Using MockServer in CircleCI builds

I have written some curl commands and wanted to verify that they are working as expected.

I am using MockServer to have a flexible server where I can define the expected requests and verify that the curl commands are working correctly.

MockServer as docker image.

The MockServer project produces docker images available on docker-hub.

The CircleCI docker executor

It is possible to execute builds inside docker containers, using the Docker Executor Type.

CircleCI provides also a way to define multiple images: the steps will be executed in the first container in the list (primary container) and all the tools and the exposed port provided by the other containers are available on localhost in the primary container.

The setup is clear:

• The primary container must be started from an image that contains curl. The CircleCI base image cimg/base:2020.01 can be used.
• The MockServer image will be a secondary container.

version: 2
jobs:
  build:
    docker:
      # Primary container: the steps will be executed in this container
      - image: cimg/base:2020.01 
      # MockServer as secondary container
      - image: mockserver/mockserver:mockserver-5.9.0

    steps:
      - run:
          name: Curl test
          # TODO: do something real instead of this placeholder command
          command: |
            curl --request PUT "http://localhost:1080/mockserver/reset"

Connection refused issue

There is an issue with this setup. The “Curl test” step is failing:

#!/bin/bash -eo pipefail
curl --request PUT "http://localhost:1080/mockserver/reset"

curl: (7) Failed to connect to localhost port 1080: Connection refused

Exited with code exit status 7

CircleCI received exit code 7

Some clue can be found in the “Container mockserver/mockserver:mockserver-5.9.0” log section:

java  -Dfile.encoding=UTF-8 -jar /opt/mockserver/mockserver-netty-jar-with-dependencies.jar  -serverPort 1080 -logLevel INFO &



Build was canceled

Even if MockServer is starting quickly thanks to the usage of Netty, the CircleCI executor does not wait enough.

Waiting until MockServer is ready

A trivial fix is to add a sleep step:

    steps:
      - run:
          name: Wait 30 seconds
          command: sleep 30

      - run:
          name: Curl test
          # TODO: do something real instead of this placeholder command
          command: |
            curl --request PUT "http://localhost:1080/mockserver/reset"

A better solution is to use curl with the --retry flag in order to wait until the MockServer reset call can be performed. Because at the beginning the connection is refused, we need to add --retry-connrefused to tell curl to continue to try to execute the call even if the first errors are “Connection refused” ones.

The first step becomes:

    steps:
      - run:
          name: Wait for MockServer
          command: |
            curl --retry 30 --retry-delay 2 --retry-connrefused --request PUT "http://localhost:1080/mockserver/reset"

      - run:
          name: Curl test
          # TODO: do something real instead of this placeholder command
          command: |
            curl --request PUT "http://localhost:1080/mockserver/reset"

The complete example will be published soon. I will update this page as soon as the repository is online.