Hardware and performance

 
 
Picture of Thomas Haynes
Requested Range Not Satisfiable
 

"Requested Range Not Satisfiable

None of the range-specifier values in the Range request-header field overlap the current extent of the selected resource."

Anyone ever seen this error before?

The server started giving this fault about 1 in 5 attempts to load random pages. Refreshing the page would make it load at about the same ration. At the same time, IE refused to open pdf documents on about half the student computers. In every case Firefox worked.

I have never seen anything like this before and am stumped.

Regards...   Tom


 
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Picture of Thomas Haynes
Re: Requested Range Not Satisfiable
 

"At the same time, IE refused to open pdf documents on about half the student computers. In every case Firefox worked."

Anyone have a clue on this?

I can link to a pdf file in Moodle, and it will open in Firefox but gives me an error about a corrupt file in IE 

 
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Picture of Frances Bell
Re: Requested Range Not Satisfiable
 
Doesn't Adobe need you to have the reader installed on the client machine? So maybe the student machines with IE as browser also have an earlier version of Adobe Acrobat Reader than the ones with Firefox. I suppose that if you are publishing Adobe Acrobat files, then you should include a link to the download of the latest version of Adobe Acrobat reader (or make sure it is installed if students are using in labs).
I also wondered about visually impaired students - might they not have a problem with Adobe Acrobat.? This is something that I wonder about with resources that we provide.
 
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Picture of Thomas Haynes
Re: Requested Range Not Satisfiable
 
All the students have the same image on the laptops. They all have Acrobat Reader 6.

The very same student with the same laptop and the same Acrobat Reader install will have the page give a "corrupted file" on the pdf with IE and then Firefox will open it.

I am pretty puzzled.

I have looked through the logs for a hint, but either I am looking for the wrong thing or there is nothing there.

 
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Picture of Frances Bell
Re: Requested Range Not Satisfiable
 
Hope that someone else can solve your mystery.  I am just feeling pretty smug that I moved to Firefox last week smile

 
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Picture of Mark Stevens
Re: Requested Range Not Satisfiable
Group Moodle Course Creator Certificate holders
It looks like Firefox is your solution.  Spend your time installing Firefox and developing things for learning rather than wasting time on IE big grin

Sincerely,
Mark
 
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Picture of Thomas Haynes
Re: Requested Range Not Satisfiable
 
I am all over the Firefox solution, and I have no problem just telling my students that they need to install Firefox to use Moodle.

The crisis for me here is that we are about to roll out a "course" for Faculty and Staff. It goes live next Wed. with a planned demo from me in the Faculty/Staff meeting.

This new course is supposed to be the place to manage all the announcements, fliers from HR, special schedules, etc. I've got the staff creating pdfs to preserve formatting on calendars and fliers. We can't get them to open in IE. Until we get this figured out, they have stopped.

The project is dead in the water if we can't use Moodle with IE. Our attendance program requires IE, and it can't be tricked. The majority of faculty/staff could not tell you what browser they are running, and if they have to switch browsers, they simply won't use the course.

I am somewhat anxious for a solution.
 
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Picture of Michael Penney
Re: Requested Range Not Satisfiable
Group Developers

That is NOT a solution if you want Moodle to be used widely.

Most Universities and schools just don't go around changing lab computers at whim, it often takes months, and then you have the issue of other things that don't work as well in IE.

And your tech support staff will quickly be overwhelmed trying to explain what is going on to thousands of students and teachers, why they suddenly have to install new software, how to do it, etc.

The easier solution will be to dump Moodle for an LMS that runs on what is still the most common browser.

It would be the same situation for us anyway if Moodle suddenly stopped working properly on Netscape, as about 20% of our faculty and students use Netscape. If we had to start telling 1400 people that had to switch to IE to use the LMS, we wouldn't want to use the LMS, either (in fact Blackboard's buggy behavior on NS is a big reason some of our folks want to use Moodle--but only because Moodle works(ed?) so well on both, no one wants to have to spend time explaining technical issues to their students while they are trying to teach biology, history, etc.

 
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Picture of Wayne Gaish
Re: Requested Range Not Satisfiable
 

Hi -  have you tried the obvious - check the apache logs to see if there are any clues there. We use different browsers depending of the faculty ie we have Macs and PCs. We have not had any problems with pdf.

I agree that it may be an IE setting or just IE

I did find the following web article http://www.shahine.com/omar/CommentView,guid,e707e1a5-5873-4d8b-88f8-8b56fb9d15b2.aspx

it might help.

long live firefox !

regards

Wayne

 
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Picture of Thomas Haynes
Re: Requested Range Not Satisfiable
 
The problem has been "fixed" by setting cache to 0.

This behavior is some combination of IE 6 updates and Adobe updates, but essentially Moodle has to "just work" or faculty members simply won't use it.

Logs were no help, and I scoured them for clues...
 
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Picture of Michael Penney
Re: Requested Range Not Satisfiable
Group Developers

Hi Thomas, was this with 1.4.1 or 1.4.2?

There were some changes made to the caching settings in 1.4.2 that seem to be playing havoc with IE.

 
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Picture of Thomas Haynes
Re: Requested Range Not Satisfiable
 
Michael...

I am using 1.4.2

Thanks...   Tom
 
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Picture of Petr Škoda
Re: Requested Range Not Satisfiable
Group DevelopersGroup Documentation writersGroup Moodle HQGroup Particularly helpful Moodlers
Isn't it the same problem as described here? What is the configuration of your server?

skodak
 
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Picture of Thomas Haynes
Re: Requested Range Not Satisfiable
 
The server is runing WBEL, a version of RHEL 3 that has been recompiled from source.

It has all the stock stuff. PHP 4.3.2., Apache 2.0

I have been using the Zend Optimizer.

I don't think the problems are the same. Mine is not related to Word, and it is browser specific. My students can't download the zip files either.

I am willing to upgrade PHP if there is a compelling reason, but I am using WBEL for the stable "enterprise" environment in our school setting. There have been no problems with the other AMP applications on this machine. I can't make a change like that casually.
 
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Picture of Petr Škoda
Re: Requested Range Not Satisfiable
Group DevelopersGroup Documentation writersGroup Moodle HQGroup Particularly helpful Moodlers
I think it is not Moodle issue, I would try to upgrade both Apache and PHP.

But if you have weblib.php version 1.282.2.18 or later, the problem could be revealed by new (problematic - soon to be fixed) caching.

skodak
 
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Martin Langhoff - Sailing
Re: Requested Range Not Satisfiable
Group DevelopersGroup Particularly helpful Moodlers
IE/Acrobat are trying to fetch a file by chunk-by-chunk, using the ranges extension in HTTP 1.1. Usually Acrobat will do this, but should be smart enough to fallback on more widely implemented HTTP headers if it doesn't work.

It is commonly seen where
- IE+embedded Acrobat ActiveX or standalone acrobat is used
- the PDF file is dynamically generated or served by a script

It may be a case of updating Acrobat (and possibly IE). I see setting caching to 0 has helped.

Questions:
- Are you seeing this issue with anything other than PDFs?
- Are you using any proxy? Brand/make/model?
- Do you see the same problem after updating Acrobat?

Moodle "could do" byte-serving for these silly applications, but most people consider it a misfeature of HTTP 1.1. If there's enough interest...

For reference, a few related links:

A great summary of byteserving and why it's a bad idea
http://akosut.com/log/2004/03/14/byte-ranges-considered-harmful

How Acrobat is using it
http://acroeng.adobe.com/BrowserTestSuite/bserve/byteserving.html

Plenty of discussion on php acrobat and range-request. All seems to point to an old MSIE/Acrobat.
http://www.google.com/search?hl=en&lr=&q=acrobat+range-request+php&btnG=Search

It isn't trivial to do in PHP
http://www.tug.org/pipermail/pdftex/2003-June/003398.html
 
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Picture of Petr Škoda
Re: Requested Range Not Satisfiable
Group DevelopersGroup Documentation writersGroup Moodle HQGroup Particularly helpful Moodlers
If I understand it correctly we should send:
Accept-Ranges: none
in all headers, right?


http://www.freesoft.org/CIE/RFC/2068/160.htm
 
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Martin Langhoff - Sailing
Re: Requested Range Not Satisfiable
Group DevelopersGroup Particularly helpful Moodlers
Hmmm. Server MAY send it and client MAY know what to do with it, I love internet standards. So precise in the amount of uncertainly they leave for us to resolve.

We should give it a shot ;)
 
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Picture of Petr Škoda
Re: Requested Range Not Satisfiable
Group DevelopersGroup Documentation writersGroup Moodle HQGroup Particularly helpful Moodlers
I will update my latest patch here tonight. I will add Accept-ranges to all headers too.

I hope people wil test it, so that we can get it in CVS soon wink

skodak
 
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Picture of Thomas Haynes
Re: Requested Range Not Satisfiable
 
"It may be a case of updating Acrobat (and possibly IE). I see setting caching to 0 has helped.

Questions:
- Are you seeing this issue with anything other than PDFs?
- Are you using any proxy? Brand/make/model?
- Do you see the same problem after updating Acrobat?"

We have seen this with zip files as well. It is present with IE and not with Firefox as before. The problem has been there with varying degrees of updates. The Adobe on mine was updated as part of the troubleshooting process, and it had the problem before and after.

Currently the proxy/filter machine is an appliance

http://www.k12usa.com/secureapp.asp

which works quite well. The moodle server is on the internal network, and the problems occur both inside and outside.

As close as I can tell, changing the cache to 0 completely "cured" the problem. The symptoms went away as far as my users could tell, and we are back to normal. Zip files and pdfs both are working.

The 228 faculty/staff members have been imported, and the faculty "course" goes live Wed.
 
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Picture of Thomas Haynes
Re: Requested Range Not Satisfiable
 
Help...

IE is up to its tricks again.

pdfs give a corrupted file error in IE. They work fine in Firefox.

All I have done over break is update the machine via yum. This included the php rpm. I am using WBEL, and these are the same rpm as RHEL but rebuilt.

I have parallel installations of 1.4.2 and 1.4.3+. I get the error with the filelifetime  set to zero or not on both.

I really want this to work and would appreciate any help.


 
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Picture of Thomas Haynes
Re: Requested Range Not Satisfiable
 
FWIW, I downgraded my various php rpms, went back to the old optimizer php.ini, and cleared the cache on my IE.

The files now open as they are supposed to.

I have no clue, but I seem to have gotten it functional for the teachers/students who come back tomorrow.

Ultimately, I will need to have this working with a more secure version of php, but I will be able to set up another install and experiment now.
 
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Picture of Petr Škoda
Re: Requested Range Not Satisfiable
Group DevelopersGroup Documentation writersGroup Moodle HQGroup Particularly helpful Moodlers
The cleaning of cache in IE could be a solution.

You can also try change Acrobat preferences
  • launch Acrobat Reader
  • go to menu File/Preferences
  • choose Internet
  • disable "Allow fast web view" and "Allow speculative downloading in the background"

skodak
 
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Picture of Petr Škoda
Re: Requested Range Not Satisfiable
Group DevelopersGroup Documentation writersGroup Moodle HQGroup Particularly helpful Moodlers
I did found some interesting information about PDF and byte-serving:

My conclusion:
  1. Acrobat Reader is buggy - Fast web view may not always work
  2. PDF generators do not fully support linearization - only some files may be problematic
  3. Apache (or other server) may not respond to byte-request headers properly - PHP script is not called at all (??) (probably your case; why? because there is no PHP code that throws Requested range not..., IMO the server must be doing it!)

IMHO if Apache sends request to PHP script for byte range and the script replyes with complete file, it should be OK according to specification (am I right??).

For your specific problem I suppose the cause might be Apache and the solution could be to disable Fast web view in Acrobat Reader (or to upgrade Apache & PHP to latest version).

Anyway I think that it would be possible to conduct some test and find the exact answer, but I would need access to your server and one free day to work on this problem sad

skodak

PS: to Martin
Do we want byte-serving for PDF in Moodle file.php (== incremental loading, AKA Fast web view)??
I think I would be able to use code from the script referenced above to do it smile

Edit:
The problem could be in some weird proxy that does not ask server and immediately replyes with error. That could be a reason to remove Accept-Ranges: none from all headers....
 
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Picture of Thomas Haynes
Re: Requested Range Not Satisfiable
 
Petr...

I really appreciate the responses.

I made a move last year from RH 7.3 to WBEL 3 (a recompiled RHEL 3). It is stable, and has a pretty good set of default packages. I have two production machines and a developmental box. I may install Debian Sarge on the developmental machine, and get a more current package set. I figure I can set up a parallel install and see how it works.

We have a large userbase here, and changing settings in Adobe isn't going to be much good. I can check it on my laptop, but I need to have the same install as the rest of the faculty/students or I won't catch problems after upgrades.

Thanks...   Tom
 
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