X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/d258e5c5b361dcdf7d65d2791eb83bd31d72c86c..2a748e79c3a72454d70e40f39fcad9dabf4943cc:/lib/dispatchcloud/worker/pool.go

diff --git a/lib/dispatchcloud/worker/pool.go b/lib/dispatchcloud/worker/pool.go
index e81c2c091f..e90935e2aa 100644
--- a/lib/dispatchcloud/worker/pool.go
+++ b/lib/dispatchcloud/worker/pool.go
@@ -419,8 +419,12 @@ func (wp *Pool) Shutdown(it arvados.InstanceType) bool {
 }
 
 // CountWorkers returns the current number of workers in each state.
+//
+// CountWorkers blocks, if necessary, until the initial instance list
+// has been loaded from the cloud provider.
 func (wp *Pool) CountWorkers() map[State]int {
 	wp.setupOnce.Do(wp.setup)
+	wp.waitUntilLoaded()
 	wp.mtx.Lock()
 	defer wp.mtx.Unlock()
 	r := map[State]int{}
@@ -786,6 +790,7 @@ func (wp *Pool) sync(threshold time.Time, instances []cloud.Instance) {
 	}
 
 	if !wp.loaded {
+		notify = true
 		wp.loaded = true
 		wp.logger.WithField("N", len(wp.workers)).Info("loaded initial instance list")
 	}
@@ -795,6 +800,17 @@ func (wp *Pool) sync(threshold time.Time, instances []cloud.Instance) {
 	}
 }
 
+func (wp *Pool) waitUntilLoaded() {
+	ch := wp.Subscribe()
+	wp.mtx.RLock()
+	defer wp.mtx.RUnlock()
+	for !wp.loaded {
+		wp.mtx.RUnlock()
+		<-ch
+		wp.mtx.RLock()
+	}
+}
+
 // Return a random string of n hexadecimal digits (n*4 random bits). n
 // must be even.
 func randomHex(n int) string {