mirrord for CI

How to use mirrord in a CI environment with `mirrord ci` commands.

mirrord can be used to greatly speed up CI runs by enabling testing against a shared staging environment without interrupting it. With mirrord for CI, you're able to keep your staging environment working, while also running your batch of end-to-end and other automated tests. The local app runs in the context of the targeted app that's deployed in your staging cluster, so it gets access to traffic, files, and more, as if it's running in the cluster. This means there's no need to spin up a whole test environment for a CI run, then spin it down when it's done.

While running regular mirrord exec can be made to work for this purpose, it requires some finagling to get right, such as wrapping mirrord exec in some other command that would start it as a background process. The mirrord ci start command is more appropriate for this use case, since it starts your app and mirrord as background processes, allowing you to then run tests while your app is running in the background and connected to the cluster.

You can only have one mirrord CI session per service during a CI run. You must do one mirrord ci start, run your tests, then run mirrord ci stop when they're done, before you're able to run mirrord ci start again in the same CI run.

Prerequisites

1. Minimum mirrord CLI version 3.166.0.

2. The CI runner must be able to access the Kubernetes cluster in which you want to test.

Kubernetes requirements

The CI runner must be able to access the Kubernetes cluster where the service you want to target is deployed, otherwise mirrord won't work. You'll need a kubeconfig in the CI runner that points to the target's cluster, and has the appropriate authentication.

It's recommended that you create a Kubernetes service account for the CI runner.

For mirrord for Teams users

To use mirrord ci with mirrord Operator, you'll need to generate a CI API key and store it as a secret environment variable. This will prevent your usage of mirrord in CI from expending your seats, which are counted using a machine-based ID.

You can get this key by running the command:

mirrord ci api-key

Copy it and save it as the secret environment variable MIRRORD_CI_API_KEY in your CI.

Starting a mirrord CI session

The mirrord ci start command functions very much like the mirrord exec command, meaning that it can take the same arguments, such as using a configuration file with --config-file, setting a target with --target, etc.

To view the entire list of arguments, run mirrord ci start --help.

• An example of starting a mirrord for CI session with npm run (you can run anything, it's not limited to npm):

mirrord ci start --target deployment/ip-visit-counter npm run

The mirrord for CI session should now be running in the background, and you can run the tests. These tests should target the deployed service (the app running in your staging cluster, for example), and mirrord will intercept the traffic and redirect it to the local app (the one running in the background in the CI runner with mirrord).

Application logs

By default, stdout and stderr outputs from your application are saved to a file in the OS' temporary directory (e.g. /tmp/mirrord). A directory is created based on the name of the binary you're running with mirrord, for example:

mirrord ci start --target deployment/ip-visit-counter npm run

# /tmp/mirrord/npm-{unique run identifier}

You can change this directory with the config ci.output_dir:

{
  "ci": {
    "output_dir": "/var/opt/mirrord"
  }
}

When running mirrord ci start --config-file mirrord.json, stdout and stderr outputs will be saved in the specified directory, e.g.:

mirrord ci start --config-file mirrord.json npm run

# /var/opt/mirrord/npm-{unique run identifier}

Stopping a mirrord CI session

After the tests are done, you should stop the mirrord CI session using mirrord ci stop. It's recommended that you do it, even if you won't be running mirrord for another service in this CI runner.

• Stopping a mirrord CI session:

mirrord ci stop

mirrord will stop running itself, and the local app.