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Why ClickHouse default logging setting is verbose?

· One min read

One thing that often confuses new users is that ClickHouse generates a lot of log output, even under light load.

This is because the default log level is for historical reasons 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 goes wrong.

On the other hand, large volumes of logging means that system table system.text_log fills up quickly and needs to be merged in the background.

If the database runs stable, users may re-configure the log level.

Change log level​

The different log level available are documented here

Edit the ClickHouse server configuration file (/etc/clickhouse-server/config.xml) to modify the log level.

Default value is trace, change it to the desired level.

<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>