Function Compute:Create a web function

Create a function

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 Create Function.

3. On the Create Function page, select Web Function, configure the following parameters, and then click Create.

   • Basic Settings: Configure Function Name.

   • Code: Configure the runtime and code-related information of the function.

     Parameter	Description	Example
     Runtime	Select a runtime that you prefer, such as a Python, Java, PHP, Node.js, or Custom Container Image.	Node.js 16
     Code Upload Method	Specify how you want code to be uploaded to Function Compute. Use Sample Code: You can select the sample code provided by Function Compute to create a function based on your business requirements. This is the default method. Upload ZIP: Select and upload a .zip file that contains your function code. Upload Folder: Select and upload the folder that contains your function code. OSS: Upload code from an Object Storage Service (OSS) bucket. In this case, you must specify the Bucket Name and Object Name parameters. Use Sample Images: Select a sample image that comes with Function Compute. Use Container Registry Images: Select an image from Container Registry. In the Select Container Image panel, specify the Container Image Instance and Container Registry Repository parameters, find the desired image, and click Select in the Actions column.	Use Sample Code
     Startup Command	Configure the startup command of the program. If you do not configure the startup command, you must manually create a startup script named bootstrap in the root directory of the code. The bootstrap script is used to start your program.	npm run start
     Listening Port	Specify the port on which the HTTP server in your code listens.	9000

   • In the Advanced Settings section, configure instance settings and other items such as the function execution timeout period. The following table describes the parameters.

   • Parameter	Description	Example
     Specifications	Configure instance specifications, such as vCPU Capacity and Memory Capacity based on your business requirements. For more information about the billing of resources, see Billing overview. Note The ratio of vCPU capacity to memory capacity (in GB) must be set within a range of 1:1 to 1:4.	0.35 vCPUs, 512 MB
     Size of Temporary Disk	Specify the size of the disk used to temporarily store files based on your business requirements. Valid values: 512 MB: the default value. You are not charged for using a temporary disk of this size. Function Compute provides you with a free disk space of 512 MB. 10 GB: You are charged based on the disk size of 9.5 GB. Note Data shares the space of the temporary disk and can be written to all directories in the disk. The size of the temporary disk changes with the lifecycles of underlying instances. After an instance is recycled by the system, the corresponding data on the disk is cleared. To persist files, you can use Apsara File Storage NAS (NAS) or OSS. For more information, see Configure a NAS file system and Configure an OSS file system.	512 MB
     Execution Timeout Period	Specify the timeout period of a function execution. The default timeout period is 60 seconds, and the maximum value is 86,400 seconds. Note If the execution of the function times out, the function fails to be executed. If you require a longer timeout limit, join the DingTalk group 11721331 for technical support.	60
     Instance Concurrency	Note This parameter is required if you select Web Function or Container Images to create a function. Function Compute supports the instance concurrency feature, which allows an instance to process multiple requests at the same time. The Instance Concurrency parameter specifies the maximum number of requests a function instance can process at the same time. For more information, see Configure instance concurrency.	20
     Time Zone	Specify the time zone of the function. After you configure the time zone of the function, the environment variable TZ is automatically added to the function. The value is the time zone that you configure.	UTC
     Function Role	Specify the RAM role of the function. Function Compute uses this role to generate a temporary AccessKey pair for accessing your Alibaba Cloud resources and passes the AccessKey pair to your code. For more information, see Grant Function Compute permissions to access other Alibaba Cloud services.	mytestrole
     Access to VPC	Specify whether to allow the function to access virtual private cloud (VPC) resources. For more information, see Configure network settings.	Yes
     VPC	Specify the VPC. This parameter is required if you set Access to VPC to Yes. Create a VPC or select the ID of an existing VPC that you want to access from the drop-down list.	fc.auto.create.vpc.1632317****
     vSwitch	Specify the vSwitch. This parameter is required if you set Access to VPC to Yes. Create a vSwitch or select the ID of an existing vSwitch from the drop-down list.	fc.auto.create.vswitch.vpc-bp1p8248****
     Security Group	Specify the security group. This parameter is required if you set Access to VPC to Yes. Create a security group or select an existing security group from the drop-down list.	fc.auto.create.SecurityGroup.vsw-bp15ftbbbbd****
     Allow Default NIC to Access Internet	Specify whether to allow the function to access the Internet through the default network interface controller (NIC). If you select No, the function cannot access the Internet through the default NIC of Function Compute. Important If you use a static public IP address, you must set Allow Default NIC to Access Internet to No. Otherwise, the configured static public IP address does not take effect. For more information, see Configure static public IP addresses.	Yes
     Logging	Specify whether to enable the logging feature. Valid values: Enable: Function execution logs are persistently stored in Simple Log Service for code debugging, fault analysis, and data analysis. Disable: You cannot use Simple Log Service to store or query function execution logs.	Enable

   • In the Environment Variables section, configure environment variables for the runtime of the function. For more information, see Configure environment variables.

4. After the function is created, go to the Function Details page. On the Code tab, you can modify, deploy, and test the function.

Configure instance concurrency

Instance concurrency specifies the maximum number of concurrent requests that each function instance can process at the same time. You can use the instance concurrency feature of Function Compute to manage resource usage in an efficient manner during traffic peaks and mitigate the impact of cold starts. This helps improve performance and reduce costs.

Background

Function Compute is billed based on the execution duration of instances. For example, 3 requests need to be processed at the same time. The processing of each request lasts 10 seconds. The following items describe the execution duration for different concurrency values:

The following figure shows the difference in request execution when instance concurrency is set to different values.

Impacts

This section compares the instance concurrency of a value of 1 (instance concurrency = 1) and the instance concurrency of a value greater than 1 (instance concurrency > 1).

Billing

The execution duration is different for different instance concurrency values. As a result, costs are different. For more information, see Billing overview.

Instance concurrency = 1

An instance can process only one request at the same time. The billing duration starts when the first request starts to be processed and ends when the last request is processed.

Instance concurrency > 1

Each instance can concurrently process multiple requests. The actual running duration of instances is used to measure the function execution duration. The billing duration starts when the first request starts to be processed and ends when the last request is processed.

Concurrency throttling

By default, the maximum number of on-demand instances of Function Compute in a region is 300. The maximum number of requests that can be processed at the same time in a region is 300 × Instance concurrency. For example, if you set instance concurrency to 10, a maximum of 3,000 concurrent requests can be processed at the same time in a region. If the number of concurrent requests exceeds the maximum number of requests that Function Compute can handle, the throttling control error ResourceExhausted is reported.

Note

To increase the upper limit of on-demand instances in a region, contact us.

Logging

• If instance concurrency is set to 1, Function Compute returns function logs in the X-Fc-Log-Result response header if you specify X-Fc-Log-Type: Tail in the HTTP request header when you invoke a function. If instance concurrency is set to a value greater than 1, the response header does not contain function logs because the logs of a specific request cannot be obtained among concurrent requests.

• For a Node.js runtime, console.info() was used to return logs, which include request IDs. If instance concurrency is set to a value greater than 1, console.info() cannot print request IDs as expected. All the request IDs are printed as req 2. The following example shows a sample log:

  2019-11-06T14:23:37.587Z req1 [info] logger begin
  2019-11-06T14:23:37.587Z req1 [info] ctxlogger begin
  2019-11-06T14:23:37.587Z req2 [info] logger begin
  2019-11-06T14:23:37.587Z req2 [info] ctxlogger begin
  2019-11-06T14:23:40.587Z req1 [info] ctxlogger end
  2019-11-06T14:23:40.587Z req2 [info] ctxlogger end
  2019-11-06T14:23:37.587Z req2 [info] logger end
  2019-11-06T14:23:37.587Z req2 [info] logger end                    

  In this case, we recommend that you use context.logger.info() to print logs. This method allows request IDs to be printed as expected. The following sample code shows an example:

  exports.handler = (event, context, callback) => {
      console.info('logger begin');
      context.logger.info('ctxlogger begin');
  
      setTimeout(function() {
          context.logger.info('ctxlogger end');
          console.info('logger end');
          callback(null, 'hello world');
      }, 3000);
  };                   

Error handling

When an instance concurrently processes multiple requests, unexpected process quits caused by failed requests affect other concurrent requests. Therefore, you must compile logic to capture request-level exceptions in the function code and prevent the impact on other requests. The following example shows sample Node.js code:

exports.handler = (event, context, callback) => {
    try {
        JSON.parse(event);
    } catch (ex) {
        callback(ex);
    }

    callback(null, 'hello world');
};                    

Shared variables

When an instance concurrently processes multiple requests, errors may occur if multiple requests attempt to modify a variable at the same time. You must use mutual exclusion in your code to protect non-thread-safe variables upon modifications. The following example shows the sample Java code:

public class App implements StreamRequestHandler
{
    private static int counter = 0;

    @Override
    public void handleRequest(InputStream inputStream, OutputStream outputStream, Context context) throws IOException {
        synchronized (this) {
            counter = counter + 1;
        }
        outputStream.write(new String("hello world").getBytes());
    }
}                    

Monitoring metrics

After you set instance concurrency to a value greater than 1, you can see that the number of used instances is reduced in the instance monitoring chart.

Additional information

• In addition to the Function Compute console, Function Compute also allows you to use API operations to manage functions. For more information, see Function.

• If the function timeout period elapses, see What do I do if the function execution times out and the error "Function time out after" is reported?

• If it takes a long time to invoke a function that is not frequently used, see Why do functions that are infrequently used take a longer period of time to invoke? To mitigate the impact of cold starts, you can use provisioned instances. For more information, see How to keep instances alive to eliminate the impact of cold starts?

• For more information about how to obtain the Alibaba Cloud Resource Name (ARN) of a function, see Obtain the ARN of a function.