[ic] Interesting Failure Reading Scratch Variables from Session
John Young
interchange-users@icdevgroup.org
Wed Jul 17 23:14:01 2002
I wrote:
> >Here's a funny one that may already be known, or perhaps some value as an FYI:
> >
> >Newer browsers seem to consistently fail in updating scratch variables
> >stored in a session file when some other delivery failure (in this case a missing
> >image file) occurs; yet Netscape 4.61 does not. Details below for anyone
> >interested. I'm not having a problem with this, because I will insure that
> >I don't have any missing images. It's just a little curious (and I hope that
> >I am coding things properly). I also don't consider this a bug... just a
> >behavior anomaly.
...[quoted details omitted]...
Ed LaFrance replied:
> Unless you are using IC as an http server, which I have heard rumor is
> possible, IC completes all its processing before handing off output to
> Apache, so I don't see how a broken image link could have any bearing on
> IC's correct function. What's more, I have ample first-hand experience with
> a variety of browsers and a wide range of server configurations to back
> this up.
Good point. However, when the complexities of IC, Apache, browsers,
etc. are summed, I believe it is quite possible that a broken image link
could indeed affect IC's function in subtle ways. Such is the nature of
complex, full-featured applications.
What I believe is going here, is that the newer browsers are perhaps
triggering an error signal that the older browser is not, and IC is reacting
differently to the those signals. With additional logDebug's enabled,
I've discovered that broken links coupled with a newer browser generates:
Vend::Server:debug: redo accept on error=Bad file number n=1 v= p= unix= pid=1437 c=11 i=2
yet the older browser, even with broken links, does not.
I've also found that the variable I was trying to save to the session was actually
being saved in the initial session, but IC is switching to another session as soon
as the broken links are encountered ...while using a newer browser.
One can see below that in the first example, with broken links, IC establishes a
new session at line #75. Yet with unbroken links in the following example, one
can see that the original session is continuing to be used at line #77.
Newer browser + broken links:
70 Vend::Session:debug: delete TmpScratch=control_index
71 Vend::Session:debug: delete TmpScratch=control_index
72 Vend::Session:debug: delete TmpScratch=control_index
73 Vend::Session:debug: try to close session id=TuwK26Hu name=TuwK26Hu:192.168.0.4
74 Vend::Session:debug: close session id=TuwK26Hu name=TuwK26Hu:192.168.0.4
> 75 Vend::Session:debug: new session id= name= seed=
76 Vend::Session:debug: open_session: File_sessions=1 Sub=CODE(0x514c8c)
77 Vend::Session:debug: name session user= host=192.168.0.4 (192.168.0.4)
78
79 Vend::Session:debug: name session id=uLG79qXa name=uLG79qXa:192.168.0.4
80
81 Vend::Session:debug: init_session uLG79qXa:192.168.0.4 is: {
82 'values' => {
83 'country' => 'US',
84 'mv_shipmode' => '2DA'
85 },
86 'ohost' => '192.168.0.4',
87 'carts' => {
88 'main' => []
89 },
90 'scratch' => {
Newer browser + unbroken links:
70 Vend::Session:debug: delete TmpScratch=control_index
71 Vend::Session:debug: delete TmpScratch=control_index
72 Vend::Session:debug: delete TmpScratch=control_index
73 Vend::Session:debug: try to close session id=xPIWADWX name=xPIWADWX:192.168.0.4
74 Vend::Session:debug: close session id=xPIWADWX name=xPIWADWX:192.168.0.4
75 Vend::Session:debug: name session user= host=192.168.0.4 (192.168.0.4)
76
> 77 Vend::Session:debug: name session id=xPIWADWX name=xPIWADWX:192.168.0.4
78
79 Vend::Session:debug: session name now xPIWADWX:192.168.0.4
80 Vend::Session:debug: open_session: File_sessions=1 Sub=CODE(0x50d0ac)
81 Vend::Session:debug: read session id=xPIWADWX name=xPIWADWX:192.168.0.4
82
83 Vend::Session:debug: Session:
84 HASH(0x1256214)
85
86 Vend::Session:debug: write session id=xPIWADWX name=xPIWADWX:192.168.0.4
87
88 Vend::Session:debug: delete TmpScratch=page_title
89 Vend::Session:debug: delete TmpScratch=control_index
90 Vend::Session:debug: delete TmpScratch=control_index
Once again, I don't see this as a big problem (after all, we should all keep things
tidy and not have broken links). But I am, however, slightly curious about it from
the standpoint of potential situations where sessions might be switched when one
isn't counting on it (a rare enough possibility as to not be cause for concern).
I suppose this also further supports the validity of testing with multiple browsers.
Christopher F. Miller chimed in:
> Another case of a bug report without sufficient data, eg the code from
> the page in question. Did you weblint the page? Check quoting.
Hmmm... As I mentioned in my original message, I do not consider this a bug at this
point. BTW, weblint does not turn up anything - the page setting the variable is very,
very simple. Perhaps the information above is closer to being sufficient data, and if
not, I have some multi-megabyte icdebug files I'd be happy to email to you off list... ;-)
No, I was initially just hoping that someone more familiar with sessions at a low level
might comment if this stirred something in their mind. If not, no biggy.
BTW, this can easily be tested. Using the following data on your ic server,
retrieve with a newer browser and an older browser if you have it the
following files in this order:
test_putvar.html
test_getvar.html (should show ABC)
test_putvar_noimage.html
test_getvar.html (should fail to show DEF on newer browser because the session switched)
test_putvar.html:
---------------------------------------------------
<html>
<body>
[set whatever]ABC[/set]
<p>
This is a test.
</p>
</body>
</html>
---------------------------------------------------
test_getvar.html:
---------------------------------------------------
<html>
<body>
<p>
This is a test - retrieve the value:
[perl]
$Scratch->{whatever};
[/perl]
</p>
</body>
</html>
---------------------------------------------------
test_putvar_noimage.html:
---------------------------------------------------
<html>
<body>
[set whatever]DEF[/set]
<IMG SRC="/im_not_here.jpg">
<p>
This is a test.
</p>
</body>
</html>
---------------------------------------------------
-John Young