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contractcourt: make synchronous chain watcher notifications optional

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In this commit, we modify the way that notifications are dispatched
within the chainWatcher. Before we would *always* wait for an ack back
before we started to clean up he database state. This would at times
lead to deadlocks. To remedy this, we now allow callers to decide if
they want notifications to be sync or not. The only current caller that
requires this is the breach arbiter.
This commit is contained in:
Olaoluwa Osuntokun
2018-01-20 20:25:54 -08:00
parent f85f1f97ca
commit 5df6704a9c
5 changed files with 57 additions and 31 deletions
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49
contractcourt/chain_watcher.go
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@@ -45,7 +45,10 @@ type ChainEventSubscription struct {
// synchronize dispatch and processing of the notification with the act
// of updating the state of the channel on disk. This ensures that the
// event can be reliably handed off.
ProcessACK chan struct{}
//
// NOTE: This channel will only be used if the syncDispatch arg passed
// into the constructor is true.
ProcessACK chan error
// Cancel cancels the subscription to the event stream for a particular
// channel. This method should be called once the caller no longer needs to
@@ -89,7 +92,7 @@ type chainWatcher struct {
signer lnwallet.Signer
// All the fields below are protected by this mutex.
sync.RWMutex
sync.Mutex
// clientID is an ephemeral counter used to keep track of each
// individual client subscription.
@@ -207,13 +210,17 @@ func (c *chainWatcher) Stop() error {
// SubscribeChannelEvents returns a n active subscription to the set of channel
// events for the channel watched by this chain watcher. Once clients no longer
// require the subscription, they should call the Cancel() method to allow the
// watcher to regain those committed resources.
func (c *chainWatcher) SubscribeChannelEvents() *ChainEventSubscription {
c.Lock()
defer c.Unlock()
// watcher to regain those committed resources. The syncDispatch bool indicates
// if the caller would like a synchronous dispatch of the notification. This
// means that the main chain watcher goroutine won't proceed with
// post-processing after the notification until the ProcessACK channel is sent
// upon.
func (c *chainWatcher) SubscribeChannelEvents(syncDispatch bool) *ChainEventSubscription {
c.Lock()
clientID := c.clientID
c.clientID++
c.Unlock()
log.Debugf("New ChainEventSubscription(id=%v) for ChannelPoint(%v)",
clientID, c.chanState.FundingOutpoint)
@@ -231,7 +238,13 @@ func (c *chainWatcher) SubscribeChannelEvents() *ChainEventSubscription {
},
}
if syncDispatch {
sub.ProcessACK = make(chan error, 1)
}
c.Lock()
c.clientSubscriptions[clientID] = sub
c.Unlock()
return sub
}
@@ -547,7 +560,6 @@ func (c *chainWatcher) dispatchContractBreach(spendEvent *chainntnfs.SpendDetail
}
var (
broadcastStateNum = remoteCommit.CommitHeight
commitTxBroadcast = spendEvent.SpendingTx
spendHeight = uint32(spendEvent.SpendingHeight)
)
@@ -578,17 +590,20 @@ func (c *chainWatcher) dispatchContractBreach(spendEvent *chainntnfs.SpendDetail
}
// Wait for the breach arbiter to ACK the handoff before
// marking the channel as pending force closed in channeldb.
select {
case <-sub.ProcessACK:
// Bail if the handoff failed.
if err != nil {
return fmt.Errorf("unable to handoff "+
"retribution info: %v", err)
}
// marking the channel as pending force closed in channeldb,
// but only if the client requested a sync dispatch.
if sub.ProcessACK != nil {
select {
case err := <-sub.ProcessACK:
// Bail if the handoff failed.
if err != nil {
return fmt.Errorf("unable to handoff "+
"retribution info: %v", err)
}
case <-c.quit:
return fmt.Errorf("quitting")
case <-c.quit:
return fmt.Errorf("quitting")
}
}
}
c.Unlock()