Function Compute:Configure a custom health check policy for instances

Limits

You can configure health check policies only for the function instances that run in custom runtime environments and instances that are started by using custom images.

Health check behaviors

Instance startup

For more information about how to configure Threshold for Successful Detections and Maximum Failures, see Configure a health check policy in the Function Compute console.

Single health check

Allocation after an instance fails the health check

Configure a health check policy in the Function Compute console

This topic describes how to configure a health check policy for a function that is created from Use Custom Runtime and whose Runtime Environments is Node.js 14 and Request Type is Event Requests.

Step 1: Create a function

1. Log on to the Function Compute console. In the left-side navigation pane, click Services & Functions.
2. In the top navigation bar, select a region. On the Services page, click the desired service.
3. On the Functions page, click Create Function.
4. On the Create Function page, select Use Custom Runtime, configure the parameters based on your business requirements, and then click Create.
   The following table describes the parameters that you must configure. Retain the default values for other parameters.

   Parameter	Description
   Function Name	Enter a name for the function.
   Request Type	Select Event Request.
   Runtime Environments	Select Node.js 14.

5. On the function details page, click the Code tab, edit the function code in the code editor, and then deploy the code and run the function.
   The following example provides the sample code for index.js:

   'use strict';
   
   // Constants
   const PORT = 9000;
   const HOST = '0.0.0.0';
   const REQUEST_ID_HEADER = 'x-fc-request-id'
   
   const express = require('express');
   const bodyParser = require('body-parser');
   const app = express();
   
   app.use(bodyParser.urlencoded({ extended: true }));
   app.use(bodyParser.json());
   app.use(bodyParser.raw());
   
   app.get('/readyz', (req, res) => {
     console.log(`receive health check`);
     res.status(200);
     console.log(`i am ready`);
     res.send('i am ready\n');
   });
   
   // invocation
   app.post('/invoke', (req, res) => {
     var rid = req.headers[REQUEST_ID_HEADER]
     console.log(`FC Invoke Start RequestId: ${rid}`)
     res.send('OK');
     console.log(`FC Invoke End RequestId: ${rid}`)
   });
   
   var server = app.listen(PORT, HOST);
   console.log(`Running on http://${HOST}:${PORT}`);
   
   server.timeout = 0; // never timeout
   server.keepAliveTimeout = 0; // keepalive, never timeout

   In the preceding code, readyz is the handler of the defined health check policy to process HTTP GET requests in the /readyz path. After you complete Step 2, you can configure this handler to run periodically to check whether the instance is normal.

   Function Compute attempts to allocate another instance when it determines that the function instance is abnormal. If Function Compute fails to allocate another instance, a health check error is returned.

   For example, if you replace the code snippets for health check in the preceding sample code with the following code, the 500 error code is returned.

   app.get('/readyz', (req, res) => {
     console.log(`receive health check`);
     res.status(500);
     console.log(`i am not ready`);
     res.send('i am not ready\n');
   });

   The following information is returned if the function is run again.

   {
       "ErrorCode": "FunctionNotStarted",
       "ErrorMessage": "check function health failed with status code: 500 "
   }

Step 2: Configure a health check policy for instances

1. Log on to the Function Compute console. In the left-side navigation pane, click Services & Functions.
2. In the top navigation bar, select a region. On the Services page, click the desired service.
3. On the Functions page, find the desired function and click Configure in the Actions column.
4. In the Health Check Settings section, configure the parameters and click Save. The following table describes the parameters.

   Parameter	Description
   Health Check	Specify whether to enable the health check feature. If you select Enable, you must configure the following parameters:
   Request Path	The HTTP GET path for the health checks. Function Compute sends HTTP GET requests to this path for health checks. The value must start with a forward slash (/).
   Delay for First Detection	Specify the time to wait before the first health check.
   Detection Interval	Specify the interval at which HTTP GET requests are sent.
   Timeout Period	Specify the timeout period of HTTP GET requests. When the timeout period elapses, the requests are considered to have failed.
   Maximum Failures	Specify the threshold for HTTP GET request failures. When the number of consecutive failed HTTP GET requests reaches the specified value during a periodic health check, the instance is considered to have failed the health check.
   Threshold for Successful Detections	The success threshold for HTTP GET requests. When the number of consecutive successful HTTP GET requests reaches this value, the instance is considered to have passed the health check.

Additional information