[Xerte-dev] Re: example_zipper issue revisited

Fri May 2 12:58:03 BST 2014

I'm working on a fix for the example_zipper thing - the code can use 
php's tempnam() function instead - which should result in the file being 
cleaned up by PHP afterwards.... or at least not existing in the current 
working directory (i.e. putting it in /tmp or equivalent instead).

David.

On 02/05/14 11:59, Ron Mitchell wrote:
> Hi all
> My inclinations is to scream aaaarrrrrgh! Having had what seems like
> coincidental support requests but is clearly all part of the same issue so
> I've lost track of how long this issue has existed and how widespread it
> might be. To explain...
>
> Late yesterday I received a request from one of the HEA projects regarding
> two of their students being unable to export their projects. After
> investigation it turns out both students have been uploading quite a few
> videos as part of their LO's in this case .flv's and so sure enough the
> projects weren't exporting and creatining more and more example_zipper files
> after each attempt.
>
> One of these particular projects showed 158MB of media via media & quota and
> the other 242MB
> One had 47 zipper files the other 21 and across all the user folders 200+
> zipper files!
>
> I'm a bit concerned how widespread this could be with people unaware of the
> issue. I know it's not best practice to upload loads of video direct but
> lets be realistic users are going to do this and sometimes with good reason.
>
> John - This server was also set to 128MB memory limit by defauls so I tried
> your export.php but that was generating an empty zip download.
>
> I've increased the memory limit to 300MB and with the current 2.1 code and
> original export.php the above two projects export ok without leaving
> example_zipper files behind.
>
> However I also noticed looking at the folder via ftp as you suggested John,
> that if the user cancels the export, even with the memory limit increased,
> the example zipper doesn't then get removed. I don't know if this would be
> different with develop or if your export.php would only work with develop
> John?
>
> But I am wondering if this is a bit of a ticking timebomb for lots of
> installations! If anyone has SSH access to their installation(s) try find .
> -type f -name 'example_zipper*'
>
> Perhaps the temp file name should have been example_zippo! ;-)
>
> We obviously need to crack this one asap...
>
> Ron
>
> -----Original Message-----
> From: xerte-dev-bounces at lists.nottingham.ac.uk
> [mailto:xerte-dev-bounces at lists.nottingham.ac.uk] On Behalf Of Smith, John
> Sent: 01 May 2014 14:51
> To: For Xerte technical developers
> Subject: [Xerte-dev] Re: example_zipper issue revisited
>
> Hi Tom,
>
> Yes, definitely, no worries. I'm about to investigate a windows install with
> both the original code and this new code to see whether I can get it to run.
> Will update you.
>
> Regards,
>
> John Smith | Learning Technologist
> Room A251, Govan Mbeki Building | School of Health & Life Sciences | Glasgow
> Caledonian University Cowcaddens Road | Glasgow | G4 0BA
>
> Please address ALL support requests to hlsblt at gcu.ac.uk where one of the
> School Learning Technologists will pick up the job. This will ensure that
> all jobs are completed as promptly as possible.
> ________________________________________
> From: xerte-dev-bounces at lists.nottingham.ac.uk
> [xerte-dev-bounces at lists.nottingham.ac.uk] On Behalf Of Tom Reijnders
> [reijnders at tor.nl]
> Sent: 01 May 2014 14:46
> To: For Xerte technical developers
> Subject: [Xerte-dev] Re: example_zipper issue revisited
>
> I will look into this, but I don't have much time at the moment. Perhaps
> topnight. Otherwise, it'll have to be next week.
>
> Tom
>
> Smith, John schreef op 1-5-2014 15:38:
>> Well. Preliminary testing looks good with my new code but i haven't tested
> on Windows yet - would be interested in getting Tom's take on all of this...
>>
>> I just added loads of videos via ftp (upload limit set to 7M on this
>> server) and checked the memory limit and it is
>>
>> memory_limit    90M     90M
>>
>> and with each video being used on a page then i've just successfully
> downloaded a 316Mb archive zip without any problems (it took several minutes
> too so the script didn't timeout) and was able to play the videos contained
> within... and this is just a cheap Dreamhost shared server, nothing fancy...
>>
>> On to Windoze...
>>
>> Regards,
>>
>> John Smith | Learning Technologist
>> Room A251, Govan Mbeki Building | School of Health & Life Sciences |
>> Glasgow Caledonian University Cowcaddens Road | Glasgow | G4 0BA
>>
>> Please address ALL support requests to hlsblt at gcu.ac.uk where one of the
> School Learning Technologists will pick up the job. This will ensure that
> all jobs are completed as promptly as possible.
>> ________________________________________
>> From: xerte-dev-bounces at lists.nottingham.ac.uk
>> [xerte-dev-bounces at lists.nottingham.ac.uk] On Behalf Of Ron Mitchell
>> [ronm at mitchellmedia.co.uk]
>> Sent: 01 May 2014 10:58
>> To: 'For Xerte technical developers'
>> Subject: [Xerte-dev] Re: example_zipper issue revisited
>>
>> Hi John
>> the problem is when I originally raised this issue on 8th April it
>> coincided with discovering loads of these un-removed example_zipper
>> files on the sandpit install. At that time I also mentioned the
>> separate session issue as a reason I hadn't updated to a newer
>> revision and I think you mentioned that you thought Tom had fixed this
>> zipper issue in a later revision. So once we'd identified the cause of
>> the session issue (or at least Julian's attempt at fixing his FF issue) I
> updated the sandpit code as well as other servers.
>> Now I've been using the 2.1 branch for this rather than develop so I'm
>> not sure if Tom's fix is in develop but not 2.1 but I think the code
>> is the same at the moment.
>>
>> In short although I've been using a 62MB file from a project a user
>> was unable to export, previously there were loads of these zipper
>> files in loads of different user/project folders and there are
>> probably quite a few again now prior to my changing the memory limit.
>>
>> I could try resetting the memory_limit back on my own server and test
>> again but my previous tests with the 62MB file certainly weren't
>> crashing the server. Let me know if you think its worth testing with
>> larger files and the default 128MB limit or if your and David's later
>> responses have ruled that out as being worthwhile?
>>
>> I know Tom said last night that he was going to revisit his fix for
>> this so would be good to hear back from Tom once he's done that.
>>
>> Cheers
>> Ron
>>
>> -----Original Message-----
>> From: xerte-dev-bounces at lists.nottingham.ac.uk
>> [mailto:xerte-dev-bounces at lists.nottingham.ac.uk] On Behalf Of Smith,
>> John
>> Sent: 01 May 2014 09:57
>> To: For Xerte technical developers
>> Subject: [Xerte-dev] Re: example_zipper issue revisited
>>
>> Hi Ron,
>>
>> Have been thinking about your issue and just wondering whether you
>> might have inadvertently chosen the worst file size possible for the
>> video with 128Mb memory available to PHP. Let me explain (and this is
>> entirely hypothetical)...
>>
>> The zipper creates a blank object (<0.1Mb memory used) The library
>> loads all the other files individually and zips them into the object
>> (0Mb -> compressed size of all js/html is perhaps around 1-2Mb or
>> under) The library then loads the mp4 (now it has the object = 2Mb and
>> the video = 62Mb in
>> memory) It adds it to the zip object but it's also still in memory
>> (mp4 doesn't compress at all so we have 2 + 62 + 62 =126Mb which is
>> less than
>> 128Mb) It then closes the connection to the mp4 and destroys the
>> object (memory now = 64Mb for the zip)
>>
>> I'm wondering whether a 64 Mb or slightly bigger will cause you to be
>> able to crash that server too. Is that something you could try?
>>
>> Regards,
>>
>> John Smith | Learning Technologist
>> Room A251, Govan Mbeki Building | School of Health & Life Sciences |
>> Glasgow Caledonian University Cowcaddens Road | Glasgow | G4 0BA
>>
>> Please address ALL support requests to hlsblt at gcu.ac.uk where one of
>> the School Learning Technologists will pick up the job. This will
>> ensure that all jobs are completed as promptly as possible.
>> ________________________________________
>> From: xerte-dev-bounces at lists.nottingham.ac.uk
>> [xerte-dev-bounces at lists.nottingham.ac.uk] On Behalf Of Ron Mitchell
>> [ronm at mitchellmedia.co.uk]
>> Sent: 01 May 2014 09:09
>> To: 'For Xerte technical developers'
>> Subject: [Xerte-dev] Re: example_zipper issue revisited
>>
>> Hi John
>> I was just going to test your export code on a server where I don't
>> have access to change php settings so the memory limit is fixed at
>> 128MB. I know what David means that ideally we want cross platform
>> code but as you say there are inevitably different
>> solutions/restrictions for some e.g. no control over memory limit. In
>> fact the upload limit on this particular shared server is set at the
>> default 2MB so I had to upload the test 62MB mp4 via ftp. However I'm
>> now confused further because this is the same XOT code as the other
>> servers I was using for testing so I expected the export to fail when
>> testing before replacing the export code with yours and yet it didn't
>> fail and I was able to download the zip which didn't contain any
> example_zipper files.
>>
>> I'm glad you're able to reproduce the issue but not sure how a server
>> with 128MB memory limit is able to export ok without a change of code
>> or memory limit :-(
>>
>>
>>
>> -----Original Message-----
>> From: xerte-dev-bounces at lists.nottingham.ac.uk
>> [mailto:xerte-dev-bounces at lists.nottingham.ac.uk] On Behalf Of Smith,
>> John
>> Sent: 01 May 2014 08:38
>> To: xerte-dev at lists.nottingham.ac.uk
>> Subject: [Xerte-dev] Re: example_zipper issue revisited
>>
>> All i know Dave is that, with the commented code uncommented, my
>> system couldn't download a 56Mb an 79Mb zip but with this code 79Mb
>> came down no problem.
>>
>> We may have to use what we have access to on different systems. There
>> may be a similar way to pipe the result into windows or we fall back
>> to the old code and crank the memory requirements up yo 300Mb which
>> not everyone can most likely do anyway...
>>
>> Regards
>>
>> John Smith
>> Learning Technologist
>> School of Health and Life Sciences
>>
>> Sent from Samsung Galaxy SII
>>
>>
>>
>> David Goodwin <david at palepurple.co.uk> wrote:
>>
>>
>>
>> <snip>
>> Uses the unix command zip and pipes the stream back into PHP in 8192
>> chunks
>>
>> <snip>
>> Also, might not work on Windows...
>>
>> So therefore it's not worth using?
>>
>>
>> Technically there is no benefit to doing the fread(....) over a
>> fpassthru(...) fpassthru does something like 8192 chunks internally.
>>
>>
>> David.
>>
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