Function Compute:ALB triggers

Limits

• The ALB instance and the Function Compute service must be in the same region.

• The following limits apply when you use Function Compute as a backend server for ALB:

  • Only functions that are triggered by HTTP requests are supported.

  • Function Compute requires that the HTTP request header from the client contains the Date field when a function is accessed. The Date field indicates the time when the message was sent.

• The following limits apply when you use Function Compute with ALB:

  • In ALB, you must set the server group type to Function Compute. The backend server group and the listener must use the HTTP protocol.

  • ALB supports adding only one Function Compute service as a backend server.

Step 1: Write and test the function code

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 the name of the desired function.

4. On the function details page, click the Function Code tab. Write the code in the code editor and click Deploy Code.

   The following code provides an example.

   var getRawBody = require('raw-body');
   var getFormBody = require('body/form');
   var body = require('body');
   
   
   /*
   To enable the initializer feature
   please implement the initializer function as below: 
   exports.initializer = (context, callback) => {
     console.log('initializing');
     callback(null, '');
   };
   */
   
   exports.handler = (req, resp, context) => {
       console.log('hello world');
   
       var params = {
           path: req.path,
           queries: req.queries,
           headers: req.headers,
           method : req.method,
           requestURI : req.url,
           clientIP : req.clientIP,
           log : ("Hello World.This is FC!"),
       }
   
       getRawBody(req, function(err, body) {
           for (var key in req.queries) {
             var value = req.queries[key];
             resp.setHeader(key, value);
           }
           resp.setHeader("Content-Type", "text/plain");
           params.body = body.toString();
           resp.send(JSON.stringify(params, null, '    '));
       });
   
       /*
       getFormBody(req, function(err, formBody) {
           for (var key in req.queries) {
             var value = req.queries[key];
             resp.setHeader(key, value);
           }
           params.body = formBody;
           console.log(formBody);
           resp.send(JSON.stringify(params));
       });
       */
   }

5. On the Function Code tab, click Test Function.

   After the execution is complete, you can view the result at the top of the Function Code tab.

Step 2: Create a server group for Function Compute

1. Log on to the ALB console.

2. Go to the ALB console, in the left-side navigation pane, choose Server Groups. In the top navigation bar, select the same region as the created function, then click Create Server Group.

3. In the navigation pane on the left, choose .

4. On the Server Groups page, click Create Server Group, complete the following configurations, and then click Create.

   

   Configuration item	Description
   Server Group Type	Select the type of the server group. In this example, select Function Compute Type.
   Server Group Name	Custom
   Backend Protocol	Select a backend protocol. In this example, select HTTP.
   Select resource group	Select the resource group to which the server group belongs.
   Configure Health Checks
   Enable Health Check	Enable or disable health checks. In this example, the default setting is used, which is to disable health checks.
   Advanced Configuration	To enable health checks, modify the advanced configurations as needed. For more information, see Create and manage server groups.

5. In the message that is displayed, click Add Backend Server.

6. On the Backend Servers tab, click Configure Function Compute.

7. In the Add Backend Servers panel, use one of the following methods to complete the configuration, and then click OK.

   • Select Resources

     Configuration item	Description
     Configuration Method	Select Select Resources.
     Service	Select the service to which the target function belongs.
     Version	Select LATEST. A newly created service has only the LATEST version by default.
     Function	Select the target function.
     Description	Custom.

   • Use ARN

     Configuration item	Description
     Configuration Method	Select Use ARN.
     ARN	Enter the ARN of the target function. For more information about how to obtain the function ARN, see Obtain the ARN of a function.
     Note:	Custom

   The Add Backend Servers panel displays a message indicating that the server was added successfully. Click Close. On the Backend Servers tab, you can view the configured backend server.

Step 3: Create an ALB instance and configure a listener

1. Log on to the Application Load Balancer (ALB) console.

2. In the top menu bar, select a region. In this example, China (Hangzhou) is selected.

3. On the Instances page, click Create Application Load Balancer.

4. On the Application Load Balancer (Pay-As-You-Go) purchase page, complete the parameter settings.

   This section lists only the parameters that are relevant to this topic. For information about other parameters, see Create and manage an ALB instance.

   • Region: In this example, select China (Hangzhou).

   • Network Type: In this example, select Internet.

5. On the Instances page, find the created ALB instance. In the Actions column of the instance, click Create Listener to open the listener configuration wizard.

6. In the Configure Listener wizard, complete the following configurations, and then click Next.

   Configuration item	Description
   Listener Protocol	Select the protocol for the listener. In this example, select HTTP.
   Listener Port	Enter the listener port that receives requests and forwards them to backend servers. The port range is 1 to 65535. In this example, enter 80.
   Listener Name	Custom
   Advanced Configuration	In this example, the default configurations are used.

7. In the Select Server Group wizard, from the Select Server Group drop-down list, select Function Compute Type. Select the backend server group that you created in Step 2: Create a server group for Function Compute, and then click Next.

8. In the Configuration Review wizard, confirm the settings and click Submit.

Step 4: Test the connection

After you complete the preceding steps, a connection is established between Function Compute and ALB. Perform the following operations to test the connection between Function Compute and ALB.

1. Open a command-line window and run the curl -v command to obtain the Date header field.

   Function Compute requires that the HTTP request header contains the Date field.

   curl -v <ALB instance domain name>

   

2. Run the curl -H command to access the domain name of the ALB instance.

   curl -H "Date header field" <ALB instance domain name>

   If you receive a response message as shown in the following figure, it indicates that ALB can forward requests to Function Compute and invoke the function.

More information

To modify or delete the created trigger, see Manage triggers.