Using libcoredumper

Availability:This feature is Experimental quality.

This feature was implemented in Percona Server for MySQL 5.7.31-34 and has been tested against the supported operating systems for this version. The tool is experimental and may not be tested against newer operating systems in the future.

The documented moment of a computer when either the computer or an application crashed is a core dump file. Developers examine the dump as one of the tasks when searching for the cause of a failure.

The libcoredumper is a free and Open Source fork of google-coredumper, enhanced to work on newer Linux versions, and GCC and CLANG.

You should test before putting this tool into production.

Enabling the libcoredumper

Enable core dumps for troubleshooting purposes.

To enable the libcoredumper, add the coredumper variable to the mysqld section of my.cnf. This variable is independent of the older core-file variable.

The variable can have the following possible values:

Value Description
Blank The core dump is saved under MySQL datadir and named core.
A path ending with / The core dump is saved under the specified directory and named core.
Full path with a filename The core dump is saved under the specified directory and with the specified filename

Restart the server.

Verifying the libcoredumper is Active

MySQL writes to the log when generating a core file and delegates the core dump operation to the Linux kernel. An example of the log message is the following:

Writing a core file

MySQL using the libcoredumper to generate the file creates the following message in the log:

Writing a core file using lib coredumper

Every core file adds a crash timestamp instead of a PID for the following reasons:

  • Lets you correlate the core file with a crash. MySQL prints a UTC timestamp on the crash log.

    10:02:09 UTC - mysqld got signal 11;
    
  • Lets you keep multiple core files.

Note

For example, operators and containers run as PID 1. If the process ID identified the core file, each container crash generates a core dump that overwrites the previous core file.

Disabling the libcoredumper

You can disable the libcoredumper. A core file may contain sensitive data and takes disk space.

To disable the libcoredumper you must do the following:

  1. In the mysqld section of my.cnf, remove the libcoredumper variable.
  2. Restart the server.

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