[plt-scheme] Re: web-server: connection timeout with open file handles

From: Dave Gurnell (d.j.gurnell at gmail.com)
Date: Wed Apr 22 10:07:11 EDT 2009

My initial diagnosis on this may have been wrong.

I've added a line to instruct the web server to increase the  
connection timeout every so often.
I get complete file downloads now, but file handles are still being  
left open.

-- Dave

> Hi all,
> I'm having a couple of issues with timeouts in the web server. This  
> is kind of related to the "dynamic-wind & kill-thread" thread.
> I'm using a servlet and make-response/incremental to serve files  
> from the file system to web users. I've attached simplified test  
> code below (tested on PLT
> Three problems:
>   - large file downloads can take a long time, and can be killed by  
> the web server's connection timeout (default 60 seconds);
>   - when the connection times out, the servlet thread is killed and  
> leaves the file handle open permanently ("lsof -p <PID>").
>   - over time, the web server accrues open file handles until it  
> hits the OS-imposed limit ("ulimit -n")  and stops working properly  
> (connecting to Postgres in my case).
> I remember back in the day we had the same problem with files served  
> using dispatch-files.ss. The solution there was to insert a call to  
> adjust-connection-timeout! to increase the connection timeout for  
> large files.
> Here it's not so simple because make-response/incremental can do  
> more than just serve static files.
> I'd like to be able to call adjust-connection-timeout! from servlet  
> code, but I don't think that feature is available from inside a  
> servlet (no access to the connection object).
> Cheers,
> -- Dave

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