{:title "Build triggers" :category :builds :index 40}

In order for a build to run, it must first be triggered. MonkeyCI has several ways to do this:

1. Start it manually via the UI.
2. Start it via the API.
3. Start it via a public trigger endpoint.

Manual Triggers

Now, steps 1 and 2 are basically the same, since the UI eventually calls the API, with the token that is created when the user authenticates. If you have such a token, you could also trigger a build using tools like cURL. If you would like to trigger a build manually, you can navigate to the repository screen and then press the Trigger Build button. A form is then displayed where you can specify which branch or tag to run the build from. On confirmation, a new build is started.

External Triggers

But the most often used way to start a build is automatically, on a push to a git repository. MonkeyCI supports several platforms that can do this. See the platforms page for more details on this. But for these triggers to work, you need to tell it where to send the trigger to. That's where webhooks come in. These are essentially HTTP endpoints that accept a POST request with details about the push event. MonkeyCI will then use that information to start a new build.

Security

Of course, we don't just allow anybody to trigger events as they please. There is a security check to see whether the caller is actually permitted to trigger builds. MonkeyCI supports HMAC checks on webhook invocations. For this, a secret key is required to calculate an HMAC signature, that is passed along as a request header. MonkeyCI then verifies if the signature matches the content of the request.

When you create a new webhook, a URL along with the secret is generated and stored in the database. Store this secret in a secure place, because it's not possible to retrieve it afterwards. If it's lost, you will need to recreate the webhook. The API returns this secret on creation, and it's displayed once in the user interface.

Depending on the platform you generated the webhook for, the url is different. You will need both the url and the secret to configure the webhook in the platform that will invoke the webhook. The contents should be put in the request body as JSON.

When the webhook is correctly configured in the client platform, MonkeyCI will start a new build whenever it receives a correctly formatted (and secured) request.