The syslog-ng 3.0 Administrator Guide

Do not base the separation of log messages into different files on the facility parameter. As several applications and processes can use the same facility, the facility does not identify the application that sent the message. By default, the facility parameter is not even included in the log message itself. In general, sorting the log messages into several different files can make finding specific log messages difficult. If you must create separate log files, use the application name.

Standard log messages include the local time of the sending host, without any time zone information. It is recommended to replace this timestamp with an ISODATE timestamp, because the ISODATE format includes the year and timezone as well. To convert all timestamps to the ISODATE format, include the following line in the syslog-ng configuration file:

options {ts_format(iso)};

Resolving the IP addresses of the clients to domain names can decrease the performance of syslog-ng. See Section 7.4, “Using name resolution in syslog-ng” for details.