[es] Add support for Swarm Mode with proper transport publish computation

elasticsearch/README.md

@@ -169,3 +169,15 @@ The minimum, which can be calculated as `(master_eligible_nodes / 2) + 1`, can b
 Using the Docker Compose file above, a value of `2` is appropriate when scaling the cluster to 3 master nodes:
 
     docker-compose scale master=3
+
+## Auto transport discovery with Swarm Mode
+
+When using Docker Swarm mode (starting with 1.12), the overlay and ingress network interfaces are assigned
+multiple IP addresses. As a result, it creates confusion for the transport publish logic even when using
+the special value `_eth0_`.
+
+To resolve this, add
+
+    -e DISCOVER_TRANSPORT_IP=eth0
+
+replacing `eth0` with another interface within the container, if needed.

elasticsearch/start

@@ -18,6 +18,12 @@ OPTS="$OPTS -Des.path.conf=/conf \
   -Des.transport.tcp.port=9300 \
   -Des.http.port=9200"
 
+if [ "$DISCOVER_TRANSPORT_IP" != "" ]; then
+  ip=`ipaddr show dev $DISCOVER_TRANSPORT_IP scope global|awk '$1 == "inet" { if (!match($2,"/32")) { gsub("/.*","",$2) ; print $2 } }'`
+  echo "Discovered address $ip for $DISCOVER_TRANSPORT_IP"
+  OPTS="$OPTS -Des.transport.host=$ip"
+fi
+
 if [ -n "$CLUSTER" ]; then
   OPTS="$OPTS -Des.cluster.name=$CLUSTER"
   if [ -n "$CLUSTER_FROM" ]; then