GitHub Slack Bridge

This service forwards GitHub webhook events to Slack channels.

Single-repository setup

1. Go to your GitHub repository and click on Settings.
2. Select Webhooks from the left sidebar.
3. Click the Add webhook button.
4. In the Payload URL field, enter: https://your-deployment-url/webhook/your-slack-channel
   • Replace your-deployment-url with the base URL where this service is deployed (for EnTur, this is github-slack-bridge.dev.entur.org).
   • Replace your-slack-channel with the name of the Slack channel you want to send notifications to.
5. Set the Content type to application/json.
6. In the Secret field, enter your webhook secret. This field is mandatory and must match the GITHUB_WEBHOOK_SECRET environment variable set in the service (for EnTur, this is available in 1Password).
7. Under Which events would you like to trigger this webhook?:
   • Select Let me select individual events.
   • Check the following events: Push, Pull requests, and Workflow runs.
8. Make sure Active is checked.
9. Click Add webhook to save your configuration.

After setting up the webhook, GitHub will send a ping event to verify the connection. You should see this event in your service logs.

Batch setup

If you want to add the webhook to multiple repositories, you can use the gh_webook_tool.sh script to automate the process. For EnTur, the secret is available in 1Password. By default it does not make any changes. Add --no-dry-run to actually make changes:

./batch_add_webhook.sh --secret 'webhook secret' --channel 'your-slack-channel' topic some-topic # For RoR we use 'ror'
./batch_add_webhook.sh --secret 'webhook secret' --channel 'your-slack-channel' team some-team # For RoR we use 'team-ruter-reiseplanlegger'

Development

Server API Endpoint

POST /webhook/{channel}

Configure your GitHub repository webhooks to send events to this endpoint. The {channel} parameter in the URL specifies which Slack channel should receive the notifications.

Service Configuration

This service requires the following environment variables (for EnTur, these are available in 1Password):

• SLACK_WEBHOOK_URL - Required. The Slack incoming webhook URL that messages will be sent to.
  • Example: https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXX
• GITHUB_WEBHOOK_SECRET - Required. The secret used to validate GitHub webhook payloads.

Supported GitHub Events

• Push events (to main/master/prod branches)
• Pull request events (opened, closed, reopened)
• Workflow run events (failed builds and fixed builds)

Requirements

• Java 21 or higher
• Kotlin 2.2.0

Running the Application

Using Gradle

./gradlew run

Using Docker

docker build -t github-slack-bridge .
docker run -p 8080:8080 \
  -e SLACK_WEBHOOK_URL=your_slack_webhook_url \
  -e GITHUB_WEBHOOK_SECRET=your_github_secret \
  github-slack-bridge

Using the JAR

./gradlew shadowJar
java -jar build/libs/github-slack-bridge-all.jar

Running Tests

./gradlew test

Building

./gradlew build

License

This project is maintained by EnTur, using European Union Public License 1.2