Function Compute:Lifecycle hooks for function instances

Background information

When you implement and configure an instance lifecycle hook, Function Compute calls the corresponding hook when a lifecycle event occurs. The PHP runtime supports Initializer and PreStop instance lifecycle hooks. For more information, see Configure instance lifecycles.

Billing for instance lifecycle hooks is the same as for regular function invocations. However, their execution logs appear only in Real-time Logs, Function Logs, or Advanced Logs. The Invocation Request List does not display logs for hooks. For more information, see View instance lifecycle hook logs.

Initializer hook

Initializer Example

An Initializer hook runs after a function instance starts and before the handler runs. Function Compute ensures that an Initializer hook runs successfully only once during the lifecycle of an instance. If the Initializer hook fails to run, the function invocation fails. On the next invocation, Function Compute creates a new instance to run the initializer hook.

The Initializer hook has only one input parameter, $context, which is used in the same way as a handler.

The following code shows a simple Initializer hook example.

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

my_initializer is the name of the Initializer callback method, which must match the Initializer Hook that you configure in the Function Compute console. For example, if you set the Initializer Hook for your function to main.my_initializer, Function Compute loads the my_initializer method that is defined in main.php after the Initializer property is configured.

Method Signature

• The only input parameter is context. The information in this parameter is the same as that in the context parameter for a handler.

• The context fields initializer and initializationTimeout are designed for the Initializer hook. If you use an Initializer hook, these fields are set to the values of the Initializer Hook and Initializer Hook Timeout that you configure for your function. Otherwise, the fields are empty and the hook does not take effect.

• No value is returned.

PreStop hook

A PreStop hook runs before a function instance is destroyed. Its method signature is the same as that 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

Configure Using The Console

edition: 3.0.0
name: fcDeployApp
access: "default"

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

resources:
  hello_world:
    component: fc3 # Component name
    props:
      region: ${vars.region}              # For more information about how to use variables, see 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:      # Extension function
        initializer:                # Initializer hook
          handler: index.my_initializer 
          timeout: 60     
        preStop:                    # PreStop hook
          handler: index.preStop    # Handler
          timeout: 60               # 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, the Initializer hook retrieves the MySQL database configuration from environment variables, creates a connection to the MySQL database, and then tests the connectivity. The PreStop hook closes the MySQL connection. For more information, see php72-mysql.