Running Docker image of Postman from Gitlab CI pipeline

Question

I want to run a Postman collection from a Docker image in a Gitlab CI pipeline. The Docker socket file is already mounted for the gitlab-ci-runner so the runner has access to the docker server.

Here's the job definition from .gitlab-ci.yaml

postman:
    image: docker:20.10.14
    stage: schedule
    only: 
        - schedules
    before_script: []
    script:
        - env
        - docker run -t -v $CI_PROJECT_DIR:/etc/newman postman/newman run postman_collection.json

The console output of the gitlab CI runner looks like this:

    $ docker run -t -v $CI_PROJECT_DIR:/etc/newman postman/newman run postman_collection.json
error: collection could not be loaded
  unable to read data from file "postman_collection.json"
  ENOENT: no such file or directory, open 'postman_collection.json'

The file exists. I even tried

 docker run --rm -it -v $PWD:/etc/newman --entrypoint sh postman/newman

from my localhost console and ran it manually. It's all there. What am I missing?

List item

sytech · Accepted Answer · 2022-09-08T17:04:55.800

The Docker socket file is already mounted for the gitlab-ci-runner

The problem here is that in the scenario where you are talking to the host docker daemon (i.e., when the host docker socket in mounted in the job), when you pass the volume argument to docker run like -v /source/path:/container/path the /source/path part of the argument refers to the host filesystem not the filesystem of the job container.

Think about it like this: the host docker daemon doesn't know that its socket is mounted inside the job container. So when you run docker commands this way, it's as if you're running the docker command on the runner host!

Because $PWD and $CI_PROJECT_DIR in your job command evaluates to a path in the job container (and this path isn't on the runner host filesystem) the volume mount will not work as expected.

This limitation is noted in the limitations of Docker socket binding documentation:

Sharing files and directories from the source repository into containers may not work as expected. Volume mounting is done in the context of the host machine, not the build container

The easiest workaround here would likely be to use postman/newman as your image: instead of docker.

myjob:
  image: 
    name: postman/newman
    entrypoint: [""]

  script:
    - newman run postman_collection.json

That was extremely helpful! Thank you. Please indulge one more question for my understanding: Why do I need to override the entrypoint and then add "newman ..." to the script? The entrypoint in the image is already "newman". Why won't the script "run ..." work? — Lawrence I. Siden, Sep 12 '22 at 17:30
@LawrenceI.Siden glad this was helpful for you. Regarding the `entrypoint`, basically this is required because of how GitLab passes job scripts to the job container (and therefore how images are expected to receive and execute scripts -- specifically, images are expected to read scripts from `stdin` and do not get arguments to the entrypoint). This is partly explained [in the docs](https://docs.gitlab.com/ee/ci/docker/using_docker_images.html#override-the-entrypoint-of-an-image). — sytech, Sep 12 '22 at 18:07

Running Docker image of Postman from Gitlab CI pipeline

1 Answers1