.Unlock()

	if c.logInfo {
		c.logger.Printf("re-submitting `%d` credentials after reconnect", len(c.creds))
	}

	for _, cred := range c.creds {
		// return early before attempting to send request.
		if shouldCancel() {
			return nil
		}
		// do not use the public API for auth since it depends on the send/recv loops
		// that are waiting for this to return
		resChan, err := c.sendRequest(
			opSetAuth,
			&setAuthRequest{Type: 0,
				Scheme: cred.scheme,
				Auth:   cred.auth,
			},
			&setAuthResponse{},
			nil, /* recvFunc*/
		)
		if err != nil {
			return fmt.Errorf("failed to send auth request: %v", err)
		}

		var res response
		select {
		case res = <-resChan:
		case <-c.closeChan:
			c.logger.Printf("recv closed, cancel re-submitting credentials")
			return nil
		case <-c.shouldQuit:
			c.logger.Printf("should quit, cancel re-submitting credentials")
			return nil
		case <-ctx.Done():
			return ctx.Err()
		}
		if res.err != nil {
			return fmt.Errorf("failed connection setAuth request: %v", res.err)
		}
	}

	return nil
}