properly format stats log numbers: no e-notation

src/Hash2Pub/PostService.hs

@@ -35,6 +35,7 @@ import qualified Network.HTTP.Types        as HTTPT
 import           System.Random
 import           Text.Read                 (readEither)
 
+import           Formatting                (float, format, (%), fixed)
 import qualified Network.Wai.Handler.Warp  as Warp
 import           Servant
 import           Servant.Client
@@ -113,7 +114,10 @@ instance DHT d => Service PostService d where
             port' = fromIntegral (confServicePort conf)
             warpSettings = Warp.setPort port' . Warp.setHost (fromString . confServiceHost $ conf) $ Warp.defaultSettings
         -- log a start message, this also truncates existing files
-        TxtI.writeFile (confLogfilePath conf) "# Starting mock relay implementation\n"
+        TxtI.writeFile (confLogfilePath conf) $ Txt.unlines
+            [ "# Starting mock relay implementation\n"
+            , "#relay receive rate   ;relay delivery rate   ;instance publish rate ;instance fetch rate"
+            ]
         -- Run 'concurrently_' from another thread to be able to return the
         -- 'PostService'.
         -- Terminating that parent thread will make all child threads terminate as well.
@@ -813,12 +817,11 @@ evaluateStatsThread serv statsAcc = getPOSIXTime >>= loop
           -- format: total relayReceiveRates;total relayDeliveryRates;postFetchRate;postPublishRate
           -- later: current (reported) load, target load
           TxtI.appendFile (confLogfilePath . serviceConf $ serv) $
-              Txt.intercalate ";" (Txt.pack <$> (
-              [ show . sum . relayReceiveRates
-              , show . sum . relayDeliveryRates
-              , show . postPublishRate
-              , show . postFetchRate
-              ] <*> pure rateStats)) <> "\n"
+              format ((fixed 20) % ";" % (fixed 20) % ";" % (fixed 20) % ";" % (fixed 20) % "\n")
+                  (sum . relayReceiveRates $ rateStats)
+                  (sum . relayDeliveryRates $ rateStats)
+                  (postPublishRate rateStats)
+                  (postFetchRate rateStats)
           loop now