opossum-prometheus
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Prometheus metrics for opossum circuit breaker
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# Prometheus Metrics for Opossum Circuit Breaker
[](https://coveralls.io/github/nodeshift/opossum-prometheus?branch=main)
[](https://snyk.io/test/npm/opossum-prometheus)
This module provides [Prometheus](https://prometheus.io/) metrics for
[opossum](https://github.com/nodeshift/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](https://github.com/siimon/prom-client) registry.
The metrics about the circuit will be added to the provided registry instead
of the global registry.
The [default metrics](https://github.com/siimon/prom-client#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 |