From 284dcfdd144bef2accd6d72a6189041c9c63bb16 Mon Sep 17 00:00:00 2001
From: Silas Davis <silas@erisindustries.com>
Date: Fri, 9 Sep 2016 15:50:28 +0100
Subject: [PATCH] Fix blocking event subscription in transactAndHold
---
erisdb/pipe/transactor.go | 17 +++++++++++++++--
1 file changed, 15 insertions(+), 2 deletions(-)
diff --git a/erisdb/pipe/transactor.go b/erisdb/pipe/transactor.go
index c406d9c6..23f6a000 100644
--- a/erisdb/pipe/transactor.go
+++ b/erisdb/pipe/transactor.go
@@ -177,12 +177,25 @@ func (this *transactor) TransactAndHold(privKey, address, data []byte, gasLimit,
} else {
addr = address
}
- wc := make(chan *types.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 *types.EventDataCall, 1)
+
subId := fmt.Sprintf("%X", rec.TxHash)
this.eventEmitter.Subscribe(subId, types.EventStringAccCall(addr), func(evt types.EventData) {
event := evt.(types.EventDataCall)
if bytes.Equal(event.TxID, rec.TxHash) {
- wc <- &event
+ // 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 receive.
+ 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 <- &event:
+ default:
+ }
}
})
--
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