From 6c6e66f7b2e776add2bfbfbafa9c991c90bc15f4 Mon Sep 17 00:00:00 2001
From: Silas Davis <silas@erisindustries.com>
Date: Fri, 9 Sep 2016 20:17:06 +0100
Subject: [PATCH] Fix blocking event subscription in transactAndHold
---
manager/eris-mint/transactor.go | 19 +++++++++++++++----
1 file changed, 15 insertions(+), 4 deletions(-)
diff --git a/manager/eris-mint/transactor.go b/manager/eris-mint/transactor.go
index fd920145..23012e4a 100644
--- a/manager/eris-mint/transactor.go
+++ b/manager/eris-mint/transactor.go
@@ -205,13 +205,24 @@ func (this *transactor) TransactAndHold(privKey, address, data []byte, gasLimit,
} else {
addr = address
}
- wc := make(chan *txs.EventDataCall)
+ // We want non-blocking on the first event received (but buffer the value),
+ // after which we want to block (and then discard the value - see below)
+ wc := make(chan *txs.EventDataCall, 1)
subId := fmt.Sprintf("%X", rec.TxHash)
this.eventEmitter.Subscribe(subId, txs.EventStringAccCall(addr),
func(evt txs.EventData) {
- event := evt.(txs.EventDataCall)
- if bytes.Equal(event.TxID, rec.TxHash) {
- wc <- &event
+ eventDataCall := evt.(txs.EventDataCall)
+ if bytes.Equal(eventDataCall.TxID, rec.TxHash) {
+ // Beware the contract of go-events subscribe is that we must not be
+ // blocking in an event callback when we try to unsubscribe!
+ // We work around this by using a non-blocking send.
+ select {
+ // This is a non-blocking send, but since we are using a buffered
+ // channel of size 1 we will always grab our first event even if we
+ // haven't read from the channel at the time we receive the first event.
+ case wc <- &eventDataCall:
+ default:
+ }
}
})
--
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