MySQL 8.0 Release Notes
MySQL 8.0 Source Code Documentation
This section describes which server options configure the default error log destination, which can be the console or a named file. It also indicates which log sink components base their own output destination on the default destination.
In this discussion, “console” means
stderr, the standard error output. This is
your terminal or console window unless the standard error output
has been redirected to a different destination.
The server interprets options that determine the default error
log destination somewhat differently for Windows and Unix
systems. Be sure to configure the destination using the
information appropriate to your platform. After the server
interprets the default error log destination options, it sets
the log_error system variable
to indicate the default destination, which affects where several
log sink components write error messages. The following sections
address these topics.
On Windows, mysqld uses the
--log-error,
--pid-file, and
--console options to determine
whether the default error log destination is the console or a
file, and, if a file, the file name:
If
--consoleis given, the default destination is the console. (--consoletakes precedence over--log-errorif both are given, and the following items regarding--log-errordo not apply.)If
--log-erroris not given, or is given without naming a file, the default destination is a file namedhost_name.err--pid-fileoption is specified. In that case, the file name is the PID file base name with a suffix of.errin the data directory.If
--log-erroris given to name a file, the default destination is that file (with an.errsuffix added if the name has no suffix). The file location is under the data directory unless an absolute path name is given to specify a different location.
If the default error log destination is the console, the
server sets the log_error
system variable to stderr. Otherwise, the
default destination is a file and the server sets
log_error to the file name.
On Unix and Unix-like systems, mysqld uses
the --log-error option to
determine whether the default error log destination is the
console or a file, and, if a file, the file name:
If
--log-erroris not given, the default destination is the console.If
--log-erroris given without naming a file, the default destination is a file namedhost_name.errIf
--log-erroris given to name a file, the default destination is that file (with an.errsuffix added if the name has no suffix). The file location is under the data directory unless an absolute path name is given to specify a different location.If
--log-erroris given in an option file in a[mysqld],[server], or[mysqld_safe]section, on systems that use mysqld_safe to start the server, mysqld_safe finds and uses the option, and passes it to mysqld.
Note
It is common for Yum or APT package installations to
configure an error log file location under
/var/log with an option like
log-error=/var/log/mysqld.log in a server
configuration file. Removing the path name from the option
causes the
host_name.err
If the default error log destination is the console, the
server sets the log_error
system variable to stderr. Otherwise, the
default destination is a file and the server sets
log_error to the file name.
After the server interprets the error log destination
configuration options, it sets the
log_error system variable to
indicate the default error log destination. Log sink
components may base their own output destination on the
log_error value, or determine
their destination independently of
log_error
If log_error is
stderr, the default error log destination
is the console, and log sinks that base their output
destination on the default destination also write to the
console:
log_sink_internal,log_sink_json,log_sink_test: These sinks write to the console. This is true even for sinks such aslog_sink_jsonthat can be enabled multiple times; all instances write to the console.log_sink_syseventlog: This sink writes to the system log, regardless of thelog_errorvalue.
If log_error is not
stderr, the default error log destination
is a file and log_error
indicates the file name. Log sinks that base their output
destination on the default destination base output file naming
on that file name. (A sink might use exactly that name, or it
might use some variant thereof.) Suppose that the
log_error value
file_name. Then log sinks use the
name like this:
log_sink_internal,log_sink_test: These sinks write tofile_name.log_sink_json: Successive instances of this sink named in thelog_error_servicesvalue write to files namedfile_nameplus a numbered.suffix:NN.jsonfile_name.00.jsonfile_name.01.jsonlog_sink_syseventlog: This sink writes to the system log, regardless of thelog_errorvalue.