fix(admin): log admin server exceptions and close admin socket

Admin server was crashing silently and requests hang indefinitely.
With this fix, we are now logging the admin server exceptions and also
close the socket afterwards so admin request don't hang.

Signed-off-by: Taimoor Zaeem <taimoorzaeem@gmail.com>

src/PostgREST/Admin.hs

@@ -11,7 +11,8 @@ import Control.Monad.Extra       (whenJust)
 import Network.Socket            hiding (addrFamily)
 import Network.Socket.ByteString
 
-import PostgREST.AppState    (AppState)
+import PostgREST.AppState    (AppState, getConfig)
+import PostgREST.Config      (AppConfig (..))
 import PostgREST.MediaType   (MediaType (..), toContentType)
 import PostgREST.Metrics     (metricsToText)
 import PostgREST.Network     (resolveSocketToAddress)
@@ -24,13 +25,22 @@ import           Protolude
 
 runAdmin :: AppState -> Maybe NS.Socket -> NS.Socket -> Warp.Settings -> IO ()
 runAdmin appState maybeAdminSocket socketREST settings = do
+  conf <- getConfig appState
   whenJust maybeAdminSocket $ \adminSocket -> do
     address <- resolveSocketToAddress adminSocket
-    observer $ AdminStartObs address
-    void . forkIO $ Warp.runSettingsSocket settings adminSocket adminApp
+    void . forkIO $ handle (onError adminSocket) $
+      Warp.runSettingsSocket (adminServerSettings conf address) adminSocket adminApp
   where
     adminApp = admin appState socketREST
     observer = AppState.getObserver appState
+    adminServerSettings config addr =
+      settings
+        & Warp.setBeforeMainLoop (observer $ AdminStartObs addr)
+        & maybe identity Warp.setPort (configAdminServerPort config)
+
+    onError adminSock ex = do
+      observer $ AdminServerCrashedObs ex
+      NS.close adminSock -- we close the socket so request doesn't hang
 
 -- | PostgREST admin application
 admin :: AppState.AppState -> NS.Socket -> Wai.Application