Can I monitor custom metrics? Are there plugins?

Yes - collectd supports an enormous variety of plugins.

We have documented a number of them which you can find on the collectd plugins page.

Additionally, you can submit any custom metric you like via our Metrics HTTP API.

On Windows platforms, the BBWin agent also supports plugins, known as externals. Unfortunately the available documentation is currently very limited! We hope to help improve this situation over the coming months.