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Allow cancelling blocking queries in response to shutting down.

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This commit is contained in:
Matt Keeler 2020-06-24 12:36:54 -04:00
parent 341aedbce9
commit 90e741c6d2
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GPG key ID: 04DBAE1857E0081B
2 changed files with 19 additions and 9 deletions
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13
agent/agent.go
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@ -4424,7 +4424,8 @@ func (a *Agent) LocalBlockingQuery(alwaysBlock bool, hash string, wait time.Dura
// If we are not blocking we can skip tracking and allocating - nil WatchSet
// is still valid to call Add on and will just be a no op.
var ws memdb.WatchSet
var timeout *time.Timer
var ctx context.Context = &lib.StopChannelContext{StopCh: a.shutdownCh}
shouldBlock := false
if alwaysBlock || hash != "" {
if wait == 0 {
@ -4435,7 +4436,11 @@ func (a *Agent) LocalBlockingQuery(alwaysBlock bool, hash string, wait time.Dura
}
// Apply a small amount of jitter to the request.
wait += lib.RandomStagger(wait / 16)
timeout = time.NewTimer(wait)
var cancel func()
ctx, cancel = context.WithDeadline(ctx, time.Now().Add(wait))
defer cancel()
shouldBlock = true
}
for {
@ -4453,7 +4458,7 @@ func (a *Agent) LocalBlockingQuery(alwaysBlock bool, hash string, wait time.Dura
// WatchSet immediately returns false which would incorrectly cause this to
// loop and repeat again, however we rely on the invariant that ws == nil
// IFF timeout == nil in which case the Watch call is never invoked.
if timeout == nil || hash != curHash || ws.Watch(timeout.C) {
if !shouldBlock || hash != curHash || ws.WatchCtx(ctx) != nil {
return curHash, curResp, err
}
// Watch returned false indicating a change was detected, loop and repeat
@ -4465,7 +4470,7 @@ func (a *Agent) LocalBlockingQuery(alwaysBlock bool, hash string, wait time.Dura
if syncPauseCh := a.SyncPausedCh(); syncPauseCh != nil {
select {
case <-syncPauseCh:
case <-timeout.C:
case <-ctx.Done():
}
}
}

15
agent/consul/rpc.go
View file

@ -1,6 +1,7 @@
package consul
import (
"context"
"crypto/tls"
"encoding/binary"
"errors"
@ -752,7 +753,9 @@ type queryFn func(memdb.WatchSet, *state.Store) error
// blockingQuery is used to process a potentially blocking query operation.
func (s *Server) blockingQuery(queryOpts structs.QueryOptionsCompat, queryMeta structs.QueryMetaCompat, fn queryFn) error {
var timeout *time.Timer
var cancel func()
var ctx context.Context = &lib.StopChannelContext{StopCh: s.shutdownCh}
var queriesBlocking uint64
var queryTimeout time.Duration
@ -776,9 +779,9 @@ func (s *Server) blockingQuery(queryOpts structs.QueryOptionsCompat, queryMeta s
// Apply a small amount of jitter to the request.
queryTimeout += lib.RandomStagger(queryTimeout / jitterFraction)
// Setup a query timeout.
timeout = time.NewTimer(queryTimeout)
defer timeout.Stop()
// wrap the base context with a deadline
ctx, cancel = context.WithDeadline(ctx, time.Now().Add(queryTimeout))
defer cancel()
// instrument blockingQueries
// atomic inc our server's count of in-flight blockingQueries and store the new value
@ -833,7 +836,9 @@ RUN_QUERY:
}
// block up to the timeout if we don't see anything fresh.
if err == nil && minQueryIndex > 0 && queryMeta.GetIndex() <= minQueryIndex {
if expired := ws.Watch(timeout.C); !expired {
if err := ws.WatchCtx(ctx); err == nil {
// a non-nil error only occurs when the context is cancelled
// If a restore may have woken us up then bail out from
// the query immediately. This is slightly race-ey since
// this might have been interrupted for other reasons,