| # couch_stats |
| |
| couch_stats is a simple statistics collection app for Erlang applications. Its |
| core API is a thin wrapper around a stat storage library (currently Folsom,) but |
| abstracting over that library provides several benefits: |
| |
| * All references to stat storage are in one place, so it's easy to swap |
| the module out. |
| |
| * Some common patterns, such as tying a process's lifetime to a counter value, |
| are straightforward to support. |
| |
| * Configuration can be managed in a single place - for example, it's much easier |
| to ensure that all histogram metrics use a 10-second sliding window if those |
| metrics are instantiated/configured centrally. |
| |
| ## Adding a metric |
| |
| 1. Write a stat description file. See `priv/descriptions.cfg for an example. |
| * The metric name should be of type `[atom()]`. |
| * The type should be one of `counter`, `gauge`, or `histogram`. |
| |
| If you don't add your metric to a description file, your metric will be |
| accessible via `couch_stats:sample/1`, but it won't be read by the stats |
| collector and therefore won't be available to HTTP `_stats` requests, etc. |
| |
| 2. Tell couch_stats to use your description file via application configuration. |
| |
| 2. Instrument your code with the helper functions in `couch_stats.erl`. |
