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Configurable bucket for latency metric #69

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Jul 7, 2024
Merged

Configurable bucket for latency metric #69

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29 changes: 25 additions & 4 deletions wai-middleware-prometheus/src/Network/Wai/Middleware/Prometheus.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@ module Network.Wai.Middleware.Prometheus
, Default.def
, instrumentHandlerValue
, instrumentHandlerValueWithFilter
, instrumentHandlerValueWithHistogramAndFilter
, ignoreRawResponses
, instrumentApp
, instrumentIO
Expand Down Expand Up @@ -80,7 +81,16 @@ instrumentHandlerValueWithFilter ::
-> (Wai.Request -> Text) -- ^ The function used to derive the "handler" value in Prometheus
-> Wai.Application -- ^ The app to instrument
-> Wai.Application -- ^ The instrumented app
instrumentHandlerValueWithFilter resFilter f app req respond = do
instrumentHandlerValueWithFilter =
instrumentHandlerValueWithHistogramAndFilter requestLatency

instrumentHandlerValueWithHistogramAndFilter ::
Prom.Vector Prom.Label3 Prom.Histogram
-> (Wai.Response -> Maybe Wai.Response) -- ^ Response filter
-> (Wai.Request -> Text) -- ^ The function used to derive the "handler" value in Prometheus
-> Wai.Application -- ^ The app to instrument
-> Wai.Application -- ^ The instrumented app
instrumentHandlerValueWithHistogramAndFilter histogram resFilter f app req respond = do
start <- getTime Monotonic
app req $ \res -> do
case resFilter res of
Expand All @@ -89,7 +99,7 @@ instrumentHandlerValueWithFilter resFilter f app req respond = do
end <- getTime Monotonic
let method = Just $ decodeUtf8 (Wai.requestMethod req)
let status = Just $ T.pack (show (HTTP.statusCode (Wai.responseStatus res')))
observeSeconds (f req) method status start end
observeSecondsWithHistogram histogram (f req) method status start end
respond res

-- | 'Wai.ResponseRaw' values have two parts: an action that can be executed to construct a
Expand Down Expand Up @@ -149,10 +159,21 @@ observeSeconds :: Text -- ^ handler label
-> TimeSpec -- ^ start time
-> TimeSpec -- ^ end time
-> IO ()
observeSeconds handler method status start end = do
observeSeconds = do
observeSecondsWithHistogram requestLatency

-- | Record an event to the middleware metric.
observeSecondsWithHistogram :: Prom.Vector Prom.Label3 Prom.Histogram
-> Text -- ^ handler label
-> Maybe Text -- ^ method
-> Maybe Text -- ^ status
-> TimeSpec -- ^ start time
-> TimeSpec -- ^ end time
-> IO ()
observeSecondsWithHistogram histograms handler method status start end = do
let latency :: Double
latency = fromRational $ toRational (toNanoSecs (end `diffTimeSpec` start) % 1000000000)
Prom.withLabel requestLatency
Prom.withLabel histograms
(handler, fromMaybe "" method, fromMaybe "" status)
(flip Prom.observe latency)

Expand Down