Function Compute:Instance lifecycle hooks

Invoke code

After you configure an `invoke code` hook, the system sends an HTTP request to your function. A `POST /initialize` request is sent when the instance starts, and a `GET /pre-stop` request is sent when the instance stops. You must handle these requests in your business code.

To use an Initializer hook in a custom image, you must implement the logic for the `POST /initialize` path in your HTTP server. Similarly, for PreStop hooks, you must implement the logic for the `GET /pre-stop` path. The following example uses a custom runtime for Python 3.10.

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)

In addition to the preceding code, a function execution error can occur in Python. The following code shows an example of an error scenario for /initialize.

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

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

Execute instruction

You can configure a callback instruction to perform initialization operations after the function instance starts. You can use any shell implementation that is supported by the function runtime environment, such as /bin/bash, /bin/sh, /bin/csh, or /bin/zsh.

The Function Compute console provides two preset shells: /bin/bash and /bin/sh. The following example uses /bin/sh.

#!/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 the exit code of the callback instruction is 0, the execution is successful. Any other exit code indicates a failure. You can output error messages to standard error (stderr) in the script to help diagnose errors. For example, the following code snippet shows how to output error information and set the exit code to 1 after a curl request fails.

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

Invoke code

Execute instruction

If the exit code of the instruction is not 0, the instruction is not re-executed, and the system returns an error.