Instance lifecycle hooks

Background

A function instance's lifecycle includes Initializer and PreStop hooks. The Initializer hook has two types: invoke code and execute instruction. Currently, only GPU-accelerated functions support the execute instruction type of Initializer hook. For more information, see Configure instance lifecycle.

Instance lifecycle hooks follow the same billing rules as regular invocation requests. However, you can view their execution logs only in Real-time Log, Function Logs, or Advanced Logs. The Invocation Request List does not show hook logs. For more information, see View instance lifecycle hook logs.

Implementing hook methods

A function instance's lifecycle in Function Compute includes Initializer and PreStop hooks. You can configure an Initializer hook as either invoke code or execute instruction, but not both.

import os
from flask import Flask
from flask import request
app = Flask(__name__)
@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"
@app.route('/', defaults={'path': ''})
@app.route('/<path:path>', methods=['GET', 'POST', 'PUT', 'DELETE'])
def hello_world(path):
    rid = request.headers.get('x-fc-request-id')
    print("FC invoke Start RequestId: " + rid)
    # do your things
    print("FC invoke End RequestId: " + rid)
    return "Hello, World!", 200, [('Function-Name', os.getenv('FC_FUNCTION_NAME'))]
@app.route('/pre-stop', methods=['GET'])
def prestop_invoke():
    rid = request.headers.get('x-fc-request-id')
    print("FC PreStop Start RequestId: " + rid)
    # do your things
    print("FC PreStop End RequestId: " + rid)
    return "OK"
if __name__ == '__main__':
    app.run(host='0.0.0.0', port=9000)

@app.route('/initialize', methods=['POST'])
def init():
    raise Exception("hahaha")
    return "OK", 200, []

@app.route('/initialize', methods=['POST'])
def init():
    return "OK", 404, []

#!/bin/sh
URL="http://localhost:7860"
REQUEST_PATH="sdapi/v1/txt2img"
JSON_DATA='{
	"prompt": "",
	"steps": 1,
	"height": 8,
	"width": 8
}'
temp_file=$(mktemp)
trap 'rm -f "$temp_file"' EXIT
if ! http_code=$(curl -s -w "%{http_code}" \
	-H "Content-Type: application/json" \
	-d "$JSON_DATA" \
	-o "$temp_file" \
	-X POST "$URL"/"$REQUEST_PATH"); then
	echo "{\"status\": \"curl_error\", \"code\": $curl_exit_code}" \
	| jq . >&2
	exit 1
fi
response=$(<"$temp_file")
echo "http code $http_code"
if [ "$http_code" -eq 200 ]; then
	echo "$response" | jq -r '.' || printf "%s\n" "$response"
	exit 0
else
	echo "$response_body" \
	| jq -c 'if type == "object" then . else {raw: .} end' 2>/dev/null \
	| jq -s '{status: "http_error", code: $code, response: .[0]}' \
		--arg code "$http_code" \
		>&2
	exit 1
fi

if ! http_code=$(curl -s -w "%{http_code}" \
	-H "Content-Type: application/json" \
	-d "$JSON_DATA" \
	-o "$temp_file" \
	-X POST "$URL"/"$REQUEST_PATH"); then
	echo "{\"status\": \"curl_error\", \"code\": $curl_exit_code}" \
	| jq . >&2
	exit 1
fi

Hook error codes

Configure lifecycle hooks

1. Log on to the Function Compute console. In the left-side navigation pane, click Functions.

2. In the top navigation bar, select a region. On the Functions page, click the function that you want to manage.

3. On the function details page, click the Configuration tab. In the Instance Configuration section, click Modify.

4. In the Instance Configuration panel, configure the Initializer hook and set the Initializer timeout.

   • invoke code

     Turn on the Initializer hook switch. Set the Initializer timeout to 300 seconds. For hook type, select invoke code or execute instruction. After the hook is enabled, Function Compute sends an HTTP POST /initialize request when an instance starts. Your code must handle this request and return a 200 status code. If a 4xx or 5xx status code is returned, Function Compute returns an error or restarts the instance.

   • execute instruction

     The console provides two preset shell implementations: /bin/bash and /bin/sh.

     Turn on the Initializer hook switch, set the Initializer timeout to 300 seconds, and select execute instruction as the hook type. For the command, select /bin/sh. In the code editor, write a health check script. For example, use curl to send a POST request to localhost:7860/sdapi/v1/txt2img with JSON parameters including prompt, steps, height, and width. Use mktemp to create a temporary file and trap to set up cleanup.

5. In the Instance Configuration panel, configure the PreStop hook and its timeout, and then click Deploy.

   Turn on the PreStop hook switch and set the PreStop timeout to 3 seconds.

View instance lifecycle hook logs

You can view hook logs by using the Function Logs feature.

1. Log on to the Function Compute console. In the left-side navigation pane, click Functions.

2. In the top navigation bar, select a region. On the Functions page, click the function that you want to manage.

3. On the function details page, click the Test tab, click Test Function, and then choose Logs > Function Logs.

   On the Function Logs tab, you can view the function's invocation logs and Initializer hook logs. The following is an example:

   2024-06-26 10:59:23FC Initialize Start RequestId: 529eab23-9b3a-4ffc-88c8-9a686*******
   2024-06-26 10:59:23FC Initialize End RequestId: 529eab23-9b3a-4ffc-88c8-9a686*******
   2024-06-26 10:59:25FC Invoke Start RequestId: 1-667b840c-15c49df0-b7dc1*******
   2024-06-26 10:59:25FC Invoke End RequestId: 1-667b840c-15c49df0-b7dc1*******

   Since function instances are cached and not immediately destroyed, PreStop hook logs are not available instantly. To quickly trigger the PreStop hook, you can update the function's configuration or code. After the update is complete, check Function Logs again to view the PreStop hook logs. The following is an example:

   2024-06-26 11:04:33FC PreStop Start RequestId: c4385899-f071-490e-a8b7-e33c5*******
   2024-06-26 11:04:33FC PreStop End RequestId: c4385899-f071-490e-a8b7-e33c5*******