integrated startup sequence controlled by netcat

base/Dockerfile

@@ -6,7 +6,7 @@ RUN echo "deb http://ftp.debian.org/debian jessie-backports main" >> /etc/apt/so
 RUN apt-get update && DEBIAN_FRONTEND=noninteractive apt-get install -t jessie-backports -y --no-install-recommends openjdk-8-jdk
 ENV JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64/
 
-RUN apt-get update && DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends net-tools curl
+RUN apt-get update && DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends net-tools curl netcat
 
 RUN gpg --keyserver pool.sks-keyservers.net --recv-keys \
     07617D4968B34D8F13D56E20BE5AAA0BA210C095 \
@@ -40,7 +40,7 @@ RUN gpg --keyserver pool.sks-keyservers.net --recv-keys \
     0445B7BFC4515847C157ECD16BA72FF1C99785DE \
     B74F188889D159F3D7E64A7F348C6D7A0DCED714 \
     4A6AC5C675B6155682729C9E08D51A0A7501105C \
-    8B44A05C308955D191956559A5CEE20A90348D47 
+    8B44A05C308955D191956559A5CEE20A90348D47
 
 RUN gpg --keyserver pool.sks-keyservers.net --recv-key C36C5F0F
 
@@ -52,7 +52,7 @@ RUN set -x \
     && gpg --verify /tmp/hadoop.tar.gz.asc \
     && tar -xvf /tmp/hadoop.tar.gz -C /opt/ \
     && rm /tmp/hadoop.tar.gz*
-    
+
 RUN ln -s /opt/hadoop-$HADOOP_VERSION/etc/hadoop /etc/hadoop
 RUN cp /etc/hadoop/mapred-site.xml.template /etc/hadoop/mapred-site.xml
 RUN mkdir /opt/hadoop-$HADOOP_VERSION/logs

base/entrypoint.sh

@@ -79,4 +79,39 @@ if [ -n "$GANGLIA_HOST" ]; then
     done > /etc/hadoop/hadoop-metrics2.properties
 fi
 
+function wait_for_it()
+{
+    local serviceport=$1
+    local service=${serviceport%%:*}
+    local port=${serviceport#*:}
+    local retry_seconds=5
+    local max_try=100
+    let i=1
+
+    nc -z $service $port
+    result=$?
+
+    until [ $result -eq 0 ]; do
+      echo "[$i/$max_try] check for ${service}:${port}..."
+      echo "[$i/$max_try] ${service}:${port} is not available yet"
+      if (( $i == $max_try )); then
+        echo "[$i/$max_try] ${service}:${port} is still not available; giving up after ${max_try} tries. :/"
+        exit 1
+      fi
+      
+      echo "[$i/$max_try] try in ${retry_seconds}s once again ..."
+      let "i++"
+      sleep $retry_seconds
+
+      nc -z $service $port
+      result=$?
+    done
+    echo "[$i/$max_try] $service:${port} is available."
+}
+
+for i in "${SERVICE_PRECONDITION[@]}"
+do
+    wait_for_it ${i}
+done
+
 exec $@