integrated startup sequence controlled by netcat

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 $@