A rsyslog string generator is what I had previously called a "template module" - in essence a facility to generate a template string with some custom native C code. I have decided to name it a bit differently, because at some later stage there may be other uses for these types of modules as well. Specifically, I am thinking about adding custom name-value pairs to the message object, and then a string generator (or strgen for short) could be used to generate such a value as well.
Implementation went smooth. I implemented both the interface as well as a small set of important core strgens, those that are frequently used to write files or forward message to remote machines. I did not touch any others, as that is probably not really necessary -- and could easily be done any time if need arises.
The new interface also provides a capability to third-parties that enables them to create their own high speed parsers. The performance impact can be dramatic, just think about cases where multiple regular expression calls can be replaced by a single call and some C logic.
Finally, these modules may even provide a way to fund rsyslog development. Adiscon can probably sell them for some small amount (I guess around $500 based on what needs to be done, in some cases maybe less, in some maybe a bit more). I guess that would be attractive for anyone who needs both high speed and a custom format and runs rsyslog for profit. Getting into all the details to develop such a thing oneself probably costs more than our whole implementation effort. I hope we will get some orders for these, and I hope that folks will contribute the strgen back to the project. Their plus is then that we maintain it for free and the plus for the community is that, in the long term, we will hopefully get a large directory of ready-to use custom strgens (OK, that sidesteps the funding process a bit, but... ;)).
I have also managed to write some basic doc on the new capability, to be seen here:
The code has been merged into v5-devel (the master branch) and will most probably be released early next week. Then, it will undergo the usual devel/beta cycle, so that availability in a stable v5 release can be expected towards the end of summer 2010. Special thanks go to David Lang, who provided good advise that helped me create the new functionality.