Lifecycle hooks for function instances - Function Compute

This topic describes how to implement lifecycle hooks for function instances in a Custom Container runtime.

Lifecycle hooks

After you configure and implement a lifecycle hook for your function instances, Function Compute invokes the hook when the corresponding lifecycle event occurs. The following lifecycle hooks can be configured for a function instance: Initializer, PreFreeze, and PreStop. For more information, see Function instance lifecycle.

The following table describes the Initializer hook. The PreFreeze and PreStop hooks function similarly.

Path	Input request	Expected response
(Optional) POST `/initialize`	Request body: none. Request header: common request headers. For more information, see Common request headers in Function Compute.	Response body: the return value of `Initializer`. StatusCode 200: succeeded. 404: failed. Sample code of `initialize` in Python: `@app.route('/initialize', methods=['POST']) def init_invoke(): rid = request.headers.get(x-fc-request-id) print("FC Initialize Start RequestId: " + rid) # do your things print("FC Initialize End RequestId: " + rid) return "OK"`
(Optional) GET `/pre-freeze`	Request body: none. Request header: common request headers. For more information, see Common request headers in Function Compute.	Response body: the return value of PreFreeze. StatusCode 200: succeeded. 404: failed.
(Optional) GET `/pre-stop`	Request body: none. Request header: common request headers. For more information, see Common request headers in Function Compute.	Response body: the return value of PreStop. StatusCode 200: succeeded. 404: failed.

If you want to use the Initializer hook in a custom runtime, you must implement the corresponding logic with the /initialize path and the POST method in your HTTP server. You can refer to the sample code of initialize in the preceding table.

Important

If you do not configure an Initializer hook when you create a function, you do not need to implement /initialize. In this case, even if your HTTP server implements /initialize, the /initialize logic in your code cannot be called and executed.