Prometheus Haskell Client

A simple and modern, type safe, performance focused, 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.

A key design element of this library is that the RegistryT monad transformer is only required for registering new time series. Once the time series is registered, new data samples may just be added in the IO monad.

Note: Version 0.* supports Prometheus v1.0 and version 2.* supports Prometheus v2.0.

• Hackage Package
• Github Repo

Usage Example

{-# LANGUAGE OverloadedStrings #-}

module Example where

import           Control.Monad.IO.Class                         (liftIO)
import           System.Metrics.Prometheus.Http.Scrape          (serveMetricsT)
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

    serveMetricsT 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.

Tasks

• 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