Re: [Haskell-cafe] Amazonka, conduit and sockets not closing

Linux has kernel params you can tweak for socket reuse. Also look up SO_REUSEADDR for background.

On Nov 28, 2020, at 8:44 AM, Bryan Richter wrote:

I thought CLOSE_WAIT *is* one of the "closed" states. TCP sockets stick around for a few minutes after use, right? You may simply be generating sockets faster than one operating system can handle. Find some way to reuse existing sockets, perhaps?

...

On Thu, Nov 26, 2020 at 3:13 PM Magnus Therning wrote:

I've run into a problem with running out of filedescriptors. The following snippet is a trimmed down version of what I'm doing:

#+begin_src haskell main :: IO () main = do awsEnv <- newEnv Discover runAWSCond awsEnv $ sqsSource queueUrl .| C.mapC snd .| sqsDeleteSink queueUrl where runAWSCond awsEnv = runResourceT . runAWS awsEnv . within Frankfurt . C.runConduit

sqsSource :: MonadAWS m => T.Text -> C.ConduitT () (T.Text, T.Text) m () sqsSource queueUrl = do (_, msgs) <- C.lift $ recvSQS queueUrl C.yieldMany msgs sqsSource queueUrl

sqsDeleteSink :: MonadAWS m => T.Text -> C.ConduitT T.Text o m () sqsDeleteSink queueUrl = do C.await >>= \case Nothing -> pure () Just receiptHandle -> do void $ C.lift $ delSQS queueUrl receiptHandle sqsDeleteSink queueUrl

recvSQS queueUrl = do let rm = receiveMessage queueUrl & rmMaxNumberOfMessages ?~ 10 rmrs <- send rm let status = rmrs ^. rmrsResponseStatus msgs = rmrs ^. rmrsMessages & traversed %~ extract pure (status, catMaybes msgs) where extract msg = do body <- msg ^. mBody rh <- msg ^. mReceiptHandle pure (body, rh)

delSQS queueUrl receiptHandle = do let dm = deleteMessage queueUrl receiptHandle send dm #+end_src

This works fine for a while, but given a queue with enough messages it will fail with something like

#+begin_example TransportError (HttpExceptionRequest Request { host = "sqs.eu-central-1.amazonaws.com" port = 443 secure = True requestHeaders = [("Host","sqs.eu-central-1.amazonaws.com"),("X-Amz-Date","20201126T101659Z"),("X-Amz-Content-SHA256","2e4bdf20a857a1416f218b1218670cf019ff53268d0adb34fe06402a62f3271d"),("Content-Type","application/x-www-form-urlencoded; charset=utf-8"),("Authorization","<REDACTED>")] path = "/" queryString = "" method = "POST" proxy = Nothing rawBody = False redirectCount = 0 responseTimeout = ResponseTimeoutMicro 70000000 requestVersion = HTTP/1.1 } (ConnectionFailure Network.Socket.getAddrInfo (called with preferred socket type/protocol: AddrInfo {addrFlags = [AI_ADDRCONFIG], addrFamily = AF_UNSPEC, addrSocketType = Stream, addrProtocol = 0, addrAddress = <assumed to be undefined>, addrCanonName = <assumed to be undefined>}, host name: Just "sqs.eu-central-1.amazonaws.com", service name: Just "443"): does not exist (System error))) #+end_example

After some detours I found out that it's actually not a network issue, but rather that the process runs out of filedescriptors. Using =lsof= I can see that it doesn't seem to close /any/ sockets at all, instead they get stuck in a =CLOSE_WAIT= state:

#+begin_example COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME wd-stats 88674 magnus 23u IPv4 815196 0t0 TCP ip-192-168-0-9.eu-central-1.compute.internal:60624->52.119.188.213:https (CLOSE_WAIT) wd-stats 88674 magnus 24u IPv4 811362 0t0 TCP ip-192-168-0-9.eu-central-1.compute.internal:43482->52.119.189.184:https (CLOSE_WAIT) wd-stats 88674 magnus 25u IPv4 811386 0t0 TCP ip-192-168-0-9.eu-central-1.compute.internal:60628->52.119.188.213:https (CLOSE_WAIT) wd-stats 88674 magnus 26u IPv4 813527 0t0 TCP ip-192-168-0-9.eu-central-1.compute.internal:43486->52.119.189.184:https (CLOSE_WAIT) ... #+end_example

Am I using Amazonka and/or Conduit in a way that results in this? How do I should I use them?

Or, is it an issue somewhere "below" my code? What can I do address that?

Thanks for any insights or help /M

-- Magnus Therning OpenPGP: 0x927912051716CE39 email: magnus@therning.org twitter: magthe http://magnus.therning.org/

Action is the foundational key to all success. — Pablo Picasso _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.

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