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Prometheus Haskell Client

A simple and modern, type safe, idiomatic Haskell client for Prometheus monitoring. Specifically there is no use of unsafe IO or manual ByteString construction from lists of bytes. Batteries-included web server. Version 0.* supports Prometheus v1.0 and version 2.* supports Prometheus v2.0.

Usage Example

{-# LANGUAGE OverloadedStrings #-}

module Example where

import           Control.Monad.IO.Class                         (liftIO)
import           System.Metrics.Prometheus.Concurrent.Http      (serveHttpTextMetricsT)
import           System.Metrics.Prometheus.Concurrent.RegistryT
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

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

Advanced Usage

A Registry and StateT-based RegistryT are available for unit testing or generating lists of [IO a] actions that can be sequenced and returned from pure code to be applied.


  • Implement help docstrings.
  • Implement GHC-specific metrics.
  • Implement summary metric.
  • Encode name and labels on register.
  • Implement ReaderT for Concurrent Registry.
  • Library documentation and example.
  • Name and label validation