cogito

README

cogito

Cogito (Concourse git status resource) is a Concourse resource to update the GitHub status of a commit during a build. The name is a humble homage to René Descartes.

Written in Go, it has the following characteristics:

• As lightweight as possible (Docker Alpine image).
• Extensive test suite.
• Autodiscovery of configuration parameters.
• No assumptions on the git repository (for example, doesn't assume that the default branch is main or that branch main even exists).
• Helpful error messages when something goes wrong with the GitHub API.
• Configurable logging for the three steps (check, in, out) to help troubleshooting.
• Boilerplate code generated with ofcourse.

Contributing and Development

This document explains how to use this resource. See CONTRIBUTING for how to build the Docker image, develop, test and contribute to this resource.

Semver, releases and Docker images

This project follows Semantic Versioning and has a CHANGELOG.

NOTE Following semver, no backwards compatibility is guaranteed as long as the major version is 0.

Releases are tagged in the git repository with the semver format vMAJOR.MINOR.PATCH (note the v prefix). The corresponding Docker image has tag MAJOR.MINOR.PATCH and is available from DockerHub.

Which Docker tag to use?

• The latest tag always points to the latest release, not to the tip of master, so it is quite stable.
• Alternatively, you can pin the resource to a specific release tag MAJOR.MINOR.PATCH.

Example

See also pipelines/cogito.yml for a bigger example and for how to use YAML anchors to reduce as much as possible YAML verbosity.

resource_types:
- name: cogito
  type: registry-image
  check_every: 1h
  source:
    repository: pix4d/cogito

resources:
- name: gh-status
  type: cogito
  check_every: 1h
  source:
    owner: ((your-github-user-or-organization))
    repo: ((your-repo-name))
    access_token: ((your-OAuth-personal-access-token))

- name: the-repo
  type: git
  source:
    uri: https://github.com/((your-github-user-or-organization))/((your-repo-name))
    branch: ((branch))

jobs:
  - name: autocat
    on_success:
      put: gh-status
      inputs: [the-repo]
      params: {state: success}
    on_failure:
      put: gh-status
      inputs: [the-repo]
      params: {state: failure}
    on_error:
      put: gh-status
      inputs: [the-repo]
      params: {state: error}
    plan:
      - get: the-repo
        trigger: true
      - put: gh-status
        inputs: [the-repo]
        params: {state: pending}
      - task: maybe-fail
        config:
          platform: linux
          image_resource:
            type: registry-image
            source: { repository: alpine }
          run:
            path: /bin/sh
            args:
              - -c
              - |
                set -o errexit
                echo "Hello world!"

Effects on GitHub

With reference to the GitHub status API, the POST parameters (state, target_url, description, context) are set by Cogito and rendered by GitHub as follows:

Source Configuration

Required

• owner: The GitHub user or organization.
• repo: The GitHub repository name.
• access-token: The OAuth access token. See section GitHub OAuth token.

Optional

• context_prefix: The prefix for the context (see section Effects on GitHub). If present, the context will be context_prefix/job_name. Default: empty. See also the optional context in the put step.
• log_level: The log level (one of debug, info, warn, error, silent). Default: info.
• log_url. A Google Hangout Chat webhook. Useful to obtain logging for the check step for Concourse < 7.

Suggestions

We suggest to set a long interval for check_interval, for example 1 hour, as shown in the example above. This helps to reduce the number of check containers in a busy Concourse deployment and, for this resource, has no adverse effects.

The check step

It is currently a no-op and will always return the same version, dummy.

The get step

It is currently a no-op.

The put step

Sets or updates the GitHub status for a given commit, following the GitHub status API.

Required

• state: The state to set. One of error, failure, pending, success.

Optional:

• context: The value of the non-prefix part of the context (see section Effects on GitHub). Default: job_name. See also the optional context_prefix in the source configuration.

Note

The put step requires one and only one "put inputs" to be specified, otherwise it will error out. For example:

on_success:
  put: gh-status
  # This is the name of the git resource corresponding to the GitHub repo to be updated.
  inputs: [the-repo]
  params: {state: success}

As all the other GitHub status resources, it requires as input the git repo passed by the git resource because it will look inside it to gather information such as the commit hash for which to set the status.

It requires only one put input to help you have an efficient pipeline, since if the "put inputs" list is not set explicitly, Concourse will stream all inputs used by the job to this resource, which can have a big performance impact. From the "put inputs" documentation:

inputs: [string]

Optional. If specified, only the listed artifacts will be provided to the container. If not specified, all artifacts will be provided.

To better understand from where the-repo comes from, see the full example at the beginning of this document.

GitHub OAuth token

Follow the instructions at GitHub personal access token to create a personal access token.

Give to it the absolute minimum permissions to get the job done. This resource only needs the repo:status scope, as explained at GitHub status API.

NOTE: The token is security-sensitive. Treat it as you would treat a password. Do not encode it in the pipeline YAML and do not store it in a YAML file. Use one of the Concourse-supported credentials managers, see Concourse credential managers.

See also the section The end-to-end tests for how to securely store the token to run the end-to-end tests.

Caveat: GitHub rate limiting

From GitHub API v3

Rate limiting

For API requests using Basic Authentication or OAuth, you can make up to 5000 requests per hour. All OAuth applications authorized by a user share the same quota of 5000 requests per hour when they authenticate with different tokens owned by the same user.

For unauthenticated requests, the rate limit allows for up to 60 requests per hour. Unauthenticated requests are associated with the originating IP address, and not the user making requests.

In case of rate limiting, the error message in the output of the put step will mention it.

License

This code is licensed according to the MIT license (see file LICENSE).