parser module for "last message repeated n times" (pmlastmsg)

Module Name: pmlastmsg

Module Type: parser module

Author: Rainer Gerhards <rgerhards@adiscon.com>

Available Since: 5.5.6

Description:

Some syslogds are known to emit severily malformed messages with content "last message repeated n times". These messages can mess up message reception, as they lead to wrong interpretation with the standard RFC3164 parser. Rather than trying to fix this issue in pmrfc3164, we have created a new parser module specifically for these messages. The reason is that some processing overhead is involved in processing these messages (they must be recognized) and we would not like to place this toll on every user but only on those actually in need of the feature. Note that the performance toll is not large -- but if you expect a very high message rate with tenthousands of messages per second, you will notice a difference.

This module should be loaded first inside rsyslog's parser chain. It processes all those messages that contain a PRI, then none or some spaces and then the exact text (case-insensitive) "last message repeated n times" where n must be an integer. All other messages are left untouched.

Please note: this parser module makes it possible that these messages are properly detected. It does not drop them. If you intend to drop those messages, you need to use the usual filter logic in combination with the discard action. As a side-note, please keep on your mind that the sender discarded messages when the "last message repeated n times" message is emited. You want to consider if that really is what you intend to happen. If not, go change the sender.

Configuration Directives:

There do not currently exist any configuration directives for this module.

Examples:

This example is the typical use case, where some systems emit malformed "repeated msg" messages. Other than that, the default RFC5424 and RFC3164 parsers should be used. Note that when a parser is specified, the default parser chain is removed, so we need to specify all three parsers. We use this together with the default ruleset.

Caveats/Known Bugs:

currently none

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