Server Load Balancer:Specify a function from Function Compute as a backend server for ALB

Key features

• Serverless architecture: Adding a Function Compute function as a backend service to ALB allows you to easily build serverless applications and reduce O&M costs.

• Auto scaling: Function Compute automatically scales computing resources up or down based on traffic, ensuring sufficient computing power during traffic spikes and saving resources during traffic troughs.

• High availability and fault tolerance: ALB and Function Compute together provide high availability and disaster recovery capabilities, ensuring stable application operation.

Use scenarios

• Microservices architecture: Through the advanced forwarding capabilities of ALB, requests are distributed to different microservice functions. Function Compute auto scales its resources to handle high concurrency requests, improving system scalability and reliability.

• Real-time data processing: With ALB distributing requests to required functions, you only need to write a few lines of code and perform basic configuration. Then, Function Compute can process your business data in real time.

• Event-driven requests: ALB checks for and forwards event-triggered requests to associated functions. Function Compute processes the requests and stores the processing results in a database or sends them to other services, enabling an event-driven architecture.

• Image and video processing: ALB checks for and forwards image and video upload requests to processing functions. Function Compute auto scales computing resources based on task sizes, ensuring efficient completion of image and video processing tasks.

Limitations

• For regions where Function Compute is supported as backend servers for ALB, see Regions and zones.

• The ALB instance and the function you want to use as a backend server must be deployed in the same region.

• For an ALB server group of the Function Compute type, only one function can be added as the backend server.

• For Function Compute 2.0, if you set the Handler Type of a function to Event Handler, and use the function as an ALB backend server, an HTTP trigger must be configured for the function.

Step 1: Create a function

1. Log on to the Function Compute console. In the left-side navigation pane, choose Functions. On the Functions page, select a region in the top navigation bar, then click Create Function.

2. On the Create Function page, select a function type, complete the function code configuration, then click Create.

   In this example, the Event Function type is selected and the default Code configuration of the Use Sample Code method is used. You can keep the default values for other Event Function parameters or set them as needed.

   

3. On the function details page, on the Code tab, click Test Function.

   When the Successful Execution message is displayed, you can view the function execution result in the Response section. In this example, the response is hello world.

Step 2: Create a server group of the Function Compute type

1. 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.

2. In the Create Server Group dialog box, select Function Compute for Server Group Type, then click Create.

   Important

   If you enable health checks for this server group, health check probes are counted as requests to Function Compute, and Function Compute charges for these requests.

   

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

4. In the Add Backend Server panel, select the created function, then click OK.

   In this topic, Configuration Method is set to Service, the created function is selected for Function Name, and Version is set to LATEST. If you need to configure by ARN, you need to obtain the Alibaba Cloud Resource Name (ARN) of the function.

   

Step 3: Create a listener

1. In the left-side navigation pane, choose ALB > Instances, then click the ID of the instance you want.

2. Click the Listener tab, then click Create Listener.

3. On the Configure Listener wizard page, set the listener protocol and port, then click Next.

   In this topic, the HTTP protocol and port 80 are selected. You can keep the default values for other HTTP listener parameters or set them as needed.

   

4. On the Select Server Group wizard page, select Function Compute from the Select Server Group drop-down list, select the created server group, then click Next.

   

5. On the Configuration Review wizard page, confirm the configuration, then click Submit.

Step 4: Configure domain name resolution

In real-world business scenarios, we recommend that you use a custom domain name and resolve it to the domain name of your ALB instance with a CNAME record.

1. In the left-side navigation pane, choose ALB > Instances. On the Instances page, copy the DNS name of your ALB instance.

2. Add a CNAME record:

   1. On the Authoritative DNS Resolution page in the Alibaba Cloud DNS console, find the custom domain name you want, and click DNS Settings in the Actions column.

      Note

      For domain names not registered on Alibaba Cloud, you need to add the domain name to Alibaba Cloud DNS before you can configure domain name resolution.

   2. On the resolution settings page, click Add DNS Record, configure the CNAME record, then click OK.

      In this topic, Record Type is set to CNAME, and Record Value is set to the DNS name of the ALB instance. You can keep the default values for other DNS record parameters or set them as needed.

      

Step 5: Test the load balancing effect

With the above steps finished, a connection is established between ALB and Function Compute. Open a command line window and run the curl <Custom domain name> command to test the connectivity between ALB and Function Compute.

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