Merge pull request #515 from thaJeztah/18.03-backport-election

[18.03] Increase raft ElectionTick to 10xHeartbeatTick

components/engine/daemon/cluster/noderunner.go

@@ -122,10 +122,13 @@ func (n *nodeRunner) start(conf nodeStartConfig) error {
 		JoinToken:          conf.joinToken,
 		Executor:           container.NewExecutor(n.cluster.config.Backend, n.cluster.config.PluginBackend),
 		HeartbeatTick:      1,
-		ElectionTick:       3,
-		UnlockKey:          conf.lockKey,
-		AutoLockManagers:   conf.autolock,
-		PluginGetter:       n.cluster.config.Backend.PluginGetter(),
+		// Recommended value in etcd/raft is 10 x (HeartbeatTick).
+		// Lower values were seen to have caused instability because of
+		// frequent leader elections when running on flakey networks.
+		ElectionTick:     10,
+		UnlockKey:        conf.lockKey,
+		AutoLockManagers: conf.autolock,
+		PluginGetter:     n.cluster.config.Backend.PluginGetter(),
 	}
 	if conf.availability != "" {
 		avail, ok := swarmapi.NodeSpec_Availability_value[strings.ToUpper(string(conf.availability))]