When your Classic Load Balancer (CLB) instance encounters issues, use the instance diagnostics module to diagnose the CLB instance based on the following check items: instance health, instance capacity, certificates, security policies, billing, listeners, and whether the instance is idle. If an exception is detected, the cause and solution are provided.
Prerequisites
If this is the first time you diagnose a CLB instance, the system automatically creates the service-linked role AliyunServiceRoleForNis. For more information, see service-linked roles.
Diagnose a CLB instance
Go to CLB console - Instances.
Use one of the following methods to diagnose a CLB instance:
Click Start Diagnostics in the Instance Diagnostics column of the CLB instance.
Click the ID of the CLB instance. On the instance details page, choose More > Instance Diagnostics in the upper-right corner.
In the Instance Diagnostics panel, select Show All Diagnostic Items to display all diagnostic items that are supported by CLB.
Diagnostic items
Related operations
You can perform the following operations on the Instance Diagnostics page:
View a diagnostic report
Find the instance whose diagnostic report you want to view and click View Report in the Actions column. Then, you can view the report in the Diagnostic Details panel.
Analyze an instance again
To analyze an instance again, click Re-diagnose in the Actions column of the instance.
Delete the diagnostic records of an instance
To delete all diagnostic records of an instance, click Delete in the Actions column of the instance. In the message that appears, click OK.
FAQ
Can the instance diagnostics module diagnose the historical status of an instance within a specified time period?
No, the instance diagnostics module cannot diagnose the historical status of an instance within a specified time period.
This module can diagnose the status of an instance only within the time period from the current time to 15 minutes earlier.
For example, a CLB instance becomes unavailable at 09:00:00 and recovers at 09:30:00. If you diagnose the CLB instance at 10:00:00, the module can diagnose the status of the instance only from 09:45:00 to 10:00:00. The module cannot identify the cause of the exception that occurs from 09:00:00 to 09:30:00.
Why does the diagnostic result show that the status of the health check feature is abnormal after I diagnose a CLB instance that is configured with health checks? Can I use the instance diagnostics module to identify the cause of an exception?
You can use the instance diagnostics module to diagnose the health check configurations of the listeners that are configured for a CLB instance. If health checks are not configured or a backend server is unhealthy, the health check status of the CLB instance is diagnosed as abnormal.
If the health check status of a CLB instance is abnormal, you can use the further diagnostics feature to identify the cause. For example, if backend services are not enabled on the listener ports of your CLB instance or network filtering settings such as iptables are configured in the operating system of the backend servers that are associated with your CLB instance, you can use the further diagnostics feature to identify the cause.
Why cannot I use the further diagnostics feature on specific CLB backend servers?
You can use the further diagnostics feature only on CLB backend servers that run CentOS, Ubuntu, and Alibaba Cloud Linux. This feature does not support CLB backend servers that run other operating systems such as Windows.
References
To troubleshoot common CLB issues, see FAQs about CLB instances.
Application Load Balancer (ALB) and Network Load Balancer (NLB) also support instance diagnostics. For more information, see Diagnose ALB instances and Diagnose an NLB instance.