[Haskell-cafe] sendfile leaking descriptors on Linux?

[Jeremy Shaw]

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.html#v%3AlistenOn

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 <tphyahoo at gmail.com> wrote:

> Thanks, I altered my top level request handler as follows
>
> mysmartserver conf h stateProxy = do
>      socket <- bindPort conf
>
>       <I added (setSocketOption socket ReuseAddr 1) here>
>       <Should this be added in a comment, or even in function code,
> in Happstack.Server.SimpleHTTP? What are the tradeoffs, when would you
> *not* want ot use ReuseAddr?)
>
>      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 <allbery at ece.cmu.edu>:
> > On Feb 26, 2010, at 04:28 , Thomas Hartman wrote:
> >>
> >> 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 at kf8nh.com
> > system administrator [openafs,heimdal,too many hats] allbery at ece.cmu.edu
> > electrical and computer engineering, carnegie mellon university    KF8NH
> >
> >
> >
>
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