RRDTool, and C# .NET bindings

RRDTool is pretty much ubiquitous in Linux/Unix cluster environments – or at least, it is in those I’ve worked with. It provides simple but highly reliable round-robin database services into which you can dump pretty much any metric you like. It’ll keep a running dataset at the granularity and duration you define; enable you to export data in chart and xml form; and even perform some useful analysis.

These days I’m typically working in Windows environment, and typically most clients I work for need some sort of dashboard to aggregate information about their clusters and grids. For a long time RRDTool was a pain to build on Windows, and there was no single .NET wrapper. The front runner – NHawk – actually spawned rrdtool processes rather than wrapping the underlying libs direct.

Now it turns out that someone’s contributed .NET bindings to the trunk of RRDTool. I figured I’d see if I could get it working, on 64bit Win7 (although actually x86 is fine for my app), under Visual Studio 2010.

I checked trunk out from SVN and took a look.

The first thing is to set up the dependencies – I tried to take a short cut and begin with a GTK+ package, but found it’s best to start with the files mentioned explicitly in the WIN32_BUILD_TIPS file.

There were a few apparently non-serious build errors in the rrdlib project. In several places explicit casts from void* were required on malloc, realloc. Also, there was some skipping of variable initialization in switch statements – latter can be fixed just by enclosing in a block.

Running through the tutorial with rrdtutorial raised one problem – an error claiming “No positional legend found”. The error was generated in rrd_graph_helper.c. The log showed that this was a work in progress, so I updated to the preceding version, built and it worked apparently fine.

After that I built the .NET bindings – basically fine, although I wrangled everything to x86 in the end just to get started. But then – nothing was being exported. There’s a .def file in the lib solution, but it doesn’t appear to exist any more. So: I wrapped a copy of the public method declarations in #ifdef WIN32, and prefixed with __declspec(dllexport), then rebuilt the .NET binding solution and: success.

All looks good to go. Next step is to grab metrics from windows performance counters in a C# app and see what I can present through RRDTool.