Services or capabilities described in Amazon Web Services documentation might vary by Region. To see the differences applicable to the China Regions, see Getting Started with Amazon Web Services in China (PDF).

Register targets with your Application Load Balancer target group

You register your targets with a target group. When you create a target group, you specify its target type, which determines how you register its targets. For example, you can register instance IDs, IP addresses, or Lambda functions. For more information, see Target groups for your Application Load Balancers.

If demand on your currently registered targets increases, you can register additional targets in order to handle the demand. When your target is ready to handle requests, register it with your target group. The load balancer starts routing requests to the target as soon as the registration process completes and the target passes the initial health checks.

If demand on your registered targets decreases, or you need to service a target, you can deregister it from your target group. The load balancer stops routing requests to a target as soon as you deregister it. When the target is ready to receive requests, you can register it with the target group again.

When you deregister a target, the load balancer waits until in-flight requests have completed. This is known as connection draining. The status of a target is draining while connection draining is in progress.

When you deregister a target that was registered by IP address, you must wait for the deregistration delay to complete before you can register the same IP address again.

If you are registering targets by instance ID, you can use your load balancer with an Auto Scaling group. After you attach a target group to an Auto Scaling group and the group scales out, the instances launched by the Auto Scaling group are automatically registered with the target group. If you detach the target group from the Auto Scaling group, the instances are automatically deregistered from the target group. For more information, see Attaching a load balancer to your Auto Scaling group in the Amazon EC2 Auto Scaling User Guide.

When shutting down an application on a target you must first deregister the target from its target group and allow time for existing connections to drain. You can monitor deregistration status using the describe-target-health CLI command, or by refreshing the target group view in the Amazon Web Services Management Console. After confirming the target is deregistered you can proceed with stopping or terminating the application. This sequence prevents users from experiencing 5XX errors when applications are terminated while still processing traffic.

Target security groups

When you register EC2 instances as targets, you must ensure that the security groups for your instances allow the load balancer to communicate with your instances on both the listener port and the health check port.

We also recommend that you allow inbound ICMP traffic to support Path MTU Discovery. For more information, see Path MTU Discovery in the Amazon EC2 User Guide.

Shared subnets

Participants can create an Application Load Balancer in a shared VPC. Participants can't register a target that runs in a subnet that is not shared with them.

Register targets

Each target group must have at least one registered target in each Availability Zone that is enabled for the load balancer.

The target type of your target group determines how you register targets with that target group. For more information, see Target type.

Console

To register targets

1. Open the Amazon EC2 console at https://console.amazonaws.cn/ec2/.

2. On the navigation pane, under Load Balancing, choose Target Groups.

3. Choose the name of the target group to open its details page.

4. Choose the Targets tab.

5. Choose Register targets.

6. If the target type of the target group is instance, select available instances, override the default port if needed, and then choose Include as pending below.

7. If the target type of the target group is ip, for each IP address, select the network, enter the IP addresses and ports, and choose Include as pending below.

8. If the target type of the target group is lambda, select the Lambda function or enter its ARN. For more information, see Use Lambda functions as targets.

9. Choose Register pending targets.

Amazon CLI

To register targets

Use the register-targets command. The following example registers targets by instance ID. Because the port is not specified, the load balancer uses the target group port.

aws elbv2 register-targets \
    --target-group-arn target-group-arn \
    --targets Id=i-1234567890abcdef0 Id=i-0abcdef1234567890

The following example registers targets by IP address. Because the port is not specified, the load balancer uses the target group port.

aws elbv2 register-targets \
    --target-group-arn target-group-arn \
    --targets Id=10.0.50.10 Id=10.0.50.20

The following example registers a Lambda function as a target.

aws elbv2 register-targets \
    --target-group-arn target-group-arn \
    --targets Id=lambda-function-arn

CloudFormation

To register targets

Update the AWS::ElasticLoadBalancingV2::TargetGroup resource to include the new targets. The following example registers two targets by instance ID.

Resources:
  myTargetGroup:
    Type: 'AWS::ElasticLoadBalancingV2::TargetGroup'
    Properties:
      Name: my-target-group
      Protocol: HTTP
      Port: 80
      TargetType: instance
      VpcId: !Ref myVPC
      Targets:
        -Id: i-1234567890abcdef0
         Port: 80
        -Id: i-0abcdef1234567890
         Port: 80

Deregister targets

If demand on your application decreases, or if you need to service your targets, you can deregister targets from your target groups. Deregistering a target removes it from your target group, but does not affect the target otherwise.

Console

To deregister targets

1. Open the Amazon EC2 console at https://console.amazonaws.cn/ec2/.

2. On the navigation pane, under Load Balancing, choose Target Groups.

3. Choose the name of the target group to open its details page.

4. On the Targets tab, select the targets to remove.

5. Choose Deregister.

6. When prompted for confirmation, choose Deregister.

Amazon CLI

To deregister targets

Use the deregister-targets command. The following example deregisters two targets that were registered by instance ID.

aws elbv2 deregister-targets \
    --target-group-arn target-group-arn \
    --targets Id=i-1234567890abcdef0 Id=i-0abcdef1234567890