Concourse webhook broadcaster

This repo contains a small service that is meant to be run as a sidecar to a concourse deployment.

Its purpose is to process incoming webhooks from a github repository and broadcast them to all concourse resources that reference the git repository.

  ┌─────────────┐
┌─┤  Concourse  ├────────────────┐                                           ┌─────────────────────┐
│ └─────────────┘                │                                         ┌─┤ Github (Enterprise) ├─┐
│ ┌────────────────────────────┐ │                                         │ └─────────────────────┘ │
│ │name: resource1             │ │                                         │                         │
│ │type: git                   │ │                                         │                         │
│ │source:                     │◀┼─┐                                       │                         │
│ │  uri: github.com/some/where│ │ │                                       │                         │
│ └────────────────────────────┘ │ │                                       │                         │
│ ┌────────────────────────────┐ │ │    ┌─────────────────────┐            │                         │
│ │name: resource2             │ │ │    │                     │            │ ┌─────────────────────┐ │
│ │type: git                   │ │ │    │                     │    push    │ │     repository:     │ │
│ │source:                     │◀┼─┼────│ Webhook Broadcaster │◀───────────┼─│     some/where      │ │
│ │  uri: github.com/some/where│ │ │    │                     │   webhook  │ └─────────────────────┘ │
│ └────────────────────────────┘ │ │    │                     │            │                         │
│ ┌────────────────────────────┐ │ │    └─────────────────────┘            │                         │
│ │name: resource3             │ │ │                                       │                         │
│ │type: git                   │ │ │                                       │                         │
│ │source:                     │◀┼─┘                                       │                         │
│ │  uri: github.com/some/where│ │                                         │                         │
│ └────────────────────────────┘ │                                         │                         │
└────────────────────────────────┘                                         └─────────────────────────┘

Why?

Our concourse deployment was causing considerable load on our github enterprise appliance and we needed to increase the check_every properties on all our git resources and rely on resource webhooks to propagte updates in a timely fashion.

We are also using a single repository in 300 resources across 70 pipelines and adding 300 webhooks to this github repository is unfeasable.

How?

The webhook broadcaster periodically (--refresh-interval) fetches all pipelines via the concourse api and builds up a cache of all resources that have a webhook_token configured. When a push event is received the broadcaster scans its local cache and calls the webhook url of all resources that reference this particular repository using the resources individual webhook_token.

Usage

1. Start a webhook-broadcaster you need to provide the following configuration
   • --concourse-url external url of your concourse deployment
   • --auth-user concourse basic auth admin user.
   • --auth-password concourse basic auth admin password
2. Create a github webhook for push events pointing it to http://webhook-broadcaster.somewhere:8080/github
3. Make sure resources of type git have a webhook_token configured

Compatibility

• webhook-broadcaster should work with concourse >=4.x. There is a branch https://github.com/sapcc/webhook-broadcaster/tree/concourse-3.x that supports concourse 3.x.
• The broadcaster only supports github webhooks yet. Adding different types of webhooks, even for resources of different types should be simple (PRs welcome).