/usr/share/gocode/src/github.com/couchbase/moss/persister.go is in golang-github-couchbase-moss-dev 0.0~git20170914.0.07c86e8-4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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 | // Copyright (c) 2016 Couchbase, Inc.
// 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.
package moss
import (
"sync/atomic"
"time"
)
// runPersister() implements the persister task.
func (m *collection) runPersister() {
defer func() {
close(m.donePersisterCh)
atomic.AddUint64(&m.stats.TotPersisterEnd, 1)
}()
if m.options.LowerLevelUpdate == nil {
return
}
OUTER:
for {
atomic.AddUint64(&m.stats.TotPersisterLoop, 1)
m.m.Lock()
for m.stackDirtyBase == nil && !m.isClosed() {
// There's a concurrency scenario where imagine that
// persistence takes a long time. Also, imagine that
// there are no more incoming batches (so, stackDirtyTop
// is empty).
//
// That allows the merger to complete a merging cycle (so,
// stackDirtyMid is non-empty with unpersisted data) and
// the merger is now just waiting for either more incoming
// batches or waiting to be awoken.
//
// So, we notify/awake the merger here so that it can feed
// stackDirtyMid down to the persister as stackDirtyBase.
if m.waitDirtyIncomingCh != nil && // Merger is indeed asleep.
(m.stackDirtyMid != nil && len(m.stackDirtyMid.a) > 0) &&
(m.stackDirtyTop == nil || len(m.stackDirtyTop.a) <= 0) {
m.NotifyMerger("from-persister", false)
}
atomic.AddUint64(&m.stats.TotPersisterWaitBeg, 1)
m.stackDirtyBaseCond.Wait()
atomic.AddUint64(&m.stats.TotPersisterWaitEnd, 1)
}
stackDirtyBase := m.stackDirtyBase
m.m.Unlock()
if m.isClosed() {
return
}
startTime := time.Now()
atomic.AddUint64(&m.stats.TotPersisterLowerLevelUpdateBeg, 1)
llssNext, err := m.options.LowerLevelUpdate(stackDirtyBase)
if err != nil {
atomic.AddUint64(&m.stats.TotPersisterLowerLevelUpdateErr, 1)
m.Logf("collection: runPersister, LowerLevelUpdate, err: %v", err)
m.OnError(err)
continue OUTER
}
atomic.AddUint64(&m.stats.TotPersisterLowerLevelUpdateEnd, 1)
var stackDirtyBasePrev *segmentStack
var stackCleanPrev *segmentStack
m.m.Lock()
m.invalidateLatestSnapshotLOCKED()
stackCleanPrev = m.stackClean
if m.options.CachePersisted {
m.stackClean = m.stackDirtyBase
} else {
m.stackClean = nil
stackDirtyBasePrev = m.stackDirtyBase
}
m.stackDirtyBase = nil
waitDirtyOutgoingCh := m.waitDirtyOutgoingCh
m.waitDirtyOutgoingCh = nil
llssPrev := m.lowerLevelSnapshot
m.lowerLevelSnapshot = NewSnapshotWrapper(llssNext, nil)
m.m.Unlock()
if stackDirtyBasePrev != nil {
stackDirtyBasePrev.Close()
}
if stackCleanPrev != nil {
stackCleanPrev.Close()
}
if llssPrev != nil {
llssPrev.Close()
}
if waitDirtyOutgoingCh != nil {
close(waitDirtyOutgoingCh)
}
// ---------------------------------------------
atomic.AddUint64(&m.stats.TotPersisterLoopRepeat, 1)
m.fireEvent(EventKindPersisterProgress, time.Now().Sub(startTime))
}
// TODO: More advanced eviction of stackClean.
// TODO: Timer based eviction of stackClean?
// TODO: Randomized eviction?
// TODO: Merging of stackClean to 1 level?
// TODO: WaitForMerger() also considers stackClean?
// TODO: Track popular Get() keys?
// TODO: Track shadowing during merges for writes.
}
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