Setting up an Image Repository in Dispatch

This is a follow-up guide to setting up a Repository that walks through setting up an ImageRepository in Dispatch. ImageRepository can be used to monitor a Docker registry and trigger Pipelines based on Image related events.

An ImageRepository resource can be created using CLI command dispatch ci image-repository create <...>. An ImageRepository resource is responsible for creating webhooks on a given Docker Registry Image Repository and triggering pipelines based on the events received from the Docker registry webhook.

Prerequisites

This tutorial assumes that you have done the following:

• Installed Dispatch
• Set up a Repository in Dispatch that has a valid Dispatchfile hosting tasks to run on Docker related events
• Set up access to a valid Docker repository with sufficient authentication to manage webhooks.

Setting up a Dispatchfile in Repository with Docker image related actions

Consider the following Dispatchfile that has a task named test that triggers on every push to image with tags matching ["release"]:

#!mesosphere/dispatch-cue:v0.7
resource "src-git": {
  type: "git"
  param url: "$(context.git.url)"
  param revision: "$(context.git.commit)"
}

task "test": {
  inputs: ["src-git"]

  steps: [
    {
      name: "test"
      image: "golang:1.15.7-buster"
      command: [ "go", "test", "./..." ]
      workingDir: "/workspace/src-git"
    }
  ]
}

actions: [
  {
    tasks: ["test"]
    on image push: {
      tags: ["release"]
    }
  }
]

Currently, only push events from registries are supported. The tags field supports globbing and negative matching as well.

Setting up an ImageRepository

To configure Dispatch to listen to incoming Docker events, an ImageRepository resource needs to be created. This can be achieved by using the CLI command:

➜ dispatch ci image-repository create --help
Add an ImageRepository to Dispatch.

Usage:
  dispatch ci image-repository create [flags]

Flags:
      --dispatchfile-git-server string                      The Git server hosting the repository where the Dispatchfile resides. Defaults to the Git remote given by --remote, if the current directory is a Git repository.
      --dispatchfile-path string                            Override the default Dispatchfile path. (default "Dispatchfile")
      --dispatchfile-repository string                      Repository to fetch the Dispatchfile from
      --dispatchfile-repository-scm-secret string           SCM secret to use when fetching the Dispatchfile
      --dispatchfile-revision string                        Revision of Dispatchfile in SCM repo (default "master")
  -h, --help                                                help for create
      --image-repository string                             Set the Docker repository name.
      --image-repository-name string                        Name of the image repository to be created. Name is auto generated if empty.
      --image-repository-secret string                      Secret to use to create Docker webhooks
      --log-storage-rules LogStorageRules                   Json Array of rules specifying underlying log pruning rules.
                                                            Each element of array specifies three values:
                                                            - "maxBuildAge" (in days, minimum 1 day),
                                                            - "maxBuildRuns", and
                                                            - "tasks" (glob expr to match pipeline and tasks). E.g.:
                                                            [
                                                            	{"maxBuildAge": 30, "maxBuildRuns": 100, "tasks": "*"}, // Applies to entire pipeline
                                                            	{"maxBuildAge": 7, "maxBuildRuns": 200, "tasks": "unit-*"} // Applies to task(s) beginning with "unit-"
                                                            ] (default null)
      --pod-template-config-map-key string                  Set the key in ConfigMap to access the pod template (default "default-pod-template")
      --pod-template-config-map-name default-pod-template   Set the name of a ConfigMap containing a key named default-pod-template to override the globally defined pod template for this repository
      --pod-template-config-map-optional                    Specify whether the ConfigMap or its key must be defined (default true)
      --remote string                                       Git remote to look up Github repository from. (default "origin")
      --service-account string                              The service account name to use when creating pipelines.
      --timeout duration                                    Duration after which pipelines fail due to timeout. Default is to use the globally defined timeout.
      --url string                                          If set, uses this URL for the webhook URL instead of detecting from an Ingress rule.

Global Flags:
      --dry-run            Set to only print Tekton YAML but not apply it
  -n, --namespace string   Target namespace in the Kubernetes cluster to use (If empty, this is determined from kubeconfig)
  -o, --output string      Output format to use (default "yaml")

The following steps should be completed before creating an ImageRepository resource:

• Ensure that the namespace to be used exists.
• Esnure that you have set up scm credentials for the service account for Dispatch to access the source control management service on behalf of your account.
• Ensure that you have set up registry credentials for the service account for Dispatch to access the registry service on behalf of your account.

After a service account is created and scm and registry credentials are associated with it using dispatch ci login github and dispatch ci login Docker respectively, an ImageRepository resource can be created using:

dispatch ci image-repository create --service-account=<service-account> --image-repository <image-repository> --dispatchfile-repository=<dispatchfile-scm-repository>

It takes a few minutes for the ImageRepository to be reconciled which results in creation of webhooks on given Docker repository.