Prometheus Metrics for Opossum Circuit Breaker

!Node.js CI

This module provides Prometheus metrics for
opossum circuit breakers. To use
it with your circuit breakers, just pass them in to the PrometheusMetrics
constructor.

For each circuit breaker, the metrics are:

* a prometheus counter for each event name
* a prometheus summary for the events success, failed execution time.

Example:

``js
const CircuitBreaker = require('opossum');
const PrometheusMetrics = require('opossum-prometheus');

// create a couple of circuit breakers
const c1 = new CircuitBreaker(someFunction);
const c2 = new CircuitBreaker(someOtherFunction);

// Provide them to the constructor
const prometheus = new PrometheusMetrics({ circuits: [c1, c2] });

//...
// Provide other circuit breaker later
const c3 = new CircuitBreaker(someOtherFunction3);
prometheus.add([c3]);

// Write metrics to the console
console.log(await prometheus.metrics());
`

This module would typically be used in an application that can provide
an endpoint for the Prometheus server to monitor.

The prometheusRegistry constructor parameter allows you to provide an existing
prom-client registry.
The metrics about the circuit will be added to the provided registry instead
of the global registry.
The default metrics
will not be added to the provided registry.

`js
const CircuitBreaker = require('opossum');
const PrometheusMetrics = require('opossum-prometheus');
const { Registry } = require('prom-client');

// Create a registry
const registry = new Registry();

// create a circuit
const circuit = new CircuitBreaker(functionThatMightFail);
const metrics = new PrometheusMetrics({ circuits: [circuit], registry: registry })
`

Options


The PrometheusMetrics constructor takes an options object as detailed below.

`js
const options = {};
new PrometheusMetrics(options)
`

|Name |Description |Default |
|--------------------------|------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------|
|circuits |A list or individual circuit breaker to create metrics for |No circuits |
|registry |An existing registry to use for prometheus metrics |undefined - The default prometheus registry will be used and default system metrics will be collected|
|exposePerformanceMetrics|Measure the performance of breakers and report them through the registry|true |
|metricPrefix`|Prefix for circuit breakers metrics name|any string |