Check the health of your Application Load Balancer targets

You can check the health status of the targets registered with your target groups. For help with health check failures, see Troubleshooting: A registered target is not in service.

Console

To check the health of your targets

1. Open the Amazon EC2 console at https://console.aws.amazon.com/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. The Details tab displays the total number of targets, plus the number of targets for each health status.

5. On the Targets tab, the Status column indicates the status of each target.

6. If the status is any value other than Healthy, the Status details column contains more information.

To receive email notifications about unhealthy targets

Use CloudWatch alarms to trigger a Lambda function to send details about unhealthy targets. For step-by-step instructions, see the following blog post: Identifying unhealthy targets of your load balancer.

AWS CLI

To check the health of your targets

Use the describe-target-health command. This example filters the output to include only targets that are not healthy. For targets that are not healthy, the output includes a reason code.

aws elbv2 describe-target-health \
    --target-group-arn target-group-arn \
    --query "TargetHealthDescriptions[?TargetHealth.State!='healthy'].[Target.Id,TargetHealth.State,TargetHealth.Reason]" \
    --output table

The following is example output.

----------------------------------------------
|            DescribeTargetHealth            |
+--------------+---------+-------------------+
|  172.31.0.57 |  unused |  Target.NotInUse  |
|  172.31.0.50 |  unused |  Target.NotInUse  |
+--------------+---------+-------------------+

Target states and reason codes

The following list shows the possible reason codes for each target state.

Target state is healthy

A reason code is not provided.

Target state is initial

• Elb.RegistrationInProgress - The target is in the process of being registered with the load balancer.

• Elb.InitialHealthChecking - The load balancer is still sending the target the minimum number of health checks required to determine its health status.

Target state is unhealthy

• Target.ResponseCodeMismatch - The health checks did not return an expected HTTP code.

• Target.Timeout - The health check requests timed out.

• Target.FailedHealthChecks - The load balancer received an error while establishing a connection to the target or the target response was malformed.

• Elb.InternalError - The health checks failed due to an internal error.

Target state is unused

• Target.NotRegistered - The target is not registered with the target group.

• Target.NotInUse - The target group is not used by any load balancer or the target is in an Availability Zone that is not enabled for its load balancer.

• Target.InvalidState - The target is in the stopped or terminated state.

• Target.IpUnusable - The target IP address is reserved for use by a load balancer.

Target state is draining

• Target.DeregistrationInProgress - The target is in the process of being deregistered and the deregistration delay period has not expired.

Target state is unavailable

• Target.HealthCheckDisabled - Health checks are disabled for the target group.