Thread killed by timeout manager

[chrisdone]

With this file

stack runhaskell wrp.hs --resolver lts-18.0

{-# LANGUAGE TypeFamilies, QuasiQuotes, MultiParamTypeClasses,
             TemplateHaskell, OverloadedStrings #-}
import           Control.Concurrent
import qualified Text.Blaze.Html5 as H
import qualified Data.Text as T
import           Data.Text (Text)
import           Control.Monad
import           Yesod
import           Yesod.WebSockets
data Piggies = Piggies
instance Yesod Piggies
mkYesod "Piggies" [parseRoutes|
  / HomeR GET
|]
getHomeR :: Handler Html
getHomeR = do webSockets (forever (do liftIO (threadDelay (1000 * 1000))
                                      sendTextData ("Bump!" :: Text)))
              pure (H.script "// Create WebSocket connection.\n\
                             \const socket = new WebSocket('ws://localhost:3035');\n\
                             \\n\
                             \// Connection opened\n\
                             \socket.addEventListener('open', function (event) {\n\
                             \    socket.send('Hello Server!');\n\
                             \});\n\
                             \\n\
                             \// Listen for messages\n\
                             \socket.addEventListener('message', function (event) {\n\
                             \    console.log('Message from server ', event.data); socket.close()\n\
                             \});")
main = warpDebug 3035 Piggies

I see this output

$ stack runhaskell wrp.hs --resolver lts-18.0

wrp.hs:30:8: warning: [-Wdeprecations]
    In the use of ‘warpDebug’
    (imported from Yesod, but defined in Yesod.Core.Dispatch):
    Deprecated: "Please use warp instead"
   |
30 | main = warpDebug 3035 Piggies
   |        ^^^^^^^^^
18/Jun/2021:17:38:23 +0100 [Info#yesod-core] Application launched @(yesod-core-1.6.20.1-Jp7zmLxTY8gEM32OuxAOUR:Yesod.Core.Dispatch src/Yesod/Core/Dispatch.hs:175:11)
  C-c C-c

 $ stack runhaskell wrp.hs --resolver lts-18.0

wrp.hs:30:8: warning: [-Wdeprecations]
    In the use of ‘warpDebug’
    (imported from Yesod, but defined in Yesod.Core.Dispatch):
    Deprecated: "Please use warp instead"
   |
30 | main = warpDebug 3035 Piggies
   |        ^^^^^^^^^
18/Jun/2021:17:35:13 +0100 [Info#yesod-core] Application launched @(yesod-core-1.6.20.1-Jp7zmLxTY8gEM32OuxAOUR:Yesod.Core.Dispatch src/Yesod/Core/Dispatch.hs:175:11)
127.0.0.1 - - [18/Jun/2021:17:35:17 +0100] "GET / HTTP/1.1" 200 362 "" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/79.0.3945.130 Safari/537.36"
127.0.0.1 - - [18/Jun/2021:17:35:17 +0100] "GET / HTTP/1.1" 500 - "" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/79.0.3945.130 Safari/537.36"
  C-c C-cwrp.hs: Thread killed by timeout manager
ghc: Thread killed by timeout manager

The two "Thread killed by timeout manager" messages appear when I hit C-c C-c. But I've elsewhere seen the message appear without shutting down the server. This is the best repro I can make so far.

Is this expected behavior? It seems to be one message for the websocket thread and one for the handler. If I omit the webSockets call, there is only one.