cardano-tracer: added restart test case

cardano-tracer/cardano-tracer.cabal

@@ -440,6 +440,30 @@ test-suite cardano-tracer-test-ext
                         -rtsopts
                         -with-rtsopts=-N
 
+test-suite cardano-tracer-restart
+  import:               project-config
+  type:                 exitcode-stdio-1.0
+
+  -- we expect unixy paths
+  if os(windows)
+    buildable:          False
+
+  hs-source-dirs:       test/restart-test
+  main-is:              restart-test.hs
+
+  build-tool-depends:   cardano-tracer:cardano-tracer
+                      , cardano-tracer:demo-forwarder
+
+  -- keep this minimal: what the script actually uses
+  build-depends:        base
+                      , directory
+                      , filepath
+                      , process
+
+  ghc-options:          -threaded
+                        -rtsopts
+                        -with-rtsopts=-N
+
 benchmark cardano-tracer-bench
   import:               project-config
   type:                 exitcode-stdio-1.0

cardano-tracer/test/restart-test/restart-config.yaml

@@ -0,0 +1,8 @@
+networkMagic: 42
+network:
+  tag: AcceptAt
+  contents: "sock"
+logging:
+- logRoot: "/tmp/cardano-tracer-restart-test-logs"
+  logMode: FileMode
+  logFormat: ForMachine

cardano-tracer/test/restart-test/restart-test.hs

@@ -0,0 +1,138 @@
+{-# LANGUAGE ScopedTypeVariables #-}
+
+module Main where
+
+import           Control.Concurrent (threadDelay)
+import           Control.Exception (IOException, catch, finally)
+import           Control.Monad (unless, void, when)
+import           System.Directory (doesFileExist, getCurrentDirectory, listDirectory,
+                   removePathForcibly)
+import           System.Exit (exitFailure)
+import           System.FilePath (takeDirectory, (</>))
+import           System.IO (hPutStrLn, stderr)
+import           System.Process (CreateProcess (..), ProcessHandle, StdStream (..), createProcess,
+                   proc, terminateProcess, waitForProcess)
+
+main :: IO ()
+main = do
+  let dir      = "/tmp/cardano-tracer-restart-test-logs"
+      sock     = "sock"
+      logLink  = dir </> (sock ++ "@0") </> "node.json"
+      waitSecs = 5
+
+  cfg <- resolveConfigPath
+
+  -- Fresh start.
+  catchIgnore (removePathForcibly dir)
+
+  -- Run demo-forwarder
+  forwarderH <- startProc "demo-forwarder" [sock, "Initiator"]
+
+  let cleanup = catchIgnore (removePathForcibly dir)
+
+  -- Ensure the forwarder is killed and logs cleaned at the very end
+  finally
+    (do
+      -- Start first cardano-tracer
+      tracer1H <- startProc "cardano-tracer" ["--config", cfg]
+
+      finally
+        (do
+          sleepSeconds waitSecs
+          ensureNonEmpty logLink
+            "Nothing has been written to the file with trace messages"
+
+          -- Kill first tracer
+          terminateProcess tracer1H
+          void (waitForProcess tracer1H)
+
+          sleepSeconds 2
+
+          -- Start second tracer
+          tracer2H <- startProc "cardano-tracer" ["--config", cfg]
+
+          finally
+            (do
+              sleepSeconds waitSecs
+              ensureNonEmpty logLink
+                "Nothing has been written to the file since the restart of cardano-tracer"
+
+              let logDir = dir </> (sock ++ "@0")
+              entries <- listDirectory logDir
+              let candidates = filter (not . isSpecialEntry) entries
+              let count = length candidates
+              when (count /= 2) $ do
+                hPutStrLn stderr $
+                  "Two log files are expected to be present, found: " ++ show count
+                exitFailure)
+            (safeTerminate tracer2H))
+        (safeTerminate tracer1H))
+    (do
+        safeTerminate forwarderH
+        cleanup)
+
+--------------------------------------------------------------------------------
+-- Helpers
+
+startProc :: FilePath -> [String] -> IO ProcessHandle
+startProc cmd args = do
+  (_, _, _, ph) <- createProcess (proc cmd args)
+                    { std_in  = Inherit
+                    , std_out = Inherit
+                    , std_err = Inherit
+                    }
+  pure ph
+
+sleepSeconds :: Int -> IO ()
+sleepSeconds s = threadDelay (s * 1000000)
+
+ensureNonEmpty :: FilePath -> String -> IO ()
+ensureNonEmpty fp errMsg = do
+  exists <- doesFileExist fp
+  unless exists $ failWith errMsg
+  sz <- getFileSize fp
+  when (sz == 0) $ failWith errMsg
+  where
+    failWith msg = hPutStrLn stderr msg >> exitFailure
+
+getFileSize :: FilePath -> IO Integer
+getFileSize fp = do
+  contents <- readFile fp
+  pure (toInteger (length contents))
+
+safeTerminate :: ProcessHandle -> IO ()
+safeTerminate ph = terminateProcess ph >> void (waitForProcess ph)
+
+catchIgnore :: IO () -> IO ()
+catchIgnore act = act `catch` \(_ :: IOException) -> pure ()
+
+isDot :: FilePath -> Bool
+isDot "."  = True
+isDot ".." = True
+isDot _    = False
+
+isCurrentLog :: FilePath -> Bool
+isCurrentLog "node.json" = True
+isCurrentLog _           = False
+
+isSpecialEntry :: FilePath -> Bool
+isSpecialEntry fp = isDot fp || isCurrentLog fp
+
+resolveConfigPath :: IO FilePath
+resolveConfigPath = go =<< getCurrentDirectory
+  where
+    configRelative root =
+      root </> "cardano-tracer" </> "test" </> "restart-test" </> "restart-config.yaml"
+
+    go dir = do
+      let cfgPath = configRelative dir
+      exists <- doesFileExist cfgPath
+      if exists
+        then pure cfgPath
+        else do
+          let parent = takeDirectory dir
+          if parent == dir
+            then do
+              hPutStrLn stderr "Unable to locate restart-config.yaml"
+              exitFailure
+            else go parent