From e49a29197b6719d347aaa1566108b6e99177e3a6 Mon Sep 17 00:00:00 2001
From: Bryan Boreham <bjboreham@gmail.com>
Date: Mon, 15 Jun 2015 13:48:24 +0100
Subject: [PATCH] Add a Flush() routine to synchronize callers

---
 common/sched_queue.go | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/common/sched_queue.go b/common/sched_queue.go
index e5ed0667..7e7c9f44 100644
--- a/common/sched_queue.go
+++ b/common/sched_queue.go
@@ -142,3 +142,15 @@ func (cq *SchedQueue) durationUntilNext(now time.Time) time.Duration {
 	}
 	return time.Duration(math.MaxInt64)
 }
+
+// ensure that the background goroutine has executed any pending callbacks
+func (cq *SchedQueue) Flush() {
+	ch := make(chan struct{})
+	flushFunc := func() time.Time {
+		atomic.AddUint64(&cq.counter, ^uint64(0)) // decrement so nobody sees this
+		close(ch)
+		return time.Time{}
+	}
+	cq.schedChan <- &schedCall{c: flushFunc, t: time.Time{}}
+	<-ch
+}