Use this documentation with care! It describes
the heavily outdated version 5, which was actively
developed around 2010 and is considered dead by the
rsyslog team for many years now.
This documentation reflects the latest update of the previously existing (now removed) v5-stable branch. It describes the 5.10.2 version, which was never released. As such, it contains some content that does not apply to any released version.
To obtain the doc that properly matches your installed v5 version, obtain the doc set from your distro. Each version of rsyslog contained the version that exactly matches it.
As general advise, it is strongly suggested to upgrade to the current version supported by the rsyslog project. The current version can always be found on the right-hand side info box on the rsyslog web site.
Note that there is no rsyslog community support available for this heavily outdated version. If you need to stick with it, please ask your distribution for support.
Where are the modules integrated into the Message Flow?¶
Depending on their module type, modules may access and/or modify messages at various stages during rsyslog’s processing. Note that only the “core type” (e.g. input, output) but not any type derived from it (message modification module) specifies when a module is called.
The simplified workflow is as follows:
As can be seen, messages are received by input modules, then passed to one or many parser modules, which generate the in-memory representation of the message and may also modify the message itself. The, the internal representation is passed to output modules, which may output a message and (with the interfaces newly introduced in v5) may also modify messageo object content.
String generator modules are not included inside this picture, because they are not a required part of the workflow. If used, they operate “in front of” the output modules, because they are called during template generation.
Note that the actual flow is much more complex and depends a lot on queue and filter settings. This graphic above is a high-level message flow diagram.