fix(sut): the unit for service time was wrong.

src/sut/dumblog/src/Dumblog/Journal/Worker.hs

@@ -34,9 +34,7 @@ timeIt metrics action = do
   result <- action
   !endTime <- getCurrentTime
   Metrics.measure metrics ServiceTime
-    -- `diffUTCTime` has a precision of 10^-12 s, so after multiplying with 10^9
-    -- we get milliseconds.
-    (realToFrac (diffUTCTime endTime startTime * 1e9))
+    (realToFrac (diffUTCTime endTime startTime * 1e6)) -- µs.
   return result
 
 wakeUpFrontend :: Blocker (Either Response Response) -> Int -> Either Response Response

src/sut/dumblog/src/Dumblog/Metrics/Main.hs

@@ -5,6 +5,7 @@ module Dumblog.Metrics.Main where
 import Control.Monad (forever)
 import Control.Concurrent (threadDelay)
 import Text.Printf (printf)
+import GHC.IO.Encoding (setLocaleEncoding, utf8)
 
 import Dumblog.Journal.Metrics
 import Journal.Internal.Metrics
@@ -13,6 +14,7 @@ import Journal.Internal.Metrics
 
 metricsMain :: IO ()
 metricsMain = forever $ do
+  setLocaleEncoding utf8 -- Otherwise we can't print µ...
   metrics <- newMetrics dumblogSchema "/tmp/dumblog.metrics"
   putStrLn ansiClearScreen
   mMin  <- percentile metrics ServiceTime 0
@@ -23,13 +25,13 @@ metricsMain = forever $ do
   m9999 <- percentile metrics ServiceTime 99.99
   mMax  <- percentile metrics ServiceTime 100
   putStrLn "Service time:"
-  putStrLn (maybe "N/A" (printf "  min   %10.2f ms") mMin)
-  putStrLn (maybe "N/A" (printf "  med   %10.2f ms") mMed)
-  putStrLn (maybe "N/A" (printf "  90    %10.2f ms") m90)
-  putStrLn (maybe "N/A" (printf "  99    %10.2f ms") m99)
-  putStrLn (maybe "N/A" (printf "  99.9  %10.2f ms") m999)
-  putStrLn (maybe "N/A" (printf "  99.99 %10.2f ms") m9999)
-  putStrLn (maybe "N/A" (printf "  max   %10.2f ms") mMax)
+  putStrLn (maybe "N/A" (printf "  min   %10.2f µs") mMin)
+  putStrLn (maybe "N/A" (printf "  med   %10.2f µs") mMed)
+  putStrLn (maybe "N/A" (printf "  90    %10.2f µs") m90)
+  putStrLn (maybe "N/A" (printf "  99    %10.2f µs") m99)
+  putStrLn (maybe "N/A" (printf "  99.9  %10.2f µs") m999)
+  putStrLn (maybe "N/A" (printf "  99.99 %10.2f µs") m9999)
+  putStrLn (maybe "N/A" (printf "  max   %10.2f µs") mMax)
   cnt <- count metrics ServiceTime
   putStrLn (printf "  count %10d" cnt)
   threadDelay 1_000_000