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The default value + -- is ["metrics"] which corresponds to the path /metrics. + , prometheusInstrumentApp :: Bool + -- ^ Whether the default instrumentation should be applied to the + -- application. If this is set to false the application can still be + -- instrumented using the 'instrumentApp' function. The default value is + -- True. + , prometheusInstrumentPrometheus :: Bool + -- ^ Whether the default instrumentation should be applied to the + -- middleware that serves the metrics endpoint. The default value is + -- True. + } + +instance Default.Default PrometheusSettings where + def = PrometheusSettings { + prometheusEndPoint = ["metrics"] + , prometheusInstrumentApp = True + , prometheusInstrumentPrometheus = True + } + +{-# NOINLINE requestLatency #-} +requestLatency :: Prom.Metric (Prom.Vector Prom.Label1 Prom.Summary) +requestLatency = Prom.unsafeRegisterIO $ Prom.vector "handler" + $ Prom.summary info Prom.defaultQuantiles + where info = Prom.Info "http_request_duration_microseconds" + "The HTTP request latencies in microseconds." + +-- | Instrument a WAI app with the default WAI metrics. +-- +-- If you use this function you will likely want to override the default value +-- of 'prometheusInstrumentApp' to be false so that your app does not get double +-- instrumented. +instrumentApp :: String -- ^ The label used to identify this app + -> Wai.Application -- ^ The app to instrument + -> Wai.Application -- ^ The instrumented app +instrumentApp handler app req respond = + observeMicroSeconds handler (app req respond) + +-- | Instrument an IO action with timing metrics. This function can be used if +-- you would like to get more fine grained metrics, for instance this can be +-- used to instrument individual end points. +-- +-- If you use this function you will likely want to override the default value +-- of 'prometheusInstrumentApp' to be false so that your app does not get double +-- instrumented. +instrumentIO :: String -- ^ The label used to identify this IO operation + -> IO a -- ^ The IO action to instrument + -> IO a -- ^ The instrumented app +instrumentIO = observeMicroSeconds + +observeMicroSeconds :: String -> IO a -> IO a +observeMicroSeconds handler io = do + start <- getCurrentTime + result <- io + end <- getCurrentTime + let latency = fromRational $ toRational (end `diffUTCTime` start) * 1000000 + Prom.withLabel handler (Prom.observe latency) requestLatency + return result + +-- | Expose Prometheus metrics and instrument an application with some basic +-- metrics (e.g. request latency). +prometheus :: PrometheusSettings -> Wai.Middleware +prometheus PrometheusSettings{..} app req respond = + if Wai.requestMethod req == HTTP.methodGet + && Wai.pathInfo req == prometheusEndPoint + then measure measureMetrics "prometheus" $ respondWithMetrics respond + else measure measureApp "app" $ app req respond + where + measureMetrics = prometheusInstrumentPrometheus + measureApp = prometheusInstrumentApp + measure shouldInstrument handler io + | shouldInstrument = observeMicroSeconds handler io + | otherwise = io + +respondWithMetrics :: (Wai.Response -> IO Wai.ResponseReceived) + -> IO Wai.ResponseReceived +respondWithMetrics respond = do + metrics <- Prom.exportMetricsAsText + respond $ Wai.responseBuilder HTTP.status200 headers $ BS.byteString metrics + where + headers = [(HTTP.hContentType, "text/plain; version=0.0.4")] diff --git a/tests/doctest.hs b/tests/doctest.hs new file mode 100644 --- /dev/null +++ b/tests/doctest.hs @@ -0,0 +1,9 @@ +module Main where + +import Test.DocTest + +main :: IO () +main = doctest [ + "-isrc" + , "Network.Wai.Middleware.Prometheus" + ] diff --git a/wai-middleware-prometheus.cabal b/wai-middleware-prometheus.cabal new file mode 100644 --- /dev/null +++ b/wai-middleware-prometheus.cabal @@ -0,0 +1,46 @@ +name: wai-middleware-prometheus +version: 0.1.0.0 +synopsis: + WAI middlware for exposing http://prometheus.io metrics. +description: + WAI middlware for exposing http://prometheus.io metrics. +homepage: https://github.com/fimad/prometheus-haskell +license: Apache-2.0 +license-file: LICENSE +author: Will Coster +maintainer: willcoster@gmail.com +copyright: 2015 Will Coster +category: Network +build-type: Simple +cabal-version: >=1.10 + +source-repository head + type: git + location: https://github.com/fimad/prometheus-haskell + +library + hs-source-dirs: src/ + default-language: Haskell2010 + exposed-modules: + Network.Wai.Middleware.Prometheus + build-depends: + base >=4.6 && <4.8 + , bytestring >=0.9 + , data-default + , http-types + , prometheus-client + , text >=0.11 + , time + , wai >=3.0 + ghc-options: -Wall + +test-suite doctest + type: exitcode-stdio-1.0 + default-language: Haskell2010 + hs-source-dirs: tests + ghc-options: -Wall + main-is: doctest.hs + build-depends: + base + , doctest + , prometheus-client