Bazsi's Home Automation blog

Last time I've written about how syslog-ng is able to change message contents. I thought it'd be useful to give you a more practical example, instead of a generic description. It is quite common to convert SNMP traps to syslog messages. The easiest implementation is to run snmptrapd and have it create a log message based on the trap. There's a small issue though: snmptrapd uses the UNIX syslog() API, and as such it is not able to propagate the originating host of the SNMP trap to the hostname portion of the syslog message. This means that all traps are logged as messages coming from the host running snmptrapd, and the hostname information is part of the message payload. Of course it'd be much easier to process syslog messages, if this were not the case. A solution would be to patch snmptrapd to send complete syslog frames, but that would require changing snmptrapd source. The alternative is to use the new parse and rewrite features of syslog-ng 3.0. First, you need to f...

For a long time I meant to give the "log statistics" feature of syslog-ng an overhaul, and finally with the advent of syslog-ng 3.0, this was done. I'm not sure all of you know, but even earlier syslog-ng versions (2.1 and 2.0) did collect some per-source and per-destination statistics. These were reported periodically in the system log. The problem with this approach that it didn't really scale: with a large configuration the statistics message could become kilobytes long, and parsing this information from a file possibly several gigabytes in size is daunting. syslog-ng 3.0 has two important changes in this area: it adds several new kinds of counters (like per-host counters), and a UNIX domain socket where you can query the current status of these counters. As counters certainly have an overhead, you can now control how much statistics you want to gather. The new stats_level() option has three levels for now: stats_level(0) is basically the same as earlier syslog-ng ...