README.md

Prometheus Metrics for Opossum Circuit Breaker

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:

  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.

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.

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