A common issue that affects service performance is connection timeouts caused by slow requests. The slow log feature of ApsaraDB for Redis allows you to find the IP address of the client that sends these requests and troubleshoot issues based on the details of slow logs.
Slow logs record requests that take longer than a specified threshold to execute in ApsaraDB for Redis. Slow logs are classified into slow logs from data nodes and slow logs from proxy nodes.
- If the ApsaraDB for Redis instance uses the standard architecture, only slow logs from data nodes are collected.
- For more information, see Modify the values of parameters for an instance.
|Slow log type||Description||Parameter|
|Slow logs from data nodes|
|Slow logs from proxy nodes||rt_threshold_ms: the threshold of the command execution duration for slow logs from proxy nodes. Default value: 500. Unit: milliseconds. We recommend that you set the threshold to a value close to the client timeout period, which is from 200 milliseconds to 500 milliseconds.|
Methods used to query slow logs
|Slow log type||Method|
|Slow logs from data nodes|
|Slow logs from proxy nodes||Log on to the ApsaraDB for Redis console or call an API operation:|
In most cases, service timeouts are caused by slow requests. We recommend that you perform the following steps to troubleshoot timeout issues:
- If a service timeout issue occurs, first check the slow logs generated on proxy nodes. For more information, see View slow logs. Note
- For standard instances, go to Step 3 and analyze slow logs from data nodes.
- If no slow logs from proxy nodes exist, you can check the network connection between the client and the ApsaraDB for Redis instance.
- Find the command that generated the earliest slow log on proxy nodes. Note If slow requests accumulate on data nodes, these requests are recorded in slow logs from proxy nodes.
In this example, the earliest recorded slow log is generated by the KEYS command. The IP address on the right of the log entry is the IP address of the client that sends the command.
- Check the slow logs from data nodes to find the slow logs from proxy nodes that cause the timeout issue. Note Typically, the command that first generates slow logs on proxy nodes can also generate slow logs on data nodes. The number of slow logs from a data node is usually smaller than that of a proxy node. This is because the two slow log types have different definitions of execution time and slow log thresholds.
In this example, after you view slow logs from proxy nodes, you can find that the slow log generated by the KEYS command also exists on data nodes. No other slow logs that are displayed on the Proxy tab exist on the Data nodes tab. This shows that the KEYS command causes the timeout issue.
- In slow logs from proxy nodes, you can search for the client IP address for optimization based on the command found in Step 2.