This topic describes how to check the status of Server Load Balancer (SLB) instances, specifically by viewing the results of health assessment, Anti-DDoS Basic status check, certificate status detection, access control detection, billing status detection, and idle instance detection. If an exception is detected, the cause and standard solution are provided.

Health checks of SLB instances

To check the status of an SLB instance, follow these steps:

  1. Log on to the Server Load Balancer console.
  2. In the left-side navigation pane, choose Instances > Server Load Balancer.
  3. Find the target SLB instance and click in the Health Check column. Optionally, you can click the ID of the target SLB instance and on the instance details page that appears, click Health Check in the upper-right corner.
  4. On the health check details page, the health check result of the target SLB instance is displayed. If an exception is detected, the cause and solution are provided.
  5. Click OK.

Health check diagnostics

SLB provides a health check diagnostics function for backend servers (Elastic Compute Service instances). This function is realized by running detection scripts on backend servers through Cloud Assistant. The scripts are generated by SLB based on the health check configurations of the listener. If an exception is detected, the cause and solution are also provided. Before you perform health check diagnostics, make sure that the following conditions are met:

  • Permissions are granted to SLB to perform health check diagnostics on backend servers. To grant permissions, go to the RAM role authorization page.
  • The backend server to be checked must be an Elastic Compute Service (ECS) instance that is of the VPC type and installed with a Linux system. Also, the ECS instance must be in the running state and the default shell is bash. The Cloud Assistant is installed.
  • The health check function is enabled for the SLB listener. ECS instances are added to the backend server group.

Consider the following before you perform health check diagnostics:

  • Health check diagnostics is not supported by backend servers that are associated with forwarding rules.
  • Health Check diagnostics provides you with the causes that may cause the health check exceptions.
  1. If an exception is detected after you complete the preceding health check steps, click Health Check.
  2. Click Start Diagnostics in the Actions column and view the cause and troubleshooting solution of the exception.
    You can perform health check diagnostics on a maximum of five ECS instances at a time. If the number of instances exceeds this limit, you can perform diagnostics in multiple times. The health check diagnostics function supports the following diagnostic items:
    Listener type Health check port status iptables configuration rpfilter configuration HTTP detection response UDP detection
    TCP -
    UDP -
    HTTP -
    HTTPS -
  3. To query the script running information, log on to Cloud Assistant, select the region of the target ECS instance, and click the Tasks tab.