metrics_reader
=====
[](https://hex.pm/packages/metrics_reader)
An application that exposes Folsom metrics in common standardised formats.
This is important for several reasons:
- Applications provide a common interface for the same purpose
- Exposing application metrics in standardised formats allows existing tools
to scrape these metrics e.g. Prometheus
- Knowledge is transferable when the same problem is solved in a consistent
manner.
The metrics reader exposes the application metrics via an rpc call to the
nodetool:
```
./bin/metrics_reader metrics
```
## The metrics reader server
Metrics should be registered with the metrics reader server if they are to be
reported via the console:
metrics_reader:register(subscriber_acks).
It is also possible to de-register a registered metric:
metrics_reader:deregister(subscriber_acks).
Finally, in order to examine the registered metrics:
metrics_reader:metrics().
## The metrics observer server
For scalar metrics, it is possible to periodically snapshot the values and
record the resulting values in a histogram. This allows richer statistics to be
derived from simple scalar values. Be aware that observing a metric will cause
the server to clear the metric's current value every time it is sampled.
In order to observe a metric, it is necessary to provide a name for the
histogram that will be created:
metrics_observer:observe(subscriber_acks, subscriber_acks_per_second).
It is also possible to unobserve a metric:
metrics_observer:unobserve(subscriber_acks).
## Configuration
{format, prometheus_format} # defaults to prometheus exposition format
{histogram_acc_interval_sec, 10} # defaults to 1 second
{histogram_slide_interval_sec, 60} # defaults to 60 second
## Export formats
An `export_format` behaviour is defined that consists of the following callbacks:
callback histogram(Name :: binary(), Histogram :: #{}) ->
[binary()].
An default `prometheus_format` formatter is already provided that will convert
the metric values to the prometheus textual exposition format.
## Build
```bash
$ rebar3 compile
```
In order to run tests...{to do}
## Release
```
$ rebar3 release
```
