test:
  image: docker
  stage: test
  services:
    - docker:dind
  script:
    - APP_CONTAINER_ID=`docker run -d --privileged -p "9143:9143" appropriate/nc nc -l 9143`
    - netstat -a
    - docker exec $APP_CONTAINER_ID netstat -a
    - nc -v localhost 9143

gitlab-ci-multi-runner exec docker --docker-privileged test

$ netstat -a
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State
tcp        0      0 runner--project-1-concurrent-0:54664 docker:2375             TIME_WAIT
tcp        0      0 runner--project-1-concurrent-0:54666 docker:2375             TIME_WAIT
Active UNIX domain sockets (servers and established)
Proto RefCnt Flags       Type       State         I-Node Path

$ docker exec $APP_CONTAINER_ID netstat -a
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State
tcp        0      0 0.0.0.0:9143            0.0.0.0:*               LISTEN
Active UNIX domain sockets (servers and established)
Proto RefCnt Flags       Type       State         I-Node Path

$ nc -v localhost 9143
ERROR: Build failed: exit code 1
FATAL: exit code 1

test:
  image: craigotis/buildtools:v1
  stage: test
  script:
    - docker login -u gitlab-ci-token -p $CI_BUILD_TOKEN registry.gitlab.com/craigotis/myapp
    - docker-compose up -d
    - sleep 60 # a temporary hack to get the logs
    - docker-compose logs
    - docker-machine env
    - docker-compose port app 9143
    - netstat -a
    - docker-compose ps
    - /usr/local/bin/wait-for-it.sh -h localhost -p 9143 -t 60
    - cd mocha
    - npm i
    - npm test
    - docker-compose down

$ docker-compose logs
...
app_1  | [Thread-1] INFO spark.webserver.SparkServer - == Spark has ignited ...
app_1  | [Thread-1] INFO spark.webserver.SparkServer - >> Listening on 0.0.0.0:9143
app_1  | [Thread-1] INFO org.eclipse.jetty.server.Server - jetty-9.0.z-SNAPSHOT
app_1  | [Thread-1] INFO org.eclipse.jetty.server.ServerConnector - Started ServerConnector@6919dc5{HTTP/1.1}{0.0.0.0:9143}
...

$ docker-compose port app 9143
0.0.0.0:9143

$ netstat -a
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State
tcp        0      0 runner-e11ae361-project-1925166-concurrent-0:53646 docker:2375             TIME_WAIT
tcp        0      0 runner-e11ae361-project-1925166-concurrent-0:53644 docker:2375             TIME_WAIT
tcp        0      0 runner-e11ae361-project-1925166-concurrent-0:53642 docker:2375             TIME_WAIT
Active UNIX domain sockets (servers and established)
Proto RefCnt Flags       Type       State         I-Node Path

$ docker-compose ps
stty: standard input: Not a tty
    Name                  Command               State                Ports
----------------------------------------------------------------------------------------
my_app_1   wait-for-it.sh mysql_serve ...   Up      8080/tcp, 0.0.0.0:9143->9143/tcp
mysql_server   docker-entrypoint.sh --cha ...   Up      3306/tcp

$ /usr/local/bin/wait-for-it.sh -h localhost -p 9143 -t 60
wait-for-it.sh: waiting 60 seconds for localhost:9143
wait-for-it.sh: timeout occurred after waiting 60 seconds for localhost:9143

version: '2'

networks:
    app_net:
        driver: bridge

services:
    app:
        image: registry.gitlab.com/craigotis/myapp:latest
        depends_on:
        - "db"
        networks:
        - app_net
        command: wait-for-it.sh mysql_server:3306 -t 60 -- java -jar /opt/app*.jar
        ports:
        - "9143:9143"

    db:
        image: mysql:latest
        networks:
        - app_net
        container_name: mysql_server
        environment:
        - MYSQL_ALLOW_EMPTY_PASSWORD=true

127.0.0.1 is the loopback address (also known as localhost).
0.0.0.0 is a non-routable meta-address used to designate an invalid, unknown, or non-applicable target (a ‘no particular address’ place holder).