Why is ClickHouse logging so verbose by default?
Verbose Logging
One thing that often confuses new users is that ClickHouse generates a lot of logging output, even under light load.
This is because the default logging level, due to historical reasons, is trace (instead of warning that would be the default in other databases).
The ClickHouse developers argue that trace provides a lot of insight in case something goes wrong.
On the other hand, large volumes of logging mean that the system table system.text_log fills up quickly and needs to be merged in the background.
If the database runs stably, users may re-configure the log level, which we explain how to do below.
Change the log level
The different log levels available are documented here
You'll need to edit the ClickHouse server configuration file (/etc/clickhouse-server/config.xml) to modify the log level.
The default value is trace but you can change it to the desired level. See the comment below:
<clickhouse>
<logger>
<!-- Possible levels [1]:
- none (turns off logging)
- fatal
- critical
- error
- warning
- notice
- information
- debug
- trace
- test (not for production usage)
[1]: https://github.com/pocoproject/poco/blob/poco-1.9.4-release/Foundation/include/Poco/Logger.h#L105-L114
-->
<level>trace</level>
... Rest of the configuration file
</clickhouse>