RE: I'm willing to improve handling of HTTP redirects in Sampler and Proxy.

["Stover, Michael" <Mi...@usa.xerox.com>]

Jordi,
     This sounds very sensible on the whole.  I have two comments:
1.  Please check out CVS anonymously, and base your changes off the code
under the "src_1" directory.  That is the current code.

2.  The reason JMeter prevented multiple redirects is because of some sites
that created an infinite loop otherwise.  I'm sure this was ultimately a
problem in JMeter, so if you can fix it properly, we'd all be much obliged.

Also, it might be easiest if you just concentrate on HTTPSampler and fixing
it's code, and I can plug in the GUI controls to allow a user to turn
redirect on and off.  I'll leave that up to you.

-Mike

> -----Original Message-----
> From: Jordi Salvat i Alabart [mailto:jsalvata@atg.com]
> Sent: Sunday, June 16, 2002 6:43 PM
> To: jmeter-dev@jakarta.apache.org
> Subject: I'm willing to improve handling of HTTP redirects in Sampler
> and Proxy.
> 
> 
> Hi.
> 
> This is my first message to this list, so please bear with me if I'm 
> breaking any rules/customs.
> 
> I'm re-reading this message before sending it and noticed its 
> much too 
> long, so here's a summary:
> 
> - I'm working towards adding a "follow redirects" 
> configuration flag to 
> the HTTP Samplers, so as to allow correcting the way the HTTP Proxy 
> Server handles redirects. I will also make an effort to 
> correct related 
> comments.
> 
> - I'd like to confirm noone else is working in the same direction(s).
> 
> - I would appreciate someone who knows the code better than I 
> to have a 
> look at my description of the issue (below) and warn me if I've 
> seriouldy misunderstood the code and any traps for the unwary she's 
> aware of.
> 
> End of summary. Here's the full story:
> 
> I've been having trouble with the handling of HTTP redirects 
> (302 return 
> codes with a Location: header) by the HTTP Proxy Server. You can 
> reproduce my problem simply by using the proxy and pointing 
> at any page 
> which redirects to a page in a different directory (for example, try 
> http://bugs.debian.org/).
> 
> The problem occurs because the proxy is following these client-side 
> redirects by itself, and so the client never learns the redirect has 
> happened and the base URL has changed (much as in "server-side" 
> redirects). As a consequence, all relative URLs in the resulting page 
> will be wrong.
> 
> To solve this, I would need the Proxy Server to handle 
> redirects back to 
> the client as any other HTTP proxy (or at least as any other 
> I've seen 
> so far).
> 
> But then the proxy server would add both URLs (the original and the 
> redirected one) to the test case, which then, when run, would 
> cause the 
> page to be requested twice. One quick solution to this would 
> be not to 
> record the first URL, but this would change the nature of the 
> test. The 
> right(TM) solution is to be able to record URLs in such a way that 
> redirects won't be followed.
> 
> I've been reviewing the HTTPSampler code and I've found the 
> comments and 
> code related to the handling of redirects quite strange. It seems to 
> have gone through some changes over time which have made it pretty 
> confusing. To start with, comments describe the "redirected" 
> parameter 
> as "whether redirection is turned on", but it rather seems to mean 
> "whether we're processing a redirect", and seems to be used used to 
> avoid following more than one level of redirection.
> 
> I've tested a two-level redirect (page1->page2->page3) and the proxy 
> does the redirect from page1 to page2, but then handles the 
> second 302 
> response  to the client, which does the redirect to page3. 
> The URLs of 
> page1 and page3 get recorded, but not that for page2. I 
> consider this a bug.
> 
> Is there a reason I can't think of to avoid multi-level redirects?
> 
> Is there a reason I can't think of to have the proxy do the 
> redirections 
> instead of the client?
> 
> To solve all of this, I'm adding a "follow redirects" boolean 
> property 
> to the HTTP Sampler(s) (of course the default will be "true" so as to 
> stay compatible with the old behaviour). Do you think this is 
> a sensible 
> working direction? Is anyone already working in this direction?
> 
> In the process, I'm doing my best to correct the comments, and I will 
> also remove that multi-level redirect limitation (unless 
> someone tells 
> me I shouldn't).
> 
> Next step will be to have the HTTP Proxy use HTTP Samplers with 
> followRedirects turned off. I think this will solve the problems I'm 
> having while recording. Again: Is this sensible? Is anyone working in 
> this same direction?
> 
> I'll submit my changes once I've tested them. This should 
> hopefully be 
> sometime next week.
> 
> Of couse, being novice to this code, I will appreciate any 
> hints/directions/suggestions you may have.
> 
> Salut,
> 
> Jordi.
> 
> 
> 
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