Healthcheck using Host and Port from zoo.cfg

Since it's getting more complex, I moved the healthcheck logic to its
own script.

Author: j3k0

Dockerfile

@@ -18,7 +18,8 @@ WORKDIR /opt/zookeeper
 
 # Only checks if server is up and listening, not quorum. 
 # See https://zookeeper.apache.org/doc/r3.4.13/zookeeperAdmin.html#sc_zkCommands
-HEALTHCHECK CMD [ $(echo ruok | nc 127.0.0.1:2181) == "imok" ] || exit 1
+COPY healthcheck /healthcheck
+HEALTHCHECK CMD /healthcheck
 
 VOLUME ["/opt/zookeeper/conf", "/tmp/zookeeper"]
 

healthcheck

@@ -0,0 +1,11 @@
+#!/bin/bash
+# Read bound host and port from the config file (if any)
+set -e
+
+CFG=/opt/zookeeper/conf/zoo.cfg
+if [ -e "$CFG" ]; then
+    H="$(awk -F= '/^clientPortAddress=/{ print $2 }' "$CFG")"
+    P="$(awk -F= '/^clientPort=/{ print $2 }' "$CFG")"
+fi
+
+[ "$(echo ruok | nc "${H:-127.0.01}" "${P:-2181}")" == "imok" ] || exit 1