From 3bea5124cbacc9dc45a000ea66a982f4492a65b5 Mon Sep 17 00:00:00 2001
From: Madhu Venugopal <madhu@docker.com>
Date: Thu, 1 Oct 2015 21:50:54 -0700
Subject: [PATCH] serfJoin doesnt happen if self notification comes later

With the recently introduced docker discovery, the self node discovery
notification can reach the overlay driver after the remote node
discovery notification.  In scenarios such as 2 node setup, it seems more
likely. In those scenarios, the serfJoin is not triggered and hence the
neighborship is not formed between the 2 nodes.

The fix is to retain the knowledge of the neighbor and reuse it
immediately after the serfInit is done. Since we do the serfJoin just
once, there is no harm in changing the neighIP to a new value even if it
is not used.

Signed-off-by: Madhu Venugopal <madhu@docker.com>
---
 drivers/overlay/ov_serf.go |  8 ++++----
 drivers/overlay/overlay.go | 18 +++++++++++-------
 2 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/drivers/overlay/ov_serf.go b/drivers/overlay/ov_serf.go
index cac97ae..d717c10 100644
--- a/drivers/overlay/ov_serf.go
+++ b/drivers/overlay/ov_serf.go
@@ -68,13 +68,13 @@ func (d *driver) serfInit() error {
 	return nil
 }
 
-func (d *driver) serfJoin() error {
-	if d.neighIP == "" {
+func (d *driver) serfJoin(neighIP string) error {
+	if neighIP == "" {
 		return fmt.Errorf("no neighbor to join")
 	}
-	if _, err := d.serfInstance.Join([]string{d.neighIP}, false); err != nil {
+	if _, err := d.serfInstance.Join([]string{neighIP}, false); err != nil {
 		return fmt.Errorf("Failed to join the cluster at neigh IP %s: %v",
-			d.neighIP, err)
+			neighIP, err)
 	}
 	return nil
 }
diff --git a/drivers/overlay/overlay.go b/drivers/overlay/overlay.go
index ff29c8d..c4cbbb6 100644
--- a/drivers/overlay/overlay.go
+++ b/drivers/overlay/overlay.go
@@ -152,7 +152,7 @@ func (d *driver) Type() string {
 }
 
 func (d *driver) nodeJoin(node string, self bool) {
-	if self && node != "" && !d.isSerfAlive() {
+	if self && !d.isSerfAlive() {
 		d.Lock()
 		d.bindAddress = node
 		d.Unlock()
@@ -163,13 +163,17 @@ func (d *driver) nodeJoin(node string, self bool) {
 		}
 	}
 
-	if d.serfInstance != nil && !self && node != "" {
+	d.Lock()
+	if !self {
+		d.neighIP = node
+	}
+	neighIP := d.neighIP
+	d.Unlock()
+
+	if d.serfInstance != nil && neighIP != "" {
 		var err error
 		d.joinOnce.Do(func() {
-			d.Lock()
-			d.neighIP = node
-			d.Unlock()
-			err = d.serfJoin()
+			err = d.serfJoin(neighIP)
 		})
 		if err != nil {
 			logrus.Errorf("joining serf neighbor %s failed: %v", node, err)
@@ -185,7 +189,7 @@ func (d *driver) nodeJoin(node string, self bool) {
 func (d *driver) DiscoverNew(dType driverapi.DiscoveryType, data interface{}) error {
 	if dType == driverapi.NodeDiscovery {
 		nodeData, ok := data.(driverapi.NodeDiscoveryData)
-		if !ok {
+		if !ok || nodeData.Address == "" {
 			return fmt.Errorf("invalid discovery data")
 		}
 		d.nodeJoin(nodeData.Address, nodeData.Self)