This is a bit of an ugly first pass. The code needs some cleanup and there are some open questions, but it works and has docs and tests. Fixes #136.

This attaches to the process’s beforeExit event (supported in Node.js, Deno, and Bun) when auto-flushing is enabled in order to automatically flush when a program exits. Before, you needed to remember to call metrics.flush() manually at the end of your program, which is easy to forget (or not even know about in the first place!).

It also adds a close() method (not sure about the name) that flushes and buffered metrics and disables auto-flushing. It does not prevent adding new metrics to the buffer, but maybe it should? (Would they error? Get dropped silently? Call the onError handler?)

To-do/open questions:

• Clean up implementation. At the very least, get some of this code out of the BufferedMetricsLogger constructor.
• Dedupe all the mock reporter code in tests.
• Is close() a good name? Other ideas: (Update: renamed to stop)
  • stop()
  • shutdown()
  • destroy()
  • disable()
  • pause()
• Should close() also prevent buffering new metrics? (i.e. make addPoint() a no-op, or maybe throw an exception or call the global error handler) (Update: decided no for now.)