How do I enable DEBUG logging just for slow queries?

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tonazeem_142892 asked Nov 23, '21 Erick Ramirez answered Nov 23, '21

How do I enable DEBUG logging just for slow queries?

The debugging level is set at INFO, I want to enable logging of slow running queries for which slow_query_log_timeout_in_ms is set. If debugging level will be set to DEBUG, it will log queries running longer than slow_query_log_timeout_in_ms but at the same time lot of other debugging info will be logged. I do not want any debug info other than slow running query, is it possible to only enable logging of slow running queries and nothing else at debug level?

[cassandra@localhost ~]$ nodetool getlogginglevels
Logger Name                                        Log Level
...
org.apache.cassandra                                    INFO

slow query logging

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Answer 1 · 2021-11-23T10:41:06Z

Erick Ramirez answered Nov 23, '21

Debug logging is enabled by default since Cassandra 2.2 and goes to debug.log. This is to reduce the "noise" that goes into system.log.

It is possible to disable debug logging by removing the appender in conf/logback.xml but it is not recommended. Debug logs are crucial if you are investigating an issue or need to understand what is going on with your system so it's recommended to always have it on.

If you want to go against best practice, disable debug logging and set the logging level for the class org.apache.cassandra.db.monitoring to DEBUG. Note that this isn't persistent and you will need to set it every time Cassandra is restarted. Cheers!

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