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les: fix retriever logic (#16776)

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This PR fixes a retriever logic bug. When a peer had a soft timeout
and then a response arrived, it always assumed it was the same peer
even though it could have been a later requested one that did not time
out at all yet. In this case the logic went to an illegal state and
deadlocked, causing a goroutine leak.

Fixes #16243 and replaces #16359.
Thanks to @riceke for finding the bug in the logic.
This commit is contained in:
Felföldi Zsolt 2018-06-12 15:58:47 +02:00 committed by Felix Lange
parent 049f5b3572
commit 25982375a8
1 changed files with 17 additions and 13 deletions
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30
les/retrieve.go
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@ -69,9 +69,9 @@ type sentReq struct {
lock sync.RWMutex // protect access to sentTo map lock sync.RWMutex // protect access to sentTo map
sentTo map[distPeer]sentReqToPeer sentTo map[distPeer]sentReqToPeer
reqQueued bool // a request has been queued but not sent lastReqQueued bool // last request has been queued but not sent
reqSent bool // a request has been sent but not timed out lastReqSentTo distPeer // if not nil then last request has been sent to given peer but not timed out
reqSrtoCount int // number of requests that reached soft (but not hard) timeout reqSrtoCount int // number of requests that reached soft (but not hard) timeout
} }
// sentReqToPeer notifies the request-from-peer goroutine (tryRequest) about a response // sentReqToPeer notifies the request-from-peer goroutine (tryRequest) about a response
@ -180,7 +180,7 @@ type reqStateFn func() reqStateFn
// retrieveLoop is the retrieval state machine event loop // retrieveLoop is the retrieval state machine event loop
func (r *sentReq) retrieveLoop() { func (r *sentReq) retrieveLoop() {
go r.tryRequest() go r.tryRequest()
r.reqQueued = true r.lastReqQueued = true
state := r.stateRequesting state := r.stateRequesting
for state != nil { for state != nil {
@ -214,7 +214,7 @@ func (r *sentReq) stateRequesting() reqStateFn {
case rpSoftTimeout: case rpSoftTimeout:
// last request timed out, try asking a new peer // last request timed out, try asking a new peer
go r.tryRequest() go r.tryRequest()
r.reqQueued = true r.lastReqQueued = true
return r.stateRequesting return r.stateRequesting
case rpDeliveredValid: case rpDeliveredValid:
r.stop(nil) r.stop(nil)
@ -233,7 +233,7 @@ func (r *sentReq) stateNoMorePeers() reqStateFn {
select { select {
case <-time.After(retryQueue): case <-time.After(retryQueue):
go r.tryRequest() go r.tryRequest()
r.reqQueued = true r.lastReqQueued = true
return r.stateRequesting return r.stateRequesting
case ev := <-r.eventsCh: case ev := <-r.eventsCh:
r.update(ev) r.update(ev)
@ -260,22 +260,26 @@ func (r *sentReq) stateStopped() reqStateFn {
func (r *sentReq) update(ev reqPeerEvent) { func (r *sentReq) update(ev reqPeerEvent) {
switch ev.event { switch ev.event {
case rpSent: case rpSent:
r.reqQueued = false r.lastReqQueued = false
if ev.peer != nil { r.lastReqSentTo = ev.peer
r.reqSent = true
}
case rpSoftTimeout: case rpSoftTimeout:
r.reqSent = false r.lastReqSentTo = nil
r.reqSrtoCount++ r.reqSrtoCount++
case rpHardTimeout, rpDeliveredValid, rpDeliveredInvalid: case rpHardTimeout:
r.reqSrtoCount-- r.reqSrtoCount--
case rpDeliveredValid, rpDeliveredInvalid:
if ev.peer == r.lastReqSentTo {
r.lastReqSentTo = nil
} else {
r.reqSrtoCount--
}
} }
} }
// waiting returns true if the retrieval mechanism is waiting for an answer from // waiting returns true if the retrieval mechanism is waiting for an answer from
// any peer // any peer
func (r *sentReq) waiting() bool { func (r *sentReq) waiting() bool {
return r.reqQueued || r.reqSent || r.reqSrtoCount > 0 return r.lastReqQueued || r.lastReqSentTo != nil || r.reqSrtoCount > 0
} }
// tryRequest tries to send the request to a new peer and waits for it to either // tryRequest tries to send the request to a new peer and waits for it to either