[syslog-ng] setting sequenceId in forwarded log messages read from journald reader

Wed Jul 29 07:54:38 UTC 2020

Hello Peter,
 I do not know a way to read sequence id without modifying the journal module. (Syslog-ng already do it to persist it's current position in journal. So it is definitely feasible to read it.)

 I found this documentation about cursors: https://www.freedesktop.org/software/systemd/man/sd_journal_get_cursor.html, and I am worried about this part of the documentation:
  "The cursor string should be considered opaque and not be parsed by clients."

 So parsing and using the sequence id as a core functionality will be unwise. However I can imagine a feature behind a configuration option (turned off by default), where syslog-ng will put the whole __CURSOR string into the NVTable, so it can be accessed via a custom parser.

 Please tell me your opinion about this solution. (Especially: is there a particular reason why you don't want to modify the journal module?)

Best regards,
Laci

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From: syslog-ng <syslog-ng-bounces at lists.balabit.hu> on behalf of Peter Vollmer <peter.vollmer at gmail.com>
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Subject: [syslog-ng] setting sequenceId in forwarded log messages read from journald reader

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Hi,
I am currently trying to find a way to set meta.sequenceId of log messages that have been read from the locally running systemd-journal to forward them to a remote syslog server that expects the logs to contain a sequenceId according to  RFC 5424 section 7.3.1.

I found that a sequence number could be taken from the  __CURSOR field "i=..." of the journald log:

# journalctl -o json-pretty -f
...
 "__CURSOR" : "s=02a7b30ba17b4a43846f265706bd3a70;i=f01;b=ba633698f20848e480bca4e72476e4d3;m=1a355c1d5;t=5ab670340c8ea;x=33389988ef680e7e",
...
My problem is that the journal reader does not seem to parse the __CURSOR string when reading from journald logs. Is there a way to get this information into meta.sequenceId of the forwarded log without modifying the systemd-journal module in syslog-ng ?

Thank you for any ideas and best regards

Peter Vollmer
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