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From Ryan Frishberg <rfris...@andrew.cmu.edu>
Subject [users@httpd] Slow Responding to Extra Request on Persistent Connection
Date Thu, 03 May 2007 23:25:46 GMT
Hey, I'm writing a program to test the performance of apache (we had a
similar problem with lighttpd), and I keep running into a problem with
persistent connections.  We make a single request, like:

GET fileName HTTP/1.1
Host: server:80
Keep-Alive: 300
Connection: keep-alive

And we get a response back.  We then make another, similar request on
the same connection, and we get a response back, but there's a huge
delay in-between sending our request and getting the response for the
second request.

To give you an idea of the times:

request 1: sent at 0 ms, received at 1 ms
request 2: sent at 1 ms, received at 41 ms
request 3: sent at 41 ms, received at 81 ms
request 4: sent at 81 ms, received at 121 ms

And we see this 40 ms delay all throughout after the first request. 
Clearly it
doesn't take that long to deliver the file, so we're not sure what 
gives...why the
delay?  Just FYI, we're testing on a high-bandwidth, low-latency network.

Also, we do HTTP pipelining, and when we send all these requests at once
on one connection, we get the response back extremely quick--we're just
not sure why the 40 ms or so delay between requests on the same
persistent connection and not on the pipelined connection.  There's
almost no lag between the machine, so we're not sure what's up.

Is this something apache and lighttpd do to make sure people don't 
request too much.
  Is this a setting we can change?

Thanks,
Ryan

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