fix: shutdown should wait for in flight requests

Upgraded warp to 3.4.13 which fixed https://github.com/yesodweb/wai/issues/853
Changed interrupt handling so that instead of killing the main thread, listening sockets are closed which triggers warp graceful shutdown.

src/PostgREST/App.hs

@@ -22,6 +22,7 @@ import GHC.IO.Exception (IOErrorType (..))
 import System.IO.Error  (ioeGetErrorType)
 
 import Control.Monad.Except     (liftEither)
+import Control.Monad.Extra      (whenJust)
 import Data.Either.Combinators  (mapLeft, whenLeft)
 import Data.Maybe               (fromJust)
 import Data.String              (IsString (..))
@@ -79,8 +80,10 @@ run appState = do
 
   AppState.schemaCacheLoader appState -- Loads the initial SchemaCache
   (mainSocket, adminSocket) <- initSockets conf
-
-  Unix.installSignalHandlers observer (AppState.getMainThreadId appState) (AppState.schemaCacheLoader appState) (AppState.readInDbConfig False appState)
+  let closeSockets = do
+        whenJust adminSocket NS.close
+        NS.close mainSocket
+  Unix.installSignalHandlers observer closeSockets (AppState.schemaCacheLoader appState) (AppState.readInDbConfig False appState)
 
   Listener.runListener appState
 

src/PostgREST/Unix.hs

@@ -19,10 +19,9 @@ import           System.Directory      (removeFile)
 import           System.IO.Error       (isDoesNotExistError)
 
 -- | Set signal handlers, only for systems with signals
-installSignalHandlers :: Observation.ObservationHandler -> ThreadId -> IO () -> IO () -> IO ()
+installSignalHandlers :: Observation.ObservationHandler -> IO () -> IO () -> IO () -> IO ()
 #ifndef mingw32_HOST_OS
-installSignalHandlers observer tid usr1 usr2 = do
-  let interrupt = throwTo tid UserInterrupt
+installSignalHandlers observer interrupt usr1 usr2 = do
   install Signals.sigINT  $ observer (Observation.TerminationUnixSignalObs "SIGINT") >> interrupt
   install Signals.sigTERM $ observer (Observation.TerminationUnixSignalObs "SIGTERM") >> interrupt
   install Signals.sigUSR1 usr1