Re: [Haskell-cafe] sendfile leaking descriptors on Linux?

As far as I can tell, stepcut was probably correct in his diagnosis before. I was getting two processes started because of a stray cron job. 2010/2/26 Thomas Hartman :

Indeed, the error occurs when two processes are running at the same time. One process isn't serving anything, and the other is just looping, reported that it can't stop because the port is taken, and repeating ad infinitum.

The loop I have is

ulimit -v 150000 while true; do  echo starting patchtag: `date` ./dist/build/patchtagserver/patchtagserver --port=80 --  echo patchtag exited: `date`  echo patchtag exited: `date` >> patch-tag.log  rm -f _local/patchtagserver_state.lock

The ulimit is so that it will die after consuming a reasonable amount of memory. (I seem to have a memory leak somewhere, but it takes many hours to get up to 150M.)

Everything else looks pretty standard to me. It seems to work as designed most of the time, but occasionally will result in two processes. I'm baffled as to how this happens.

If anybody has any idea, I would love to hear them.

2010/2/26 Jeremy Shaw :

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Hello, It will be interesting to see if that makes any difference -- it shouldn't. In happstack-server we use 'listenOn'. According to the documentation listenOn already sets ReuseAddr: http://hackage.haskell.org/packages/archive/network/2.2.1.7/doc/html/Network... A quick look at the source code confirms it is calling:    setSocketOption sock ReuseAddr 1 It sounds to be like you are getting the socket in use error because you have 2 processes running. Seems like the first one hasn't really died, but the second one is started anyway. How is it that your loop starts a second server when the first one has not finished? - jeremy On Fri, Feb 26, 2010 at 1:43 PM, Thomas Hartman wrote:

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Thanks, I altered my top level request handler as follows

mysmartserver conf h stateProxy = do      socket <- bindPort conf

           

     webserverTid <- forkIO $ simpleHTTPWithSocket socket conf h      putStrLn . ( "starting happs server" ++ ) =<< time

     control <- startSystemState stateProxy -- start the HAppS state system      putStrLn . ( "happs state started" ++ ) =<< time

     waitForTermination      killThread webserverTid      stateShutdown control

I can't replicate the error reliably so I won't know if it actually fixed the problem for a while, therefore just leaving this cookie crumb trail in case others may find it helpful.

2010/2/26 Brandon S. Allbery KF8NH :

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On Feb 26, 2010, at 04:28 , Thomas Hartman wrote:

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me: Like mightybyte, I run my app in a shell loop that will just restart it after a crash. But every once in a while it won't restart because of the busy socket and I need to do a manual restart, killing multiple processes (usually 2).

the error I get is:

bind: resource busy (Address already in use)

This is on application restart?  It's not out of file descriptors, it's just the system keeping the socket around (netstat will show it in TIME_WAIT, or possibly in a shutdown negotiation state such as LAST_ACK, FIN_WAIT, etc.  TCP lacks *reliable* socket shutdown negotiation).

You want to configure the socket with SO_REUSEADDR before trying to bind it (setSocketOption socket ReuseAddr 1).

As to the portable version of sendfile, it's because not all systems offer a sendfile() system call.  Linux and *BSD do, and can use the native implementation; the portable version emulates sendfile() when it doesn't exist, at the price of additional CPU usage/system load (sendfile() having been created specifically to reduce system load in the common case for web servers).

-- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery@kf8nh.com system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu electrical and computer engineering, carnegie mellon university    KF8NH