Use DescribeTargetHealth with an AWS SDK or CLI

    /// <summary>
    /// Get the target health for a group by name.
    /// </summary>
    /// <param name="groupName">The name of the group.</param>
    /// <returns>The collection of health descriptions.</returns>
    public async Task<List<TargetHealthDescription>> CheckTargetHealthForGroup(string groupName)
    {
        List<TargetHealthDescription> result = null!;
        try
        {
            var groupResponse =
                await _amazonElasticLoadBalancingV2.DescribeTargetGroupsAsync(
                    new DescribeTargetGroupsRequest()
                    {
                        Names = new List<string>() { groupName }
                    });
            var healthResponse =
                await _amazonElasticLoadBalancingV2.DescribeTargetHealthAsync(
                    new DescribeTargetHealthRequest()
                    {
                        TargetGroupArn = groupResponse.TargetGroups[0].TargetGroupArn
                    });
            ;
            result = healthResponse.TargetHealthDescriptions;
        }
        catch (TargetGroupNotFoundException)
        {
            Console.WriteLine($"Target group {groupName} not found.");
        }
        return result;
    }

Example 1: To describe the health of the targets for a target group

The following describe-target-health example displays health details for the targets of the specified target group. These targets are healthy.

aws elbv2 describe-target-health \
    --target-group-arn arn:aws:elasticloadbalancing:us-west-2:123456789012:targetgroup/my-targets/73e2d6bc24d8a067

Output:

{
    "TargetHealthDescriptions": [
        {
            "HealthCheckPort": "80",
            "Target": {
                "Id": "i-ceddcd4d",
                "Port": 80
            },
            "TargetHealth": {
                "State": "healthy"
            }
        },
        {
            "HealthCheckPort": "80",
            "Target": {
                "Id": "i-0f76fade",
                "Port": 80
            },
            "TargetHealth": {
                "State": "healthy"
            }
        }
    ]
}

Example 2: To describe the health of a target

The following describe-target-health example displays health details for the specified target. This target is healthy.

aws elbv2 describe-target-health \
    --targets Id=i-0f76fade,Port=80 \
    --target-group-arn arn:aws:elasticloadbalancing:us-west-2:123456789012:targetgroup/my-targets/73e2d6bc24d8a067

Output:

{
    "TargetHealthDescriptions": [
        {
            "HealthCheckPort": "80",
            "Target": {
                "Id": "i-0f76fade",
                "Port": 80
            },
            "TargetHealth": {
                "State": "healthy"
            }
        }
    ]
}

The following example output is for a target whose target group is not specified in an action for a listener. This target can't receive traffic from the load balancer.

{
    "TargetHealthDescriptions": [
    {
        "HealthCheckPort": "80",
        "Target": {
            "Id": "i-0f76fade",
            "Port": 80
        },
            "TargetHealth": {
                "State": "unused",
                "Reason": "Target.NotInUse",
                "Description": "Target group is not configured to receive traffic from the load balancer"
            }
        }
    ]
}

The following example output is for a target whose target group was just specified in an action for a listener. The target is still being registered.

{
    "TargetHealthDescriptions": [
        {
            "HealthCheckPort": "80",
            "Target": {
                "Id": "i-0f76fade",
                "Port": 80
            },
            "TargetHealth": {
                "State": "initial",
                "Reason": "Elb.RegistrationInProgress",
                "Description": "Target registration is in progress"
            }
        }
    ]
}

The following example output is for an unhealthy target.

{
    "TargetHealthDescriptions": [
        {
            "HealthCheckPort": "80",
            "Target": {
                "Id": "i-0f76fade",
                "Port": 80
            },
            "TargetHealth": {
                "State": "unhealthy",
                "Reason": "Target.Timeout",
                "Description": "Connection to target timed out"
            }
        }
    ]
}

The following example output is for a target that is a Lambda function and health checks are disabled.

{
    "TargetHealthDescriptions": [
        {
            "Target": {
                "Id": "arn:aws:lambda:us-west-2:123456789012:function:my-function",
                "AvailabilityZone": "all",
            },
            "TargetHealth": {
                "State": "unavailable",
                "Reason": "Target.HealthCheckDisabled",
                "Description": "Health checks are not enabled for this target"
            }
        }
    ]
}

    // Checks the health of the instances in the target group.
    public List<TargetHealthDescription> checkTargetHealth(String targetGroupName) {
        DescribeTargetGroupsRequest targetGroupsRequest = DescribeTargetGroupsRequest.builder()
                .names(targetGroupName)
                .build();

        DescribeTargetGroupsResponse tgResponse = getLoadBalancerClient().describeTargetGroups(targetGroupsRequest);

        DescribeTargetHealthRequest healthRequest = DescribeTargetHealthRequest.builder()
                .targetGroupArn(tgResponse.targetGroups().get(0).targetGroupArn())
                .build();

        DescribeTargetHealthResponse healthResponse = getLoadBalancerClient().describeTargetHealth(healthRequest);
        return healthResponse.targetHealthDescriptions();
    }

  const { TargetHealthDescriptions } = await client.send(
    new DescribeTargetHealthCommand({
      TargetGroupArn: TargetGroups[0].TargetGroupArn,
    }),
  );

Example 1: This example returns the health status of the Targets present in the specified Target Group.

Get-ELB2TargetHealth -TargetGroupArn 'arn:aws:elasticloadbalancing:us-east-1:123456789012:targetgroup/test-tg/a4e04b3688be1970'

Output:

HealthCheckPort Target                                                TargetHealth
--------------- ------                                                ------------
80              Amazon.ElasticLoadBalancingV2.Model.TargetDescription Amazon.ElasticLoadBalancingV2.Model.TargetHealth

class ElasticLoadBalancerWrapper:
    """Encapsulates Elastic Load Balancing (ELB) actions."""

    def __init__(self, elb_client: boto3.client):
        """
        Initializes the LoadBalancer class with the necessary parameters.
        """
        self.elb_client = elb_client


    def check_target_health(self, target_group_name: str) -> List[Dict[str, Any]]:
        """
        Checks the health of the instances in the target group.

        :return: The health status of the target group.
        """
        try:
            tg_response = self.elb_client.describe_target_groups(
                Names=[target_group_name]
            )
            health_response = self.elb_client.describe_target_health(
                TargetGroupArn=tg_response["TargetGroups"][0]["TargetGroupArn"]
            )
        except ClientError as err:
            log.error(f"Couldn't check health of {target_group_name} target(s).")
            error_code = err.response["Error"]["Code"]
            if error_code == "LoadBalancerNotFoundException":
                log.error(
                    "Load balancer associated with the target group was not found. "
                    "Ensure the load balancer exists, is in the correct AWS region, and "
                    "that you have the necessary permissions to access it.",
                )
            elif error_code == "TargetGroupNotFoundException":
                log.error(
                    "Target group was not found. "
                    "Verify the target group name, check that it exists in the correct region, "
                    "and ensure it has not been deleted or created in a different account.",
                )
            log.error(f"Full error:\n\t{err}")
        else:
            return health_response["TargetHealthDescriptions"]