Function Compute:Lifecycle hooks for function instances

Background

After you configure a lifecycle hook for a function instance, Function Compute invokes the hook when the corresponding instance lifecycle event occurs. In a PHP runtime, you can configure Initializer and PreStop hooks for function instances. For more information, see Function instance lifecycles.

The billing rules for lifecycle hooks of function instances are the same as the billing rules for common invocation requests. However, the execution logs can be queried only in Function Logs, Instance Logs, and Advanced Logs. Logs for lifecycle hooks are not displayed in the invocation request list. For more information, see Query logs related to hooks.

Initializer hooks

Example

An Initializer hook is invoked after a function instance is started and before a handler is run. Function Compute ensures that the Initializer hook is successfully invoked only once in the lifecycle of a function instance. If the Initializer hook fails to be invoked, the system retries the Initializer hook until the Initializer hook is successfully invoked, and then runs your handler. To make sure that the Initializer hook can be repeatedly retried, configure the Initializer hook properly.

An Initializer hook contains only the $context parameter and can be used in the same way as a handler.

The following sample code provides an example of a simple Initializer hook:

<?php
function my_initializer($context) {
    $logger = $GLOBALS['fcLogger'];
    $logger->info("hello world");
}
?>            

In the preceding sample code, my_initializer is the method name of the Initializer hook. The method name must be the same as that in the value of the Initializer Hook parameter that is configured for your function in the Function Compute console. For example, if the value of the Initializer Hook parameter is main.my_initializer, Function Compute loads the my_initializer method that is defined in the main.php file after the Initializer property is configured.

Method signature

• The Initializer hook contains only the context parameter. The information specified by this parameter is the same as the value of the context parameter specified for a handler.

• The initializer and initializationTimeout parameters in context are used for the Initializer hook. If you want to use an Initializer hook, set the two parameters to the values of the Initializer Hook and Initializer Hook Timeout Period parameters that you configure for your function. Otherwise, the values are empty and the hook does not take effect.

• No value is returned.

PreStop hooks

A PreStop hook is executed before a function instance is destroyed. The method signature of a PreStop hook is the same as the method signature of an Initializer hook.

<?php

$counter = 0;
function preStop($context) {
    $GLOBALS['fcLogger']->info("preStop ok");
}

function handler($event, $context) {
    global $counter;
    $counter += 2;
    return $counter;
}
?>

<funcName> AND <ServiceName> AND qualifier: <VERSION>

Configure lifecycle hooks

Use the Function Compute console

edition: 3.0.0
name: fcDeployApp
access: "default"

vars: # Global variables
  region: "cn-hangzhou"

resources:
  hello_world:
    component: fc3 # The component name
    props:
      region: ${vars.region}              # For information about how to use variables, visit: https://docs.serverless-devs.com/serverless-devs/yaml#%E5%8F%98%E9%87%8F%E8%B5%8B%E5%80%BC.
      functionName: "testphp"
      description: 'this is a test'
      runtime: "php7.2"
      code: ./
      handler: index.handler
      memorySize: 128
      timeout: 30
      instanceLifecycleConfig:      # The extension function
        initializer: # The Initializer hook
          handler: index.my_initializer 
          timeout: 60     
        preStop:                                     # The PreStop hook
          handler: index.preStop    # The handler
          timeout: 60               # The timeout period
 

View the logs of instance lifecycle hooks

You can view the logs for lifecycle hook in Logs.

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 Function tab, click Test Function, and then choose Logs > Function Logs.

   On the Logs tab, you can view function invocation logs and Initializer logs. Example:

   2024-03-04 17:57:28FC Initialize Start RequestId: 1-65e59b07-1520da26-bf73bbb91b69
   2024-03-04 17:57:282024-03-04 09:57:28.192 1-65e59b07-1520da26-bf73bbb91b69 [info] initializer
   2024-03-04 17:57:28FC Initialize End RequestId: 1-65e59b07-1520da26-bf73bbb91b69
   2024-03-04 17:57:28FC Invoke Start RequestId: 1-65e59b07-1520da26-bf73bbb91b69
   2024-03-04 17:57:28FC Invoke End RequestId: 1-65e59b07-1520da26-bf73bbb91b69

   Each function instance is cached for a period of time and not immediately destroyed, you cannot view logs for PreStop hooks right away. To quickly trigger a PreStop hook, you can update the function configurations or function code. After the update is complete, you can view the logs for PreStop hooks in Function Logs. The following sample code shows an example:

   2024-03-04 18:33:26FC PreStop Start RequestId: 93c93603-9fbe-4576-9458-193c8b213031
   2024-03-04 18:33:262024-03-04 10:33:26.077 93c93603-9fbe-4576-9458-193c8b213031 [info] preStop
   2024-03-04 18:33:26FC PreStop End RequestId: 93c93603-9fbe-4576-9458-193c8b213031

Sample program

Function Compute provides a sample MySQL program that uses Initializer and PreStop hooks. In this example, an Initializer hook is used to obtain MySQL database configurations from environment variables, create MySQL database connections, and test connectivity. A PreStop hook is used to close MySQL connections. For more information, see php72-mysql.