Stress Testing FAQ

Taking users' stress test experiences as reference, this document summarizes common performance issues of stress tests, and provides users with troubleshooting solutions and suggestions for stress test.

Stress Test FAQ

1. The public network traffic is not opened for backend CVMs

When you purchase a CVM, if public network traffic is not opened, the forwarding may fail when the public network cloud load balancer is mounted on the CVM.

2. Bandwidth of Backend CVM is Insufficient

If the bandwidth is set too low for the backend CVM, the backend CVM cannot return packets back to the LB when the bandwidth exceeds the threshold, and LB will return 504 and 502 to the client.

3. Insufficient Client Ports

If there are too few clients or the port range of the client is set too small, it may fail to establish the connection due to insufficient ports. Besides, if the keep_alive field is greater than 0 when a persistent connection is established, the connection will keep occupying the port, thus resulting in insufficient client ports.

4. Backend CVM-based Applications Become Performance Bottleneck

After the request reaches the backend CVM through cloud load balancer, the load on the backend CVM itself is balanced normally, but because all applications on the backend CVM depend on other applications such as databases, performance bottlenecks in the databases may also affect the performance of stress test.

5. The Health Status of the Backend CVM is Exceptional

The health status of the backend CVM tends to be ignored when performing stress test. If there is a health check failure or unstable health check status (sometimes good, sometimes bad and changing repeatedly) for backend CVM, it may lead to low performance of stress test.

6. Session Persistence Enabled for Cloud Load Balancer Results in Uneven Backend CVM Traffic Distribution

After session persistence is enabled for cloud load balancer, requests tend to fall on some backend CVMs. As a result, the traffic distribution is uneven, and the performance of the stress test is affected. It is recommended to disable session persistence when performing stress tests.

Suggestions for Stress Tests

Note: The following settings are only used for stress tests of cloud load balancer. It is not necessary to configure the exact same settings for the user's production environment.

• It is recommended to use short connection to perform stress tests on forwarding capability of cloud load balancer.

In general, except for verifying some features such as session persistence, the stress test is mainly designed to verify the forwarding capability of cloud load balancer. Therefore, the short connection can be used to test the processing capability of LBs and backend CVMs.

• It is recommended to use a persistent connection to perform the stress tests on throughput of cloud load balancer, such as the upper limit of bandwidth, long connection service.

In this case, it is recommended to adjust the timeout value of a stress test tool to a smaller threshold. If the timeout period is too long, the average response time will be longer, which will be detrimental to quickly determine whether the stress test level is reached.

• It is recommended to use a static web page provided by backend CVM for stress test to avoid loss caused by application logic itself, such as I/O, DB.

• Disable session persistence feature for listening. Otherwise, the pressure will be concentrated on individual backend CVMs. In addition, when the pressure performance is not satisfactory, you can determine whether the traffic is evenly distributed by checking the monitor data of backend CVM under cloud load balancer.

• Disable health check feature for listening to reduce access requests to backend CVMs from health check.

• Use multiple clients (> 5) for stress tests. Dispersed source IP is better for simulating the actual situation online.