Mystery of the Plodding HTTP Requests

by Scot Hacker


For a while now, I've been observing a strange phenomenon here at the j-school: Some of our computers respond extremely slowly to our own web site. Take two machines sitting side by side on the exact same 100 megabit network. Both machines are configured identically in terms of subnet, gateway, and DNS addresses. Both have static IPs. Now I try to access the jschool homepage. One browser will have the homepage loaded faster than you can blink. But on the machine next to it, the browser's status bar will say "Sending request..." for 4-5 seconds, then the page will come in all of a sudden. No other web sites are affected - only our own site, our intranet, and our development server. The affected machines can access external web sites lickety split, but they bog down completely when accessing sites on our own subnet.




The problem affects about half of our Macs, but does not affect any of our Windows machines. It does not seem to matter whether the Macs are running OS 9 or OS X. The problem is not CPU/memory related - we're talking G4s with 512MBs. Up until a few days ago, my Mac was fortunately unaffected by the problem. But after loading Jaguar onto it (I have a legit copy), my PowerMac, which is my main work machine, is now affected by the problem as well. As webmaster, I reload pages constantly - you can imagine how aggravating this is.




At first I suspected this was a DNS issue, and tried using a variety of alternate DNS servers the university makes available. No difference. Next I decided to bypass DNS by loading the NetInfo database with custom host data. No difference - the problem persists. In fact, the problem persists even when accessing the site by its IP address. Ping times and FTP responses are very fast - it's just HTTP request times that lag inexplicably. Browser used is irrelevant - I get the same molasses-like behavior with IE, Mozilla, and OmniWeb on this machine.




I'm baffled and frustrated and running out of time to spend on this problem. Is there anything in our Apache configuration that could cause behavior like this? Other theories?




Update: As an experiment, I tried shutting down Apache and starting up OmniHTTPD in it's place for a few minutes. The problem seemed to vanish! This indicates an Apache configuration problem. All optimizations in httpd.conf are at their default values. But what kinds of optimizations could affect Macs but not PCs, and only some Macs at that?





Clues appreciated!


6 Comments

bensite85
2002-08-15 13:55:18
Browser?
What browser and version are you using?


I noticed something very similar with www.oreillynet.com. With most versions of IE, the banner ad at the top loads (and sometimes the top nav) very quickly and then 3-4 seconds later the rest of the page appears.


With Mozilla and Opera, the whole page loads at once and quickly.


Perhaps using the same browser, but different versions have different approaches to rendering? Not sure though.

amayil
2002-08-15 14:01:47
Elimiate the browser
Telnet to port 80 and 'GET /' on your webserver for both the name and the ip and see if there is any difference on both machines.
shack
2002-08-15 15:34:00
Elimiate the browser
I get the same behavior with this technique - on the "slow" machine, the GET response takes several seconds, but it's instantaneous from the "fast" machine.
acroyear
2002-08-16 09:46:56
Browser?
That could just be an I.E. optimization. Browsers in the old days (netscape 1-4) didn't like to do the layout of the page until all the data was loaded, especially when tables are involved (as they are in 90% of all web sites out there). If a single image took its time loading (particularly an advert from doubleclick or a slashdotted site), then nothing would appear for minutes at a time.


To look more responsive, I.E. would, on occasion, go ahead and layout what it had received so far.


With faster machines, and with the incredible optimizations in Gecko, doing the layout is not nearly the browser-freezer it used to be, so Mozilla and other new browsers will constantly be redoing their layout as things show up, looking constantly responsive to both user and data.


IE probably doesn't do continuous updates the way Gecko based browsers do, but does a layout update ever 2 seconds or so -- more responsive than Netscape 4, but less so than Mozilla.


As for Mac vs. Windows, keep in mind the Mac browser shares almost no I.E. code with the windows version.


Joe

shack
2002-08-16 11:25:59
Browser?
This definitely isn't a browser layout issue - the "slow" machines can render all other sites lickety split - just not our own. Our layout is extremely simple. There's something else going on...
eric5
2004-02-24 06:31:16
Did you ever figure this out?
Help! We are having THE SAME PROBLEM. Your jschool site loads fast now on Mac IE. What was the fix?