[Haskell-cafe] sendfile leaking descriptors on Linux?

[Brandon S. Allbery KF8NH]

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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