Why does ELB frequently send probe requests to backend ECSs due to health check?

ELB adopts an HA cluster deployment mode. All forwarding nodes in the cluster simultaneously send probe requests to the backend ECSs. You can configure inspection intervals and health check will be performed according to the intervals. As a result, probe requests will be sent every few seconds. You can configure the health check interval to control the frequency of access to backend ECSs.

Do maximum retries include health checks that consider backend servers unhealthy?

Yes. Maximum retries are the maximum number of health checks after which a backend server is detected healthy or unhealthy.

When does a health check start?

After a backend server is added to a backend server group, the health check is performed at a random time during the first interval and then at the Check Interval .

How do I troubleshoot an unhealthy backend server?

Symptom: If a client cannot access a backend server through a load balancer, the health check results for the backend server is Unhealthy on Backend Server Group of the load balancer details page.

ELB health check is conducted by sending heartbeat check to backend servers. Troubleshooting Procedure:

Check whether the backend server group is associated with a listener.
Check whether ELB is bound to an EIP or a private IP.
Configure health check.
Check the configuration of the server security group.
Check the subnet ACL configuration.
Check the firewall configuration of the backend server.
Check the route configuration of the backend server.
Check the load of the backend server.

Elastic Load Balancing

Health Check