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Version: Next

GitHub Discovery

info

This documentation is written for the new backend system which is the default since Backstage version 1.24. If you are still on the old backend system, you may want to read its own article instead, and consider migrating!

GitHub Provider​

The GitHub integration has a discovery provider for discovering catalog entities within a GitHub organization. The provider will crawl the GitHub organization and register entities matching the configured path. This can be useful as an alternative to static locations or manually adding things to the catalog. This is the preferred method for ingesting entities into the catalog.

Installation​

You will have to add the GitHub Entity provider to your backend as it is not installed by default, therefore you have to add a dependency on @backstage/plugin-catalog-backend-module-github to your backend package.

From your Backstage root directory
yarn --cwd packages/backend add @backstage/plugin-catalog-backend-module-github

And then update your backend by adding the following line:

packages/backend/src/index.ts
backend.add(import('@backstage/plugin-catalog-backend'));
backend.add(import('@backstage/plugin-catalog-backend-module-github'));

Events Support​

The catalog module for GitHub comes with events support enabled. This will make it subscribe to its relevant topics (github.push, github.repository) and expects these events to be published via the EventsService.

Prerequisites​

There are two Prerequisites to use the builtin events support:

  1. Creating a webhook in GitHub
  2. Installing and configuring @backstage/plugin-events-backend-module-github

Configure Webhooks in GitHub​

You can check the official docs to configure your webhook and to secure your request.

The webhook(s) will need to be configured to react to push and repository events.

note

To receive the repository.transferred event, the new owner account must have the GitHub App installed, and the App must be subscribed to repository events. This event is only sent to the account where the ownership is transferred.

When creating the webhook in GitHub the "Payload URL" will looks something along these lines: https://<your-intance-name>/api/events/http/github and the "Content Type" should be application/json.

The GitHub Webhooks UI will send a trial event to validate it can connect when you save your new Webhook. It is possible to retry this trial event if it fails and you want to send it again. Additionally there is a Recent Deliveries tab you can use to validate that the events are being fired should you need to do any later troubleshooting.

Install and Configure GitHub Events Module​

In order to use the built-in events support you'll need to install and configure @backstage/plugin-events-backend-module-github. This module will route received events from the generic topic github to more specific ones based on the event type (e.g., github.push). These more specific events are what the builtin events support is expecting.

First we need to add the package:

from your Backstage root directory
yarn --cwd packages/backend add @backstage/plugin-events-backend-module-github

Then we need to add it to your backend:

in packages/backend/src/index.ts
backend.add(import('@backstage/plugin-events-backend'));
backend.add(import('@backstage/plugin-events-backend-module-github'));

Finally you will want to configure it:

events:
  modules:
    github:
      webhookSecret: ${GITHUB_WEBHOOK_SECRET}

Though this last step is technically optional, you'll want to include it to be sure the events being received are from GitHub and not from an external bad actor.

The value of ${GITHUB_WEBHOOK_SECRET} in this example would be the same that you used when creating the webhook on GitHub.

Events Setup using HTTP endpoint​

Using the HTTP endpoint for events just requires adding some additional configuration to your app-config.yaml as it is a built in feature of the Events backend, here's what that would look like:

events:
  http:
    topics:
      - github

This will then expose an endpoint like this: http://localhost/api/events/http/github

Events Setup using AWS SQS module​

Alternatively to using the HTTP endpoint you can use the AWS SQS module, here's how.

First we need to add the package:

from your Backstage root directory
yarn --cwd packages/backend add @backstage/plugins-events-backend-module-aws-sqs

Then we need to add it to your backend:

in packages/backend/src/index.ts
backend.add(import('@backstage/plugin-events-backend'));
backend.add(import('@backstage/plugin-events-backend-module-github'));
backend.add(import('@backstage/plugins-events-backend-module-aws-sqs'));

Finally you will want to configure it:

events:
  modules:
    awsSqs:
      awsSqsConsumingEventPublisher:
        topics:
          github:
            queue:
              url: 'https://sqs.us-east-2.amazonaws.com/123456789012/MyQueue'
              region: us-east-2

The AWS SQS module README has more details on the configuration options, the example above includes on the required options.

Events Setup using Google Pub/Sub module​

Alternatively to using the HTTP endpoint you can use the Google Pub/Sub module, here's how.

First we need to add the package:

from your Backstage root directory
yarn --cwd packages/backend add @backstage/plugin-events-backend-module-google-pubsub

Then we need to add it to your backend:

in packages/backend/src/index.ts
backend.add(import('@backstage/plugin-events-backend'));
backend.add(import('@backstage/plugin-events-backend-module-github'));
backend.add(import('@backstage/plugin-events-backend-module-google-pubsub'));

Finally you will want to configure it:

events:
  modules:
    googlePubSub:
      googlePubSubConsumingEventPublisher:
        subscriptions:
          # A unique key for your subscription, to be used in logging and metrics
          mySubscription:
            # The fully qualified name of the subscription
            subscriptionName: 'projects/my-google-project/subscriptions/github-enterprise-events'
            # The event system topic to transfer to. This can also be just a plain string
            targetTopic: 'github.{{ event.attributes.x-github-event }}'

The Google Pub/Sub module README has more details on the configuration options, the example above includes on the required options.

Configuration​

To use the discovery provider, you'll need a GitHub integration set up with either a Personal Access Token or GitHub Apps. For Personal Access Tokens you should pay attention to the required scopes, where you will need at least the repo scope for reading components. For GitHub Apps you will need to grant it the required permissions instead, where you will need at least the Contents: Read-only permissions for reading components.

Then you can add a github config to the catalog providers configuration:

catalog:
  providers:
    github:
      # the provider ID can be any camelCase string
      providerId:
        organization: 'backstage' # string
        catalogPath: '/catalog-info.yaml' # string
        filters:
          branch: 'main' # string
          repository: '.*' # Regex
        schedule: # same options as in SchedulerServiceTaskScheduleDefinition
          # supports cron, ISO duration, "human duration" as used in code
          frequency: { minutes: 30 }
          # supports ISO duration, "human duration" as used in code
          timeout: { minutes: 3 }
      customProviderId:
        organization: 'new-org' # string
        catalogPath: '/custom/path/catalog-info.yaml' # string
        filters: # optional filters
          branch: 'develop' # optional string
          repository: '.*' # optional Regex
      wildcardProviderId:
        organization: 'new-org' # string
        catalogPath: '/groups/**/*.yaml' # this will search all folders for files that end in .yaml
        filters: # optional filters
          branch: 'develop' # optional string
          repository: '.*' # optional Regex
      topicProviderId:
        organization: 'backstage' # string
        catalogPath: '/catalog-info.yaml' # string
        filters:
          branch: 'main' # string
          repository: '.*' # Regex
          topic: 'backstage-exclude' # optional string
      topicFilterProviderId:
        organization: 'backstage' # string
        catalogPath: '/catalog-info.yaml' # string
        filters:
          branch: 'main' # string
          repository: '.*' # Regex
          topic:
            include: ['backstage-include'] # optional array of strings
            exclude: ['experiments'] # optional array of strings
      validateLocationsExist:
        organization: 'backstage' # string
        catalogPath: '/catalog-info.yaml' # string
        filters:
          branch: 'main' # string
          repository: '.*' # Regex
        validateLocationsExist: true # optional boolean
      visibilityProviderId:
        organization: 'backstage' # string
        catalogPath: '/catalog-info.yaml' # string
        filters:
          visibility:
            - public
            - internal
      enterpriseProviderId:
        host: ghe.example.net
        organization: 'backstage' # string
        catalogPath: '/catalog-info.yaml' # string

This provider supports multiple organizations via unique provider IDs.

Note

It is possible but certainly not recommended to skip the provider ID level. If you do so, default will be used as provider ID.

  • catalogPath (optional): Default: /catalog-info.yaml. Path where to look for catalog-info.yaml files. You can use wildcards - *, ** or a glob pattern supported by minimatch - to search the path and/or the filename. Wildcards cannot be used if the validateLocationsExist option is set to true.
  • filters (optional):
    • branch (optional): String used to filter results based on the branch name. Branch name cannot have any slash (/) characters. Defaults to the default Branch of the repository.
    • repository (optional): Regular expression used to filter results based on the repository name.
    • topic (optional): Both of the filters below may be used at the same time but the exclusion filter has the highest priority. In the example above, a repository with the backstage-include topic would still be excluded if it were also carrying the experiments topic.
      • include (optional): An array of strings used to filter in results based on their associated GitHub topics. If configured, only repositories with one (or more) topic(s) present in the inclusion filter will be ingested
      • exclude (optional): An array of strings used to filter out results based on their associated GitHub topics. If configured, all repositories except those with one (or more) topics(s) present in the exclusion filter will be ingested.
    • visibility (optional): An array of strings used to filter results based on their visibility. Available options are private, internal, public. If configured (non empty), only repositories with visibility present in the filter will be ingested
    • allowArchived (optional): Whether to include archived repositories. Defaults to false.
  • host (optional): The hostname of your GitHub Enterprise instance. It must match a host defined in integrations.github.
  • organization: Name of your organization account/workspace. If you want to add multiple organizations, you need to add one provider config each.
  • validateLocationsExist (optional): Whether to validate locations that exist before emitting them. This option avoids generating locations for catalog info files that do not exist in the source repository. Defaults to false. Due to limitations in the GitHub API's ability to query for repository objects, this option cannot be used in conjunction with wildcards in the catalogPath.
  • schedule:
    • frequency: How often you want the task to run. The system does its best to avoid overlapping invocations.
    • timeout: The maximum amount of time that a single task invocation can take.
    • initialDelay (optional): The amount of time that should pass before the first invocation happens.
    • scope (optional): 'global' or 'local'. Sets the scope of concurrency control.

GitHub API Rate Limits​

GitHub rate limits API requests to 5,000 per hour (or more for Enterprise accounts). The snippet below refreshes the Backstage catalog data every 35 minutes, which issues an API request for each discovered location.

If your requests are too frequent then you may get throttled by rate limiting. You can change the refresh frequency of the catalog in your app-config.yaml file by controlling the schedule.

schedule:
  frequency: { minutes: 35 }
  timeout: { minutes: 3 }

More information about scheduling can be found on the SchedulerServiceTaskScheduleDefinition page.

Alternatively, or additionally, you can configure github-apps authentication which carries a much higher rate limit at GitHub.

This is true for any method of adding GitHub entities to the catalog, but especially easy to hit with automatic discovery.