Starting with syslog-ng OSE 3.2, syslog-ng became plugin based, which has some consequences that even experienced syslog-ng users may stumble into.
The most obvious one, is that syslog-ng now produces a series of .so files loaded at runtime, instead of being a monolithic executable. If a given .so is not not or not loaded, some of the functionality may be missing. This usually manifests itself by a syntax error when parsing the configuration file.
Second: if you compile syslog-ng from source, the unit/functional test programs also want to load plugins, and they try to do that from the install directory. This means that you first have to install syslog-ng using "make install" before running the testsuite. This is not an ideal solution, but should work for now.
Plugins are loaded from $prefix/lib/syslog-ng by default, however this can be changed using the `module-path` global, which contains the list of directories where syslog-ng should look for modules. You can change this using the syntax:
@define module-path `module-path`:/usr/local/lib/syslog-ng-plugins
I think that's it for now.