forked from cockroachdb/cockroach
/
replicate_queue.go
355 lines (327 loc) · 11.7 KB
/
replicate_queue.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
// Copyright 2015 The Cockroach Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
// implied. See the License for the specific language governing
// permissions and limitations under the License.
//
// Author: Ben Darnell
package storage
import (
"time"
"github.com/pkg/errors"
"golang.org/x/net/context"
"github.com/cockroachdb/cockroach/pkg/config"
"github.com/cockroachdb/cockroach/pkg/gossip"
"github.com/cockroachdb/cockroach/pkg/roachpb"
"github.com/cockroachdb/cockroach/pkg/util/hlc"
"github.com/cockroachdb/cockroach/pkg/util/log"
"github.com/cockroachdb/cockroach/pkg/util/timeutil"
)
const (
// replicateQueueMaxSize is the max size of the replicate queue.
replicateQueueMaxSize = 100
// replicateQueueTimerDuration is the duration between replication of queued
// replicas.
replicateQueueTimerDuration = 0 // zero duration to process replication greedily
)
var (
// minLeaseTransferInterval controls how frequently leases can be transferred
// for rebalancing. It does not prevent transferring leases in order to allow
// a replica to be removed from a range. The value should be some reasonable
// fraction of the store descriptor gossip interval which currently
minLeaseTransferInterval = gossip.GossipStoresInterval / 5
)
// replicateQueue manages a queue of replicas which may need to add an
// additional replica to their range.
type replicateQueue struct {
*baseQueue
allocator Allocator
clock *hlc.Clock
updateChan chan struct{}
lastLeaseTransfer time.Time
}
// newReplicateQueue returns a new instance of replicateQueue.
func newReplicateQueue(
store *Store, g *gossip.Gossip, allocator Allocator, clock *hlc.Clock, options AllocatorOptions,
) *replicateQueue {
rq := &replicateQueue{
allocator: allocator,
clock: clock,
updateChan: make(chan struct{}, 1),
}
rq.baseQueue = newBaseQueue(
"replicate", rq, store, g,
queueConfig{
maxSize: replicateQueueMaxSize,
needsLease: true,
acceptsUnsplitRanges: store.TestingKnobs().ReplicateQueueAcceptsUnsplit,
successes: store.metrics.ReplicateQueueSuccesses,
failures: store.metrics.ReplicateQueueFailures,
pending: store.metrics.ReplicateQueuePending,
processingNanos: store.metrics.ReplicateQueueProcessingNanos,
purgatory: store.metrics.ReplicateQueuePurgatory,
},
)
if g != nil { // gossip is nil for some unittests
// Register a gossip callback to signal queue that replicas in
// purgatory might be retried due to new store gossip.
g.RegisterCallback(gossip.MakePrefixPattern(gossip.KeyStorePrefix), func(_ string, _ roachpb.Value) {
select {
case rq.updateChan <- struct{}{}:
default:
}
})
}
return rq
}
func (rq *replicateQueue) shouldQueue(
ctx context.Context, now hlc.Timestamp, repl *Replica, sysCfg config.SystemConfig,
) (shouldQ bool, priority float64) {
if !repl.store.splitQueue.Disabled() && repl.needsSplitBySize() {
// If the range exceeds the split threshold, let that finish first.
// Ranges must fit in memory on both sender and receiver nodes while
// being replicated. This supplements the check provided by
// acceptsUnsplitRanges, which looks at zone config boundaries rather
// than data size.
//
// This check is ignored if the split queue is disabled, since in that
// case, the split will never come.
return
}
// Find the zone config for this range.
desc := repl.Desc()
zone, err := sysCfg.GetZoneConfigForKey(desc.StartKey)
if err != nil {
log.Error(ctx, err)
return
}
action, priority := rq.allocator.ComputeAction(zone, desc)
if action != AllocatorNoop {
if log.V(2) {
log.Infof(ctx, "%s repair needed (%s), enqueuing", repl, action)
}
return true, priority
}
// If we hold the lease, check to see if we should transfer it.
var leaseStoreID roachpb.StoreID
if lease, _ := repl.getLease(); lease != nil && lease.Covers(now) {
leaseStoreID = lease.Replica.StoreID
if rq.canTransferLease() &&
rq.allocator.ShouldTransferLease(zone.Constraints, leaseStoreID, desc.RangeID) {
if log.V(2) {
log.Infof(ctx, "%s lease transfer needed, enqueuing", repl)
}
return true, 0
}
}
// Check for a rebalancing opportunity. Note that leaseStoreID will be 0 if
// the range doesn't currently have a lease which will allow the current
// replica to be considered a rebalancing source.
target, err := rq.allocator.RebalanceTarget(
zone.Constraints,
desc.Replicas,
leaseStoreID,
desc.RangeID,
)
if err != nil {
log.ErrEventf(ctx, "rebalance target failed: %s", err)
return false, 0
}
if log.V(2) {
if target != nil {
log.Infof(ctx, "%s rebalance target found, enqueuing", repl)
} else {
log.Infof(ctx, "%s no rebalance target found, not enqueuing", repl)
}
}
return target != nil, 0
}
func (rq *replicateQueue) process(
ctx context.Context, now hlc.Timestamp, repl *Replica, sysCfg config.SystemConfig,
) error {
desc := repl.Desc()
// Find the zone config for this range.
zone, err := sysCfg.GetZoneConfigForKey(desc.StartKey)
if err != nil {
return err
}
action, _ := rq.allocator.ComputeAction(zone, desc)
// Avoid taking action if the range has too many dead replicas to make
// quorum.
deadReplicas := rq.allocator.storePool.deadReplicas(desc.RangeID, desc.Replicas)
quorum := computeQuorum(len(desc.Replicas))
liveReplicaCount := len(desc.Replicas) - len(deadReplicas)
if liveReplicaCount < quorum {
return errors.Errorf("range requires a replication change, but lacks a quorum of live nodes.")
}
switch action {
case AllocatorAdd:
log.Event(ctx, "adding a new replica")
newStore, err := rq.allocator.AllocateTarget(
zone.Constraints,
desc.Replicas,
desc.RangeID,
true,
)
if err != nil {
return err
}
newReplica := roachpb.ReplicaDescriptor{
NodeID: newStore.Node.NodeID,
StoreID: newStore.StoreID,
}
log.VEventf(ctx, 1, "adding replica to %+v due to under-replication", newReplica)
if err := rq.addReplica(ctx, repl, newReplica, desc); err != nil {
return err
}
case AllocatorRemove:
log.Event(ctx, "removing a replica")
// If the lease holder (our local store) is an overfull store (in terms of
// leases) allow transferring the lease away.
leaseHolderStoreID := repl.store.StoreID()
if rq.allocator.ShouldTransferLease(zone.Constraints, leaseHolderStoreID, desc.RangeID) {
leaseHolderStoreID = 0
}
removeReplica, err := rq.allocator.RemoveTarget(
zone.Constraints,
desc.Replicas,
leaseHolderStoreID,
)
if err != nil {
return err
}
if removeReplica.StoreID == repl.store.StoreID() {
// The local replica was selected as the removal target, but that replica
// is the leaseholder, so transfer the lease instead. We don't check that
// the current store has too many leases in this case under the
// assumption that replica balance is a greater concern. Also note that
// AllocatorRemove action takes preference over AllocatorNoop
// (rebalancing) which is where lease transfer would otherwise occur. We
// need to be able to transfer leases in AllocatorRemove in order to get
// out of situations where this store is overfull and yet holds all the
// leases.
target := rq.allocator.TransferLeaseTarget(
zone.Constraints, desc.Replicas, repl.store.StoreID(), desc.RangeID,
false /* checkTransferLeaseSource */)
if target != (roachpb.ReplicaDescriptor{}) {
log.VEventf(ctx, 1, "transferring lease to s%d", target.StoreID)
if err := repl.AdminTransferLease(target.StoreID); err != nil {
return errors.Wrapf(err, "%s: unable to transfer lease to s%d", repl, target.StoreID)
}
rq.lastLeaseTransfer = timeutil.Now()
// Do not requeue as we transferred our lease away.
return nil
}
} else {
log.VEventf(ctx, 1, "removing replica %+v due to over-replication", removeReplica)
if err := rq.removeReplica(ctx, repl, removeReplica, desc); err != nil {
return err
}
}
case AllocatorRemoveDead:
log.Event(ctx, "removing a dead replica")
if len(deadReplicas) == 0 {
if log.V(1) {
log.Warningf(ctx, "Range of replica %s was identified as having dead replicas, but no dead replicas were found.", repl)
}
break
}
deadReplica := deadReplicas[0]
log.VEventf(ctx, 1, "removing dead replica %+v from store", deadReplica)
if err := repl.ChangeReplicas(ctx, roachpb.REMOVE_REPLICA, deadReplica, desc); err != nil {
return err
}
case AllocatorNoop:
// The Noop case will result if this replica was queued in order to
// rebalance. Attempt to find a rebalancing target.
log.Event(ctx, "considering a rebalance")
if rq.canTransferLease() {
// We require the lease in order to process replicas, so
// repl.store.StoreID() corresponds to the lease-holder's store ID.
target := rq.allocator.TransferLeaseTarget(
zone.Constraints, desc.Replicas, repl.store.StoreID(), desc.RangeID,
true /* checkTransferLeaseSource */)
if target.StoreID != 0 {
log.VEventf(ctx, 1, "transferring lease to s%d", target.StoreID)
if err := repl.AdminTransferLease(target.StoreID); err != nil {
return errors.Wrapf(err, "%s: unable to transfer lease to s%d", repl, target.StoreID)
}
rq.lastLeaseTransfer = timeutil.Now()
// Do not requeue as we transferred our lease away.
return nil
}
}
rebalanceStore, err := rq.allocator.RebalanceTarget(
zone.Constraints,
desc.Replicas,
repl.store.StoreID(),
desc.RangeID,
)
if err != nil {
log.ErrEventf(ctx, "rebalance target failed %s", err)
return nil
}
if rebalanceStore == nil {
log.VEventf(ctx, 1, "no suitable rebalance target")
// No action was necessary and no rebalance target was found. Return
// without re-queuing this replica.
return nil
}
rebalanceReplica := roachpb.ReplicaDescriptor{
NodeID: rebalanceStore.Node.NodeID,
StoreID: rebalanceStore.StoreID,
}
log.VEventf(ctx, 1, "rebalancing to %+v", rebalanceReplica)
if err := rq.addReplica(ctx, repl, rebalanceReplica, desc); err != nil {
return err
}
}
// Enqueue this replica again to see if there are more changes to be made.
rq.MaybeAdd(repl, rq.clock.Now())
return nil
}
func (rq *replicateQueue) addReplica(
ctx context.Context,
repl *Replica,
repDesc roachpb.ReplicaDescriptor,
desc *roachpb.RangeDescriptor,
) error {
err := repl.ChangeReplicas(ctx, roachpb.ADD_REPLICA, repDesc, desc)
if IsPreemptiveSnapshotError(err) {
// If the ChangeReplicas failed because the preemptive snapshot failed, we
// log the error but then return success indicating we should retry the
// operation. The most likely causes of the preemptive snapshot failing are
// a declined reservation or the remote node being unavailable. In either
// case we don't want to wait another scanner cycle before reconsidering
// the range.
log.Info(ctx, err)
return nil
}
return err
}
func (rq *replicateQueue) removeReplica(
ctx context.Context,
repl *Replica,
repDesc roachpb.ReplicaDescriptor,
desc *roachpb.RangeDescriptor,
) error {
return repl.ChangeReplicas(ctx, roachpb.REMOVE_REPLICA, repDesc, desc)
}
func (rq *replicateQueue) canTransferLease() bool {
return timeutil.Since(rq.lastLeaseTransfer) > minLeaseTransferInterval
}
func (*replicateQueue) timer() time.Duration {
return replicateQueueTimerDuration
}
// purgatoryChan returns the replicate queue's store update channel.
func (rq *replicateQueue) purgatoryChan() <-chan struct{} {
return rq.updateChan
}