Example.hs

{-# LANGUAGE OverloadedStrings #-}

module Main where

import Control.Monad.IO.Class (liftIO)
import System.Metrics.Prometheus.Concurrent.RegistryT
import System.Metrics.Prometheus.Http.Scrape (serveMetricsT)
import System.Metrics.Prometheus.Metric.Counter (inc)
import System.Metrics.Prometheus.MetricId


main :: IO ()
main = runRegistryT $ do
    -- Labels can be defined as lists or added to an empty label set
    connectSuccessGauge <- registerGauge "example_connections" (fromList [("login", "success")])
    connectFailureGauge <- registerGauge "example_connections" (addLabel "login" "failure" mempty)
    connectCounter <- registerCounter "example_connection_total" mempty
    latencyHistogram <- registerHistogram "example_round_trip_latency_ms" mempty [10, 20 .. 100]

    liftIO $ inc connectCounter -- increment a counter

    -- [...] pass metric handles to the rest of the app

    serveMetricsT 8080 ["metrics"] -- http://localhost:8080/metric server