6. Push Notifications and Spring Cloud Bus

Many source code repository providers (like Github, Gitlab or Bitbucket for instance) will notify you of changes in a repository through a webhook. You can configure the webhook via the provider’s user interface as a URL and a set of events in which you are interested. For instance Github will POST to the webhook with a JSON body containing a list of commits, and a header "X-Github-Event" equal to "push". If you add a dependency on the spring-cloud-config-monitor library and activate the Spring Cloud Bus in your Config Server, then a "/monitor" endpoint is enabled.

When the webhook is activated the Config Server will send a RefreshRemoteApplicationEvent targeted at the applications it thinks might have changed. The change detection can be strategized, but by default it just looks for changes in files that match the application name (e.g. "foo.properties" is targeted at the "foo" application, and "application.properties" is targeted at all applications). The strategy if you want to override the behaviour is PropertyPathNotificationExtractor which accepts the request headers and body as parameters and returns a list of file paths that changed.

The default configuration works out of the box with Github, Gitlab or Bitbucket. In addition to the JSON notifications from Github, Gitlab or Bitbucket you can trigger a change notification by POSTing to "/monitor" with a form-encoded body parameters path={name}. This will broadcast to applications matching the "{name}" pattern (can contain wildcards).

	Note
	the RefreshRemoteApplicationEvent will only be transmitted if the spring-cloud-bus is activated in the Config Server and in the client application.

	Note
	the default configuration also detects filesystem changes in local git repositories (the webhook is not used in that case but as soon as you edit a config file a refresh will be broadcast).