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domain: close slow query channel after closing session pool #7847

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merged 5 commits into from
Oct 11, 2018
Merged

domain: close slow query channel after closing session pool #7847

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domain: close slow query channel after closing session pool
tiancaiamao Oct 9, 2018
477672a
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tiancaiamao Oct 10, 2018
5ebd928
address comment
tiancaiamao Oct 11, 2018
fed5327
Merge branch 'master' into close-slow-query
tiancaiamao Oct 11, 2018
ee75a5e
Merge branch 'master' into close-slow-query
zz-jason Oct 11, 2018
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8 changes: 7 additions & 1 deletion domain/domain.go
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Original file line number Diff line number Diff line change
Expand Up @@ -337,6 +337,12 @@ func (do *Domain) Reload() error {

// LogSlowQuery keeps topN recent slow queries in domain.
func (do *Domain) LogSlowQuery(query *SlowQueryInfo) {
do.slowQuery.mu.RLock()
defer do.slowQuery.mu.RUnlock()
if do.slowQuery.mu.closed {
return
}

select {
case do.slowQuery.ch <- query:
default:
Expand Down Expand Up @@ -459,8 +465,8 @@ func (do *Domain) Close() {
if do.etcdClient != nil {
terror.Log(errors.Trace(do.etcdClient.Close()))
}
do.slowQuery.Close()
do.sysSessionPool.Close()
do.slowQuery.Close()
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Is it enough to put “do.slowQuery.Close()” after line462?

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do.slowQuery.Close() will make goroutine exit and WaitGroup count -1.
If this line is moved to line 462,do.wg.Wait() would wait forever.

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Ignore it.

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But I think it's useless. After this function is executed, "updateStatsWorker" may still be called by another goroutine. This problem still exists.
Maybe we can replace "ctx"(the updateStatsWorker's argument) with the session created in the sysSessionPool.

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Do you mean after session pool is closed, updateStatsWorker will be still executing ? @zimulala

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Ye. Because the session used in statistic bootstrap is not get from session pool. @tiancaiamao

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Current session pool implementation will block waiting resource to be put back, so after the pool is closed, there won't be system session running. @crazycs520 @zimulala

do.wg.Wait()
log.Info("[domain] close")
}
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9 changes: 9 additions & 0 deletions domain/topn_slow_query.go
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Expand Up @@ -115,6 +115,11 @@ type topNSlowQueries struct {
period time.Duration
ch chan *SlowQueryInfo
msgCh chan *showSlowMessage

mu struct {
sync.RWMutex
closed bool
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how about use atomic instead of mutex.

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@tiancaiamao tiancaiamao Oct 11, 2018 •
edited
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atomic can't protect multiple operations. @crazycs520

modify atomic flag
close(ch)

check atomic flag
ch <-

Take this order for example:

  1. check atomic flag = success
  2. modify atomic flag = closed
  3. close(ch)
  4. <-ch panic!

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great~

}
}

func newTopNSlowQueries(topN int, period time.Duration, queueSize int) *topNSlowQueries {
Expand Down Expand Up @@ -196,6 +201,10 @@ func (q *topNSlowQueries) QueryTop(count int, kind ast.ShowSlowKind) []*SlowQuer
}

func (q *topNSlowQueries) Close() {
q.mu.Lock()
q.mu.closed = true
q.mu.Unlock()

close(q.ch)
}

Expand Down