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| 1 | +// Copyright 2018 The Cockroach Authors. |
| 2 | +// |
| 3 | +// Licensed under the Apache License, Version 2.0 (the "License"); |
| 4 | +// you may not use this file except in compliance with the License. |
| 5 | +// You may obtain a copy of the License at |
| 6 | +// |
| 7 | +// http://www.apache.org/licenses/LICENSE-2.0 |
| 8 | +// |
| 9 | +// Unless required by applicable law or agreed to in writing, software |
| 10 | +// distributed under the License is distributed on an "AS IS" BASIS, |
| 11 | +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or |
| 12 | +// implied. See the License for the specific language governing |
| 13 | +// permissions and limitations under the License. |
| 14 | + |
| 15 | +package storage |
| 16 | + |
| 17 | +import ( |
| 18 | + "context" |
| 19 | + "fmt" |
| 20 | + "time" |
| 21 | + |
| 22 | + "github.com/cockroachdb/cockroach/pkg/roachpb" |
| 23 | + "github.com/cockroachdb/cockroach/pkg/util/timeutil" |
| 24 | + "go.etcd.io/etcd/raft" |
| 25 | +) |
| 26 | + |
| 27 | +type splitDelayHelperI interface { |
| 28 | + RaftStatus(context.Context) (roachpb.RangeID, *raft.Status) |
| 29 | + ProposeEmptyCommand(ctx context.Context) |
| 30 | + NumAttempts() int |
| 31 | + Sleep(context.Context) time.Duration |
| 32 | +} |
| 33 | + |
| 34 | +type splitDelayHelper Replica |
| 35 | + |
| 36 | +func (sdh *splitDelayHelper) RaftStatus(ctx context.Context) (roachpb.RangeID, *raft.Status) { |
| 37 | + r := (*Replica)(sdh) |
| 38 | + r.mu.RLock() |
| 39 | + raftStatus := r.raftStatusRLocked() |
| 40 | + if raftStatus != nil { |
| 41 | + updateRaftProgressFromActivity( |
| 42 | + ctx, raftStatus.Progress, r.descRLocked().Replicas, r.mu.lastUpdateTimes, timeutil.Now(), |
| 43 | + ) |
| 44 | + } |
| 45 | + r.mu.RUnlock() |
| 46 | + return r.RangeID, raftStatus |
| 47 | +} |
| 48 | + |
| 49 | +func (sdh *splitDelayHelper) ProposeEmptyCommand(ctx context.Context) { |
| 50 | + r := (*Replica)(sdh) |
| 51 | + r.raftMu.Lock() |
| 52 | + _ = r.withRaftGroup(true /* campaignOnWake */, func(rawNode *raft.RawNode) (bool, error) { |
| 53 | + // NB: intentionally ignore the error (which can be ErrProposalDropped |
| 54 | + // when there's an SST inflight). |
| 55 | + _ = rawNode.Propose(encodeRaftCommandV1(makeIDKey(), nil)) |
| 56 | + // NB: we need to unquiesce as the group might be quiesced. |
| 57 | + return true /* unquiesceAndWakeLeader */, nil |
| 58 | + }) |
| 59 | + r.raftMu.Unlock() |
| 60 | +} |
| 61 | + |
| 62 | +func (sdh *splitDelayHelper) NumAttempts() int { |
| 63 | + return (*Replica)(sdh).store.cfg.RaftDelaySplitToSuppressSnapshotTicks |
| 64 | +} |
| 65 | + |
| 66 | +func (sdh *splitDelayHelper) Sleep(ctx context.Context) time.Duration { |
| 67 | + tBegin := timeutil.Now() |
| 68 | + |
| 69 | + r := (*Replica)(sdh) |
| 70 | + select { |
| 71 | + case <-time.After(r.store.cfg.RaftTickInterval): |
| 72 | + case <-ctx.Done(): |
| 73 | + } |
| 74 | + |
| 75 | + return timeutil.Since(tBegin) |
| 76 | +} |
| 77 | + |
| 78 | +func maybeDelaySplitToAvoidSnapshot(ctx context.Context, sdh splitDelayHelperI) string { |
| 79 | + // We have an "optimization" to avoid Raft snapshots by dropping some |
| 80 | + // outgoing MsgAppResp (see the _ assignment below) which takes effect for |
| 81 | + // RaftPostSplitSuppressSnapshotTicks ticks after an uninitialized replica |
| 82 | + // is created. This check can err, in which case the snapshot will be |
| 83 | + // delayed for that many ticks, and so we want to delay by at least as much |
| 84 | + // plus a bit of padding to give a snapshot a chance to catch the follower |
| 85 | + // up. If we run out of time, we'll resume the split no matter what. |
| 86 | + _ = (*Replica)(nil).maybeDropMsgAppResp // guru assignment |
| 87 | + maxDelaySplitToAvoidSnapshotTicks := sdh.NumAttempts() |
| 88 | + |
| 89 | + var slept time.Duration |
| 90 | + var extra string |
| 91 | + var succeeded bool |
| 92 | + for ticks := 0; ticks < maxDelaySplitToAvoidSnapshotTicks; ticks++ { |
| 93 | + succeeded = false |
| 94 | + extra = "" |
| 95 | + rangeID, raftStatus := sdh.RaftStatus(ctx) |
| 96 | + |
| 97 | + if raftStatus == nil { |
| 98 | + // Don't delay on followers (we don't know when to stop). This case |
| 99 | + // is hit rarely enough to not matter. |
| 100 | + extra += "; not Raft leader" |
| 101 | + succeeded = true |
| 102 | + break |
| 103 | + } |
| 104 | + |
| 105 | + done := true |
| 106 | + for replicaID, pr := range raftStatus.Progress { |
| 107 | + if replicaID == raftStatus.Lead { |
| 108 | + // TODO(tschottdorf): remove this once we have picked up |
| 109 | + // https://github.com/etcd-io/etcd/pull/10279 |
| 110 | + continue |
| 111 | + } |
| 112 | + |
| 113 | + if pr.State != raft.ProgressStateReplicate { |
| 114 | + if !pr.RecentActive { |
| 115 | + if ticks == 0 { |
| 116 | + // Having set done = false, we make sure we're not exiting early. |
| 117 | + // This is important because we sometimes need that Raft proposal |
| 118 | + // below to make the followers active as there's no chatter on an |
| 119 | + // idle range. (Note that there's a theoretical race in which the |
| 120 | + // follower becomes inactive again during the sleep, but the |
| 121 | + // inactivity interval is much larger than a tick). |
| 122 | + // |
| 123 | + // Don't do this more than once though: if a follower is down, |
| 124 | + // we don't want to delay splits for it. |
| 125 | + done = false |
| 126 | + } |
| 127 | + extra += fmt.Sprintf("; r%d/%d inactive", rangeID, replicaID) |
| 128 | + continue |
| 129 | + } |
| 130 | + done = false |
| 131 | + extra += fmt.Sprintf("; replica r%d/%d not caught up: %+v", rangeID, replicaID, &pr) |
| 132 | + } |
| 133 | + } |
| 134 | + if done { |
| 135 | + succeeded = true |
| 136 | + break |
| 137 | + } |
| 138 | + // Propose an empty command which works around a Raft bug that can |
| 139 | + // leave a follower in ProgressStateProbe even though it has caught |
| 140 | + // up. |
| 141 | + sdh.ProposeEmptyCommand(ctx) |
| 142 | + slept += sdh.Sleep(ctx) |
| 143 | + |
| 144 | + if ctx.Err() != nil { |
| 145 | + return "" |
| 146 | + } |
| 147 | + } |
| 148 | + |
| 149 | + if slept != 0 { |
| 150 | + extra += fmt.Sprintf("; delayed split for %.1fs to avoid Raft snapshot", slept.Seconds()) |
| 151 | + if !succeeded { |
| 152 | + extra += " (without success)" |
| 153 | + } |
| 154 | + } |
| 155 | + |
| 156 | + return extra |
| 157 | +} |
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