Prometheus

Bentocache has a built-in plugin for exposing metrics to Prometheus. To use it, you must first install prom-client and @bentocache/plugin-prometheus:

pnpm i prom-client @bentocache/plugin-prometheus

Then, you can use the plugin like so:

import { BentoCache, bentostore } from 'bentocache'
import { prometheusPlugin } from '@bentocache/plugin-prometheus'

const bento = new BentoCache({
  default: 'multitier',
  plugins: [prometheusPlugin()],
  stores: { myCache: bentostore().useL1Layer(memoryDriver()) },
})

Once you have done this, you must expose the metrics endpoint. Let's say you are using Fastify to serve your application. You can expose the metrics endpoint like so:

import { register } from 'prom-client'

fastify.get('/metrics', async (request, reply) => {
  reply.type(register.contentType).send(await register.metrics())
})

And that's it. You can now view your metrics at /metrics and configure Prometheus to scrape them.

Options

prefix

The prefix to use for all metrics. Defaults to bentocache.

registry

The registry to use for all metrics. Defaults to prom-client's default registry.

keyGroups

An array of [RegExp, ((match: RegExpMatchArray) => string) | string] tuples. The first element of the tuple is a regular expression that will be used to match keys. The second element is either a string or a function that will be used to transform the matched key into a new key. This is useful for grouping keys together. For example, if you have a cache that stores users by their ID ( users:1, users:2 ... ) and you want to register metrics for all users together, you can use this option like so:

prometheusPlugin({
  keyGroups: [
    [/^users:(\d+)$/, 'users:*'],
  ]
})

This may be a good practice if you have a lot of keys, because high cardinality can become a problem with Prometheus.

Exposed metrics

Every metric is prefixed with the prefix option (default: bentocache).

graced_hits

Counter. The number of graced values that were returned from the cache.

hits

Counter. The number of cache hits.

misses

Counter. The number of cache misses.

writes

Counter. The number of cache writes.

deletes

Counter. The number of cache deletes.

clears

Counter. The number of cache clears.

bus_messages_published

Counter. The number of messages published to the bus. No labels.

bus_messages_received

Counter. The number of messages received from the bus. No labels.

Grafana dashboard

We have a pretty basic but ready-to-use Grafana dashboard for Bentocache. You can find it here.

Happy to accept any PRs that improve it!