Function Compute:Configure instance lifecycles

Function instance lifecycle

Instances are dynamically created and destroyed based on incoming requests. The lifecycle of each instance comprises three phases: Creating, Invoke, and Destroy. The following figure shows the lifecycle of a function instance.

Creating

Function Compute creates instances based on your function configurations. During this phase, Function Compute performs the following tasks in sequence:

1. Instance Create: Function Compute loads code and layers, or pulls images, and then initializes an instance.

2. Runtime Init: Function Compute initializes the runtime.

3. Init Hook: Function Compute executes the configured Initializer hook. For more information, see Initializer hooks.

The following figure shows the Creating phase.

Invoke

Handlers act as entry points for your function instances to process internal and external requests. An instance that runs in a built-in runtime of Function Compute processes one request at a time, whereas an instance that runs in a custom runtime or Custom Container runtime can process concurrent requests. To allow an instance to process multiple requests at a time, you can set the Instance Concurrency parameter to a value greater than 1 when you create a function. For more information, see Create a web function.

You are charged only when your instances process requests and execute hooks. Instances that are not actively in use are frozen and thus do not generate any costs. For more information, see Billing.Function Compute

Destroy

If a function instance does not receive any invocations for a certain period of time, the Destroy phase is triggered. During this phase, Function Compute executes the PreStop hook first, which is typically used to perform cleanup activities.

Instances are destroyed in the following scenarios:

• Idle instances: If an instance does not receive any invocations for a certain period of time, Function Compute automatically reclaims the instance.

• Provisioned instance adjustment: When you decrease the number of provisioned instances, Function Compute immediately destroys any excess instances.

• Instance exceptions: If an instance encounters an exception in the Creating or Invoke phase, Function Compute destroys the instance.

Instance freezing mechanism

Function Compute freezes instances that are not invoked by any requests, and unfreezes, or thaws, them when they receive requests.Function Compute The following figure shows the freezing mechanism.

The freezing mechanism is triggered in the following scenarios:

• The instance is initialized but not yet invoked by any requests.

• The instance completes processing its last request and is not receiving any new ones.

Function Compute freezes an instance after the Invoke phase. During the freeze period, all background processes, threads, and coroutines in the program cease to run, and asynchronous logs may fail to write.

Limits

• All runtimes support the Initializer and PreStop hooks.

• The input parameters of a PreStop hook do not contain an event parameter.

• The PreStop hook does not support returning values, and any logic added to the hook to return values is ineffective.

• If you use a Java runtime, you must update fc-java-core to 1.4.0 or later to utilize the PreStop hook functionality.

• When a function returns responses, Function Compute freezes the function instance. At this point, you cannot assume that all asynchronous processes, threads, and coroutines are successfully executed, nor can you expect the asynchronous logs to be updated.

Billing

You are not charged for the number of times the lifecycle hooks are executed. All billable items involved during lifecycle hook invocations are billed in the same manner as regular invocations. The following figure shows the billing durations. For more information about billing, see Billing overview.

Prerequisite

Function creation is completed. For more information, see Create a function.

Configure lifecycle hooks

  codeUri: './code.zip'
  ......
  instanceLifecycleConfig:
    preStop:
      handler: index.PreStop
      timeout: 60

  codeUri: './code.zip'
  ......
  instanceLifecycleConfig:
    preStop:
      handler: ""
      timeout: 60

Query hook-related logs

After you configure an instance lifecycle hook and run its code, you can query the logs related to the hook.

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

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

1. On the Function Details page of your function, click the Logs tab. On the Invocation Requests tab, find the request whose logs you want to view and click Advanced Logs in the Actions column.

   You can use a copied instance ID to query the start and end logs of all lifecycle hooks. You can also use the instance ID together with a hook keyword to query the start and end logs of a specified hook, such as c-62833f38-20f1629801fa4bd***** and PreStop.

   You can also query the request logs based on the request ID in the start and end logs. If the user log does not contain a request ID, you can click the icon to obtain the context log.