forked from hashicorp/consul
-
Notifications
You must be signed in to change notification settings - Fork 0
/
leader.go
588 lines (534 loc) · 17 KB
/
leader.go
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
package consul
import (
"fmt"
"net"
"strconv"
"strings"
"time"
"github.com/armon/go-metrics"
"github.com/hashicorp/consul/consul/structs"
"github.com/hashicorp/raft"
"github.com/hashicorp/serf/serf"
)
const (
SerfCheckID = "serfHealth"
SerfCheckName = "Serf Health Status"
SerfCheckAliveOutput = "Agent alive and reachable"
SerfCheckFailedOutput = "Agent not live or unreachable"
ConsulServiceID = "consul"
ConsulServiceName = "consul"
newLeaderEvent = "consul:new-leader"
)
// monitorLeadership is used to monitor if we acquire or lose our role
// as the leader in the Raft cluster. There is some work the leader is
// expected to do, so we must react to changes
func (s *Server) monitorLeadership() {
leaderCh := s.raft.LeaderCh()
var stopCh chan struct{}
for {
select {
case isLeader := <-leaderCh:
if isLeader {
stopCh = make(chan struct{})
go s.leaderLoop(stopCh)
s.logger.Printf("[INFO] consul: cluster leadership acquired")
} else if stopCh != nil {
close(stopCh)
stopCh = nil
s.logger.Printf("[INFO] consul: cluster leadership lost")
}
case <-s.shutdownCh:
return
}
}
}
// leaderLoop runs as long as we are the leader to run various
// maintenance activities
func (s *Server) leaderLoop(stopCh chan struct{}) {
// Ensure we revoke leadership on stepdown
defer s.revokeLeadership()
// Fire a user event indicating a new leader
payload := []byte(s.config.NodeName)
if err := s.serfLAN.UserEvent(newLeaderEvent, payload, false); err != nil {
s.logger.Printf("[WARN] consul: failed to broadcast new leader event: %v", err)
}
// Reconcile channel is only used once initial reconcile
// has succeeded
var reconcileCh chan serf.Member
establishedLeader := false
RECONCILE:
// Setup a reconciliation timer
reconcileCh = nil
interval := time.After(s.config.ReconcileInterval)
// Apply a raft barrier to ensure our FSM is caught up
start := time.Now()
barrier := s.raft.Barrier(0)
if err := barrier.Error(); err != nil {
s.logger.Printf("[ERR] consul: failed to wait for barrier: %v", err)
goto WAIT
}
metrics.MeasureSince([]string{"consul", "leader", "barrier"}, start)
// Check if we need to handle initial leadership actions
if !establishedLeader {
if err := s.establishLeadership(); err != nil {
s.logger.Printf("[ERR] consul: failed to establish leadership: %v",
err)
goto WAIT
}
establishedLeader = true
}
// Reconcile any missing data
if err := s.reconcile(); err != nil {
s.logger.Printf("[ERR] consul: failed to reconcile: %v", err)
goto WAIT
}
// Initial reconcile worked, now we can process the channel
// updates
reconcileCh = s.reconcileCh
WAIT:
// Periodically reconcile as long as we are the leader,
// or when Serf events arrive
for {
select {
case <-stopCh:
return
case <-s.shutdownCh:
return
case <-interval:
goto RECONCILE
case member := <-reconcileCh:
s.reconcileMember(member)
case index := <-s.tombstoneGC.ExpireCh():
go s.reapTombstones(index)
}
}
}
// establishLeadership is invoked once we become leader and are able
// to invoke an initial barrier. The barrier is used to ensure any
// previously inflight transactions have been committed and that our
// state is up-to-date.
func (s *Server) establishLeadership() error {
// Hint the tombstone expiration timer. When we freshly establish leadership
// we become the authoritative timer, and so we need to start the clock
// on any pending GC events.
s.tombstoneGC.SetEnabled(true)
lastIndex := s.raft.LastIndex()
s.tombstoneGC.Hint(lastIndex)
s.logger.Printf("[DEBUG] consul: reset tombstone GC to index %d", lastIndex)
// Setup ACLs if we are the leader and need to
if err := s.initializeACL(); err != nil {
s.logger.Printf("[ERR] consul: ACL initialization failed: %v", err)
return err
}
// Setup the session timers. This is done both when starting up or when
// a leader fail over happens. Since the timers are maintained by the leader
// node along, effectively this means all the timers are renewed at the
// time of failover. The TTL contract is that the session will not be expired
// before the TTL, so expiring it later is allowable.
//
// This MUST be done after the initial barrier to ensure the latest Sessions
// are available to be initialized. Otherwise initialization may use stale
// data.
if err := s.initializeSessionTimers(); err != nil {
s.logger.Printf("[ERR] consul: Session Timers initialization failed: %v",
err)
return err
}
return nil
}
// revokeLeadership is invoked once we step down as leader.
// This is used to cleanup any state that may be specific to a leader.
func (s *Server) revokeLeadership() error {
// Disable the tombstone GC, since it is only useful as a leader
s.tombstoneGC.SetEnabled(false)
// Clear the session timers on either shutdown or step down, since we
// are no longer responsible for session expirations.
if err := s.clearAllSessionTimers(); err != nil {
s.logger.Printf("[ERR] consul: Clearing session timers failed: %v", err)
return err
}
return nil
}
// initializeACL is used to setup the ACLs if we are the leader
// and need to do this.
func (s *Server) initializeACL() error {
// Bail if not configured or we are not authoritative
authDC := s.config.ACLDatacenter
if len(authDC) == 0 || authDC != s.config.Datacenter {
return nil
}
// Purge the cache, since it could've changed while we
// were not the leader
s.aclAuthCache.Purge()
// Look for the anonymous token
state := s.fsm.State()
_, acl, err := state.ACLGet(anonymousToken)
if err != nil {
return fmt.Errorf("failed to get anonymous token: %v", err)
}
// Create anonymous token if missing
if acl == nil {
req := structs.ACLRequest{
Datacenter: authDC,
Op: structs.ACLSet,
ACL: structs.ACL{
ID: anonymousToken,
Name: "Anonymous Token",
Type: structs.ACLTypeClient,
},
}
_, err := s.raftApply(structs.ACLRequestType, &req)
if err != nil {
return fmt.Errorf("failed to create anonymous token: %v", err)
}
}
// Check for configured master token
master := s.config.ACLMasterToken
if len(master) == 0 {
return nil
}
// Look for the master token
_, acl, err = state.ACLGet(master)
if err != nil {
return fmt.Errorf("failed to get master token: %v", err)
}
if acl == nil {
req := structs.ACLRequest{
Datacenter: authDC,
Op: structs.ACLSet,
ACL: structs.ACL{
ID: master,
Name: "Master Token",
Type: structs.ACLTypeManagement,
},
}
_, err := s.raftApply(structs.ACLRequestType, &req)
if err != nil {
return fmt.Errorf("failed to create master token: %v", err)
}
}
return nil
}
// reconcile is used to reconcile the differences between Serf
// membership and what is reflected in our strongly consistent store.
// Mainly we need to ensure all live nodes are registered, all failed
// nodes are marked as such, and all left nodes are de-registered.
func (s *Server) reconcile() (err error) {
defer metrics.MeasureSince([]string{"consul", "leader", "reconcile"}, time.Now())
members := s.serfLAN.Members()
knownMembers := make(map[string]struct{})
for _, member := range members {
if err := s.reconcileMember(member); err != nil {
return err
}
knownMembers[member.Name] = struct{}{}
}
// Reconcile any members that have been reaped while we were not the leader
return s.reconcileReaped(knownMembers)
}
// reconcileReaped is used to reconcile nodes that have failed and been reaped
// from Serf but remain in the catalog. This is done by looking for SerfCheckID
// in a critical state that does not correspond to a known Serf member. We generate
// a "reap" event to cause the node to be cleaned up.
func (s *Server) reconcileReaped(known map[string]struct{}) error {
state := s.fsm.State()
_, checks, err := state.ChecksInState(structs.HealthAny)
if err != nil {
return err
}
for _, check := range checks {
// Ignore any non serf checks
if check.CheckID != SerfCheckID {
continue
}
// Check if this node is "known" by serf
if _, ok := known[check.Node]; ok {
continue
}
// Create a fake member
member := serf.Member{
Name: check.Node,
Tags: map[string]string{
"dc": s.config.Datacenter,
"role": "node",
},
}
// Get the node services, look for ConsulServiceID
_, services, err := state.NodeServices(check.Node)
if err != nil {
return err
}
serverPort := 0
for _, service := range services.Services {
if service.ID == ConsulServiceID {
serverPort = service.Port
break
}
}
// Create the appropriate tags if this was a server node
if serverPort > 0 {
member.Tags["role"] = "consul"
member.Tags["port"] = strconv.FormatUint(uint64(serverPort), 10)
}
// Attempt to reap this member
if err := s.handleReapMember(member); err != nil {
return err
}
}
return nil
}
// reconcileMember is used to do an async reconcile of a single
// serf member
func (s *Server) reconcileMember(member serf.Member) error {
// Check if this is a member we should handle
if !s.shouldHandleMember(member) {
s.logger.Printf("[WARN] consul: skipping reconcile of node %v", member)
return nil
}
defer metrics.MeasureSince([]string{"consul", "leader", "reconcileMember"}, time.Now())
var err error
switch member.Status {
case serf.StatusAlive:
err = s.handleAliveMember(member)
case serf.StatusFailed:
err = s.handleFailedMember(member)
case serf.StatusLeft:
err = s.handleLeftMember(member)
case StatusReap:
err = s.handleReapMember(member)
}
if err != nil {
s.logger.Printf("[ERR] consul: failed to reconcile member: %v: %v",
member, err)
// Permission denied should not bubble up
if strings.Contains(err.Error(), permissionDenied) {
return nil
}
return err
}
return nil
}
// shouldHandleMember checks if this is a Consul pool member
func (s *Server) shouldHandleMember(member serf.Member) bool {
if valid, dc := isConsulNode(member); valid && dc == s.config.Datacenter {
return true
}
if valid, parts := isConsulServer(member); valid && parts.Datacenter == s.config.Datacenter {
return true
}
return false
}
// handleAliveMember is used to ensure the node
// is registered, with a passing health check.
func (s *Server) handleAliveMember(member serf.Member) error {
// Register consul service if a server
var service *structs.NodeService
if valid, parts := isConsulServer(member); valid {
service = &structs.NodeService{
ID: ConsulServiceID,
Service: ConsulServiceName,
Port: parts.Port,
}
// Attempt to join the consul server
if err := s.joinConsulServer(member, parts); err != nil {
return err
}
}
// Check if the node exists
state := s.fsm.State()
_, node, err := state.GetNode(member.Name)
if err != nil {
return err
}
if node != nil && node.Address == member.Addr.String() {
// Check if the associated service is available
if service != nil {
match := false
_, services, err := state.NodeServices(member.Name)
if err != nil {
return err
}
if services != nil {
for id, _ := range services.Services {
if id == service.ID {
match = true
}
}
}
if !match {
goto AFTER_CHECK
}
}
// Check if the serfCheck is in the passing state
_, checks, err := state.NodeChecks(member.Name)
if err != nil {
return err
}
for _, check := range checks {
if check.CheckID == SerfCheckID && check.Status == structs.HealthPassing {
return nil
}
}
}
AFTER_CHECK:
s.logger.Printf("[INFO] consul: member '%s' joined, marking health alive", member.Name)
// Register with the catalog
req := structs.RegisterRequest{
Datacenter: s.config.Datacenter,
Node: member.Name,
Address: member.Addr.String(),
Service: service,
Check: &structs.HealthCheck{
Node: member.Name,
CheckID: SerfCheckID,
Name: SerfCheckName,
Status: structs.HealthPassing,
Output: SerfCheckAliveOutput,
},
WriteRequest: structs.WriteRequest{Token: s.config.ACLToken},
}
var out struct{}
return s.endpoints.Catalog.Register(&req, &out)
}
// handleFailedMember is used to mark the node's status
// as being critical, along with all checks as unknown.
func (s *Server) handleFailedMember(member serf.Member) error {
// Check if the node exists
state := s.fsm.State()
_, node, err := state.GetNode(member.Name)
if err != nil {
return err
}
if node != nil && node.Address == member.Addr.String() {
// Check if the serfCheck is in the critical state
_, checks, err := state.NodeChecks(member.Name)
if err != nil {
return err
}
for _, check := range checks {
if check.CheckID == SerfCheckID && check.Status == structs.HealthCritical {
return nil
}
}
}
s.logger.Printf("[INFO] consul: member '%s' failed, marking health critical", member.Name)
// Register with the catalog
req := structs.RegisterRequest{
Datacenter: s.config.Datacenter,
Node: member.Name,
Address: member.Addr.String(),
Check: &structs.HealthCheck{
Node: member.Name,
CheckID: SerfCheckID,
Name: SerfCheckName,
Status: structs.HealthCritical,
Output: SerfCheckFailedOutput,
},
WriteRequest: structs.WriteRequest{Token: s.config.ACLToken},
}
var out struct{}
return s.endpoints.Catalog.Register(&req, &out)
}
// handleLeftMember is used to handle members that gracefully
// left. They are deregistered if necessary.
func (s *Server) handleLeftMember(member serf.Member) error {
return s.handleDeregisterMember("left", member)
}
// handleReapMember is used to handle members that have been
// reaped after a prolonged failure. They are deregistered.
func (s *Server) handleReapMember(member serf.Member) error {
return s.handleDeregisterMember("reaped", member)
}
// handleDeregisterMember is used to deregister a member of a given reason
func (s *Server) handleDeregisterMember(reason string, member serf.Member) error {
// Do not deregister ourself. This can only happen if the current leader
// is leaving. Instead, we should allow a follower to take-over and
// deregister us later.
if member.Name == s.config.NodeName {
s.logger.Printf("[WARN] consul: deregistering self (%s) should be done by follower", s.config.NodeName)
return nil
}
// Remove from Raft peers if this was a server
if valid, parts := isConsulServer(member); valid {
if err := s.removeConsulServer(member, parts.Port); err != nil {
return err
}
}
// Check if the node does not exist
state := s.fsm.State()
_, node, err := state.GetNode(member.Name)
if err != nil {
return err
}
if node == nil {
return nil
}
// Deregister the node
s.logger.Printf("[INFO] consul: member '%s' %s, deregistering", member.Name, reason)
req := structs.DeregisterRequest{
Datacenter: s.config.Datacenter,
Node: member.Name,
}
var out struct{}
return s.endpoints.Catalog.Deregister(&req, &out)
}
// joinConsulServer is used to try to join another consul server
func (s *Server) joinConsulServer(m serf.Member, parts *serverParts) error {
// Do not join ourself
if m.Name == s.config.NodeName {
return nil
}
// Check for possibility of multiple bootstrap nodes
if parts.Bootstrap {
members := s.serfLAN.Members()
for _, member := range members {
valid, p := isConsulServer(member)
if valid && member.Name != m.Name && p.Bootstrap {
s.logger.Printf("[ERR] consul: '%v' and '%v' are both in bootstrap mode. Only one node should be in bootstrap mode, not adding Raft peer.", m.Name, member.Name)
return nil
}
}
}
// Attempt to add as a peer
var addr net.Addr = &net.TCPAddr{IP: m.Addr, Port: parts.Port}
future := s.raft.AddPeer(addr.String())
if err := future.Error(); err != nil && err != raft.ErrKnownPeer {
s.logger.Printf("[ERR] consul: failed to add raft peer: %v", err)
return err
}
return nil
}
// removeConsulServer is used to try to remove a consul server that has left
func (s *Server) removeConsulServer(m serf.Member, port int) error {
// Attempt to remove as peer
peer := &net.TCPAddr{IP: m.Addr, Port: port}
future := s.raft.RemovePeer(peer.String())
if err := future.Error(); err != nil && err != raft.ErrUnknownPeer {
s.logger.Printf("[ERR] consul: failed to remove raft peer '%v': %v",
peer, err)
return err
} else if err == nil {
s.logger.Printf("[INFO] consul: removed server '%s' as peer", m.Name)
}
return nil
}
// reapTombstones is invoked by the current leader to manage garbage
// collection of tombstones. When a key is deleted, we trigger a tombstone
// GC clock. Once the expiration is reached, this routine is invoked
// to clear all tombstones before this index. This must be replicated
// through Raft to ensure consistency. We do this outside the leader loop
// to avoid blocking.
func (s *Server) reapTombstones(index uint64) {
defer metrics.MeasureSince([]string{"consul", "leader", "reapTombstones"}, time.Now())
req := structs.TombstoneRequest{
Datacenter: s.config.Datacenter,
Op: structs.TombstoneReap,
ReapIndex: index,
WriteRequest: structs.WriteRequest{Token: s.config.ACLToken},
}
_, err := s.raftApply(structs.TombstoneRequestType, &req)
if err != nil {
s.logger.Printf("[ERR] consul: failed to reap tombstones up to %d: %v",
index, err)
}
}