Add healthcheck.

Author: Dave Barnum

Dockerfile

@@ -3,20 +3,21 @@ MAINTAINER [email protected]
 
 RUN apt-get update && apt-get upgrade -y \
     && rm -rf /var/lib/apt/lists/*
-    
-COPY ["scripts/", "/docker-entrypoint-initdb.d/"]  
-COPY ["bin/initialize.sh", "bin/preflight.sh", "bin/persistence-cleanup.sh", "/usr/local/bin/"]
-RUN chmod 755 /usr/local/bin/persistence-cleanup.sh; \
+
+COPY ["scripts/", "/docker-entrypoint-initdb.d/"]
+COPY ["bin/initialize.sh", "bin/preflight.sh", "bin/docker-healthcheck", "bin/persistence-cleanup.sh", "/usr/local/bin/"]
+RUN chmod 755 /usr/local/bin/docker-healthcheck; \
+    chmod 755 /usr/local/bin/persistence-cleanup.sh; \
     chmod 755 /usr/local/bin/initialize.sh; \
-	chmod 755 /usr/local/bin/preflight.sh; \
+    chmod 755 /usr/local/bin/preflight.sh; \
     sed -i '/bin\/bash/a /usr/local/bin/initialize.sh' /usr/local/bin/docker-entrypoint.sh; \
-	sed -i '/exec "$@"/i /usr/local/bin/preflight.sh' /usr/local/bin/docker-entrypoint.sh
+    sed -i '/exec "$@"/i /usr/local/bin/preflight.sh' /usr/local/bin/docker-entrypoint.sh
 
 # we need to touch and chown config files, since we cant write as mysql user
 RUN touch /etc/mysql/conf.d/galera.cnf \
     touch /etc/mysql/conf.d/cust.cnf \
     && chown mysql.mysql /etc/mysql/conf.d/galera.cnf \
-	&& chown mysql.mysql /etc/mysql/conf.d/cust.cnf \
+    && chown mysql.mysql /etc/mysql/conf.d/cust.cnf \
     && chown mysql.mysql /docker-entrypoint-initdb.d/*.sql
 
 # we expose all Cluster related Ports
@@ -30,6 +31,8 @@ EXPOSE 3306 4444 4567 4568
 ENV GALERA_USER=galera \
     GALERA_PASS=galerapass \
     MAXSCALE_USER=maxscale \
-    MAXSCALE_PASS=maxscalepass \ 
+    MAXSCALE_PASS=maxscalepass \
     CLUSTER_NAME=docker_cluster \
-    MYSQL_ALLOW_EMPTY_PASSWORD=1
+    MYSQL_ALLOW_EMPTY_PASSWORD=1
+
+HEALTHCHECK CMD ["docker-healthcheck"]

bin/docker-healthcheck

@@ -0,0 +1,27 @@
+#!/bin/bash
+set -eo pipefail
+
+if [ "$MYSQL_RANDOM_ROOT_PASSWORD" ] && [ -z "$MYSQL_USER" ] && [ -z "$MYSQL_PASSWORD" ]; then
+	# there's no way we can guess what the random MySQL password was
+	echo >&2 'healthcheck error: cannot determine random root password (and MYSQL_USER and MYSQL_PASSWORD were not set)'
+	exit 0
+fi
+
+host="$(hostname --ip-address || echo '127.0.0.1')"
+user="${MYSQL_USER:-root}"
+export MYSQL_PWD="${MYSQL_PASSWORD:-$MYSQL_ROOT_PASSWORD}"
+
+args=(
+	# force mysql to not use the local "mysqld.sock" (test "external" connectibility)
+	-h"$host"
+	-u"$user"
+	--silent
+)
+
+if select="$(echo 'SELECT 1' | mysql "${args[@]}")" && [ "$select" = '1' ]; then
+	exit 0
+fi
+
+# If the probe returns 2 ("starting") when the container has already moved out of the "starting" state then it is treated as "unhealthy" instead.
+# https://github.com/docker/docker/blob/dcc65376bac8e73bb5930fce4cddc2350bb7baa2/docs/reference/builder.md#healthcheck
+exit 2