Push collector docker image when sky-walking released

.travis.yml

@@ -13,3 +13,4 @@ script:
 
 after_success:
   - mvn clean cobertura:cobertura coveralls:report
+  - bash ./travis/push_image.sh

travis/push_image.sh

@@ -0,0 +1,24 @@
+#!/bin/sh
+
+check_pull_is_release() {
+  if [ "${TRAVIS_TAG}" = "" ]; then
+    return 1
+  else
+    echo "[Pushing] pushing docker image of ${TRAVIS_TAG}."
+    return 0
+  fi
+
+}
+
+push_collector_image() {
+  docker login -u="$DOCKER_USERNAME" -p="$DOCKER_PASSWORD"
+  mvn clean package docker:build
+  docker push skywalking/skywalking-collector:latest
+  docker push skywalking/skywalking-collector:${TRAVIS_TAG}
+}
+
+
+if check_pull_is_release; then
+    push_collector_image
+    echo "[Pushing] push Done!"
+fi