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GitHub Discovery

The GitHub integration has a special discovery processor for discovering catalog entities within a GitHub organization. The processor 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.

Installation

You will have to add the processors in the catalog initialization code of your backend. They are not installed by default, therefore you have to add a dependency on @backstage/plugin-catalog-backend-module-github to your backend package, plus @backstage/integration for the basic credentials management:

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

And then add the processors to your catalog builder:

// In packages/backend/src/plugins/catalog.ts
+import {
+  GithubDiscoveryProcessor,
+  GithubOrgReaderProcessor,
+} from '@backstage/plugin-catalog-backend-module-github';
+import {
+  ScmIntegrations,
+  DefaultGithubCredentialsProvider
+} from '@backstage/integration';

 export default async function createPlugin(
   env: PluginEnvironment,
 ): Promise<Router> {
   const builder = await CatalogBuilder.create(env);
+  const integrations = ScmIntegrations.fromConfig(env.config);
+  const githubCredentialsProvider =
+    DefaultGithubCredentialsProvider.fromIntegrations(integrations);
+  builder.addProcessor(
+    GithubDiscoveryProcessor.fromConfig(env.config, {
+      logger: env.logger,
+      githubCredentialsProvider,
+    }),
+    GithubOrgReaderProcessor.fromConfig(env.config, {
+      logger: env.logger,
+      githubCredentialsProvider,
+    }),
+  );

Configuration

To use the discovery processor, you'll need a GitHub integration set up with either a Personal Access Token or GitHub Apps.

Then you can add a location target to the catalog configuration:

catalog:
  locations:
    # (since 0.13.5) Scan all repositories for a catalog-info.yaml in the root of the default branch
    - type: github-discovery
      target: https://github.com/myorg
    # Or use a custom pattern for a subset of all repositories with default repository
    - type: github-discovery
      target: https://github.com/myorg/service-*/blob/-/catalog-info.yaml
    # Or use a custom file format and location
    - type: github-discovery
      target: https://github.com/*/blob/-/docs/your-own-format.yaml
    # Or use a specific branch-name
    - type: github-discovery
      target: https://github.com/*/blob/backstage-docs/catalog-info.yaml

Note the github-discovery type, as this is not a regular url processor.

When using a custom pattern, the target is composed of three parts:

• The base organization URL, https://github.com/myorg in this case
• The repository blob to scan, which accepts * wildcard tokens. This can simply be * to scan all repositories in the organization. This example only looks for repositories prefixed with service-.
• The path within each repository to find the catalog YAML file. This will usually be /blob/main/catalog-info.yaml, /blob/master/catalog-info.yaml or a similar variation for catalog files stored in the root directory of each repository. You could also use a dash (-) for referring to the default branch.

GitHub API Rate Limits

GitHub rate limits API requests to 5,000 per hour (or more for Enterprise accounts). The default Backstage catalog backend refreshes data every 100 seconds, which issues an API request for each discovered location.

This means if you have more than ~140 catalog entities, you may get throttled by rate limiting. You can change the refresh rate of the catalog in your packages/backend/src/plugins/catalog.ts file:

const builder = await CatalogBuilder.create(env);

// For example, to refresh every 5 minutes (300 seconds).
builder.setProcessingIntervalSeconds(300);

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.