/
merge_manager.go
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/
merge_manager.go
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// 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 cellar
import (
"fmt"
"sync"
"sync/atomic"
)
type mergeManager struct {
cellar *Cellar
changes chan segmentList
closeChan chan struct{}
mutex sync.Mutex
running bool
wg sync.WaitGroup
policy MergePolicy
auto bool
mergeWork chan *Merge
maxConcurrent int
}
func newMergeManager(cellar *Cellar, policy MergePolicy, auto bool, maxConcurrent int) *mergeManager {
rv := &mergeManager{
changes: make(chan segmentList),
closeChan: make(chan struct{}),
running: false,
policy: policy,
auto: auto,
mergeWork: make(chan *Merge, 1024),
cellar: cellar,
maxConcurrent: maxConcurrent,
}
return rv
}
func (m *mergeManager) Start() error {
m.mutex.Lock()
defer m.mutex.Unlock()
if m.running {
return fmt.Errorf("already running")
}
m.running = true
// start workers
for i := 0; i < m.maxConcurrent; i++ {
m.wg.Add(1)
go mergeWorker(&m.wg, m.mergeWork, m.closeChan)
}
m.wg.Add(1)
go m.Run()
return nil
}
func (m *mergeManager) Run() {
OUTER:
for {
select {
case <-m.closeChan:
break OUTER
case newRoot, ok := <-m.changes:
if !ok {
break OUTER
} else {
// roots changed, see if any merges should be done
merges := m.policy.Merges(m.cellar, newRoot)
for _, merge := range merges {
// assign this merge a new segment seq
merge.newSegmentSeq = atomic.AddUint64(&m.cellar.seq, 1)
// set mergeInProgress so we don't keep merging the same segments
for _, s := range merge.sources {
s.mergeInProgress = merge.newSegmentSeq
// also incr ref count for each source
s.incrRef("merge work")
}
m.mergeWork <- merge
}
// release refs
for _, segment := range newRoot {
segment.decrRef("merge notification")
}
}
}
}
m.wg.Done()
}
func (m *mergeManager) Stop() error {
Logger.Printf("staring to close merge manager")
close(m.closeChan)
m.wg.Wait()
Logger.Printf("done closing merge manager")
// drain anything left on merge work and decr refs
close(m.mergeWork)
OUTER:
for {
select {
case work, ok := <-m.mergeWork:
if !ok {
break OUTER
}
for _, s := range work.sources {
s.decrRef("draining merge work")
}
}
}
return nil
}
func (m *mergeManager) RootChange(root segmentList) {
if m.auto {
m.changes <- root
} else {
// release refs
for _, segment := range root {
segment.decrRef("no automatic mergin")
}
}
}
func (m *mergeManager) ForceMerge(root segmentList) {
m.changes <- root
}
func mergeWorker(wg *sync.WaitGroup, workChan chan *Merge, closeChan chan struct{}) {
OUTER:
for {
select {
case <-closeChan:
break OUTER
case work, ok := <-workChan:
if !ok {
break OUTER
}
err := doMerge(work)
if err != nil {
Logger.Printf("MERGE ERROR: %v", err)
}
}
}
wg.Done()
Logger.Printf("merge worker done")
}