Add git revision to Prometheus metrics

cabal.project.freeze

@@ -190,6 +190,7 @@ constraints: any.Cabal ==3.14.1.0,
              any.ghc-platform ==0.1.0.0,
              any.ghc-prim ==0.12.0,
              any.ghci ==9.10.3,
+             any.gitrev ==1.3.1,
              any.gridtables ==0.1.1.0,
              any.haddock-library ==1.11.0,
              any.half ==0.3.3,

flora.cabal

@@ -191,6 +191,7 @@ library
     effectful-plugin,
     envparse,
     filepath,
+    gitrev,
     heptapod ^>=1.1.0.0,
     hsec-core,
     http-api-data,

src/core/Flora/Environment/Env.hs

@@ -37,6 +37,7 @@ data FloraEnv = FloraEnv
 
 data AppMetrics = AppMetrics
   { packageImportCounter :: P.Vector P.Label1 P.Counter
+  , gitRevision :: P.Vector P.Label1 P.Gauge
   }
 
 data BlobStoreImpl = BlobStoreFS FilePath | BlobStorePure

src/core/Flora/Monitoring.hs

@@ -1,13 +1,17 @@
+{-# LANGUAGE TemplateHaskell #-}
+
 module Flora.Monitoring
   ( increaseCounter
   , increasePackageImportCounter
   , registerMetrics
   , increaseCounterBy
   , increasePackageImportCounterBy
+  , setGitHash
   ) where
 
 import Control.Monad (replicateM_)
 import Data.Text
+import Development.GitRev (gitHash)
 import Effectful
 import Effectful.Prometheus
 import Prometheus
@@ -24,8 +28,22 @@ registerMetrics = do
               { metricName = "flora_imported_packages_total"
               , metricHelp = "Packages imported and their index"
               }
+  let gitHashMetric =
+        P.vector "git_revision" $
+          P.gauge
+            P.Info
+              { metricName = "git_revision"
+              , metricHelp = "Git revision"
+              }
   packageImportCounter <- P.register packageImportCount
-  pure $ AppMetrics packageImportCounter
+  gitHashText <- P.register gitHashMetric
+  pure $ AppMetrics packageImportCounter gitHashText
+
+setGitHash
+  :: Metrics AppMetrics :> es
+  => Eff es ()
+setGitHash =
+  setLabelledGauge gitRevision $(gitHash) 1.0
 
 increaseCounterBy
   :: Metrics AppMetrics :> es

src/web/FloraWeb/Server.hs

@@ -79,6 +79,7 @@ import Flora.Environment.Env
 import Flora.Logging qualified as Logging
 import Flora.Model.BlobStore.API
 import Flora.Monad
+import Flora.Monitoring (setGitHash)
 import Flora.Tracing qualified as Tracing
 import FloraJobs.Runner
 import FloraJobs.Types (JobsRunnerEnv (..))
@@ -125,11 +126,13 @@ runFlora = do
             liftIO $ do
               forM_ env.mltp.eventlogSocket Socket.start
               when (isJust env.mltp.eventlogSocket) (blueMessage "🔥 Sending live events to socket")
-            liftIO $ when env.mltp.prometheusEnabled $ do
-              blueMessage $ "🔥 Exposing Prometheus metrics at " <> baseURL <> "/metrics"
-              void $ P.register P.ghcMetrics
-              when (System.os == "linux") $ void $ P.register P.procMetrics
-              void $ P.register (P.counter (P.Info "flora_imported_packages_total" "The number of imported packages"))
+            when env.mltp.prometheusEnabled $ do
+              liftIO $ blueMessage $ "🔥 Exposing Prometheus metrics at " <> baseURL <> "/metrics"
+              runPrometheusMetrics env.metrics $ do
+                void $ P.register P.ghcMetrics
+                when (System.os == "linux") $ void $ P.register P.procMetrics
+                setGitHash
+
             liftIO $ when env.mltp.zipkinEnabled (blueMessage "🖊️ Connecting to Zipkin endpoint")
             liftIO $ when (env.environment == Development) (blueMessage "🔁 Live reloading enabled")
             let withLogger = Logging.makeLogger env.mltp.logger