This topic describes how to diagnose Classic Load Balancer (CLB) instances. The diagnosis includes the following check items: the instance health, Anti-DDoS status, certificate status, access control status, billing status, and whether the CLB instance is idle. If an exception is detected, the cause and solution are provided.

Procedure for diagnosing a CLB instance

To diagnose a CLB instance, perform the following steps:

  1. Log on to the CLB console.
  2. In the left-side navigation pane, choose Instances > Instances.
  3. Find the CLB instance that you want to diagnose, and click the ID of the CLB instance. You can also click the icon in the Health Check column. On the Instance Details tab, click Health Check in the upper-right corner.
  4. On the Instance Details page, the diagnostic result of the CLB instance is displayed. If an exception is detected, the cause and solution are provided.
  5. Click OK.

Perform a health check

CLB runs health checks by executing scripts that are generated based on the health check configurations of listeners. CLB uses Cloud Assistant to execute scripts on Elastic Compute Service (ECS) instances. If an exception is detected, the cause and solution are provided. To perform health checks on backend servers, make sure that the following requirements are met:

  • Your CLB service is granted the required permissions to perform health checks on ECS instances. To grant the permissions, go to RAM Roles.
  • The backend servers that you want to check must be ECS instances that run Linux, the default Linux shell must be Bash, and Cloud Assistant must have been installed on the ECS instances. In addition, the ECS instances must be deployed in a virtual private cloud (VPC), and they must be in the Running state.
  • Health check is enabled on the CLB listener. One or more ECS instances that are added to the backend server group are declared unhealthy.

Before you perform health checks, take note of the following items:

  • The health check feature is not supported by backend servers that are associated with forwarding rules.
  • Health checks provide you with the causes that may be the reason for the exceptions.
  1. If an exception is detected after a health check is completed, click Health Check.
  2. To view the cause and solution of the exception, click Start Diagnostics in the Actions column.
    If you want to perform health checks on more than five ECS instances, divide these ECS instances into batches. Health checks support the following check items.
    Listener type Status of heath check ports iptables configuration rpfilter configuration Response upon HTTP probing UDP probing
    TCP -
    UDP -
    HTTP -
    HTTPS -
  3. To view the script execution result in details, log on to the Cloud Assistant console, select the region where the ECS instance is deployed, and then click the Tasks tab.