Freewheel

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Active Member
nienberg
Posts: 10
Registered: ‎01-24-2005
Message 1 of 15 (238 Views)

caching gone bad?

238 Views, 14 Replies
05-07-2007 02:34 PM
I'm testing the freewheel web service as a way to display dwf files on our website. One problem I've noticed is that the call to freewheel.autodesk.com is often answered without actually reading the dwf file from my website. (I can see in the webserver access logs when the dwf file is requested). Is this a case of the autodesk server caching the result after it generates the image once? In my case I am getting some empty results when I expect to see an image. I think the first time I requested the image, the dwf file did not exist on my server, but it does now.

Thanks,
*Sam M
Message 2 of 15 (238 Views)

Re: caching gone bad?

05-08-2007 04:19 AM in reply to: nienberg
yes, the data is cached on the freewheel server, cant remember how long for,
think someone said a month.

easiest way to solve is rename the dwf file and update the html-code to
suit. Had the same problem myself, that freewheel still used the cached
data despite the local dwf being a different version - renaming the file to
something new forced it to re-upload the dwf and display the correct
version.


wrote in message news:5577848@discussion.autodesk.com...
I'm testing the freewheel web service as a way to display dwf files on our
website. One problem I've noticed is that the call to
freewheel.autodesk.com is often answered without actually reading the dwf
file from my website. (I can see in the webserver access logs when the dwf
file is requested). Is this a case of the autodesk server caching the
result after it generates the image once? In my case I am getting some
empty results when I expect to see an image. I think the first time I
requested the image, the dwf file did not exist on my server, but it does
now.

Thanks,
Active Member
nienberg
Posts: 10
Registered: ‎01-24-2005
Message 3 of 15 (238 Views)

Re: caching gone bad?

05-08-2007 09:39 AM in reply to: nienberg
Thanks for your confirmation of the problem.

Is this something that Autodesk can fix? I am using freewheel to display a database full of details that are constantly changing. The dwf names correspond to the detail numbers. I could write a bunch of code to append a revision number or something, but that seems like an unnecessary pain in the neck.

Mark
*Scott Sheppard - Autodesk
Message 4 of 15 (238 Views)

Re: caching gone bad?

05-08-2007 09:58 AM in reply to: nienberg
Project Freewheel (http://dwfit.com) and Autodesk Freewheel
(http://freewheel.autodesk.com) obey the cache headers set on your server.
If you set them, we will honor them. If you do not set them, we use a
timeout value of 4.5 days. So in the future, you can set your cache headers
to a shorter time period. For this instance, you can wait 4.5 days.

wrote in message news:5578765@discussion.autodesk.com...
Thanks for your confirmation of the problem.

Is this something that Autodesk can fix? I am using freewheel to display a
database full of details that are constantly changing. The dwf names
correspond to the detail numbers. I could write a bunch of code to append a
revision number or something, but that seems like an unnecessary pain in the
neck.

Mark
Active Member
nienberg
Posts: 10
Registered: ‎01-24-2005
Message 5 of 15 (238 Views)

Re: caching gone bad?

05-08-2007 02:58 PM in reply to: nienberg
Ah, that's interesting. I'll try setting a short cache for the directory that holds dwf files and see if that fixes it. Thanks for your help!
*Sam M
Message 6 of 15 (238 Views)

Re: caching gone bad?

05-09-2007 12:42 AM in reply to: nienberg
as a thought, would it be possible, and easier, to just compare the cached
and users' files dates and sizes? If size is different then either the file
has changed, or even the cached data is possibly incomplete/corrupted.

Just thinking that not everyone has knowledge of cache-headers and this
problem may well re-appear much like the "text doesn't work" comments of
Inventor.

what do you think m8?

"Scott Sheppard - Autodesk" wrote in message
news:5578800@discussion.autodesk.com...
Project Freewheel (http://dwfit.com) and Autodesk Freewheel
(http://freewheel.autodesk.com) obey the cache headers set on your server.
If you set them, we will honor them. If you do not set them, we use a
timeout value of 4.5 days. So in the future, you can set your cache headers
to a shorter time period. For this instance, you can wait 4.5 days.

wrote in message news:5578765@discussion.autodesk.com...
Thanks for your confirmation of the problem.

Is this something that Autodesk can fix? I am using freewheel to display a
database full of details that are constantly changing. The dwf names
correspond to the detail numbers. I could write a bunch of code to append a
revision number or something, but that seems like an unnecessary pain in the
neck.

Mark
*Scott Sheppard - Autodesk
Message 7 of 15 (238 Views)

Re: caching gone bad?

05-09-2007 08:01 AM in reply to: nienberg
Doing things based on file size (could change but have same size) or date
(times on machines vary) is dangerous. For obvious performance reasons, we
don't want our server to go get the DWF file every time. So we pick 4.5 days
as a way to balance performance versus being up to date with DWF file
changes. For people who have DWF files that change frequently, they can set
the cache header to a value like 1 day.

"Sam M" wrote in message
news:5579613@discussion.autodesk.com...
as a thought, would it be possible, and easier, to just compare the cached
and users' files dates and sizes? If size is different then either the file
has changed, or even the cached data is possibly incomplete/corrupted.

Just thinking that not everyone has knowledge of cache-headers and this
problem may well re-appear much like the "text doesn't work" comments of
Inventor.

what do you think m8?

"Scott Sheppard - Autodesk" wrote in message
news:5578800@discussion.autodesk.com...
Project Freewheel (http://dwfit.com) and Autodesk Freewheel
(http://freewheel.autodesk.com) obey the cache headers set on your server.
If you set them, we will honor them. If you do not set them, we use a
timeout value of 4.5 days. So in the future, you can set your cache headers
to a shorter time period. For this instance, you can wait 4.5 days.

wrote in message news:5578765@discussion.autodesk.com...
Thanks for your confirmation of the problem.

Is this something that Autodesk can fix? I am using freewheel to display a
database full of details that are constantly changing. The dwf names
correspond to the detail numbers. I could write a bunch of code to append a
revision number or something, but that seems like an unnecessary pain in the
neck.

Mark
*Sriram Gopalakrishnan - Autodesk
Message 8 of 15 (238 Views)

Re: caching gone bad?

05-11-2007 09:40 AM in reply to: nienberg
Inside the cache-header window doing it based on the size might make sense.
If the dwf has changed, chances of the size being the same is pretty slim.
Even if the size was the same - you are no worse than how its done now.

--
Sriram Gopalakrishnan
DWF
Autodesk
*Scott Sheppard - Autodesk
Message 9 of 15 (238 Views)

Re: caching gone bad?

05-11-2007 09:56 AM in reply to: nienberg
We are trying to strike a balance. Cache headers were made specifically for
this purpose. We don't want our server doing extra work of checking file
size data on the machine where the file is located. We are happy to document
our 4.5 day timeout and let people specify something smaller if they want.
My fear is that thousands of user swill specify ridiculous values of
something like "1 hour" and our machine will get swamped with requests to go
get people's DWF files.

"Sriram Gopalakrishnan - Autodesk" wrote
in message news:5583454@discussion.autodesk.com...
Inside the cache-header window doing it based on the size might make sense.
If the dwf has changed, chances of the size being the same is pretty slim.
Even if the size was the same - you are no worse than how its done now.

--
Sriram Gopalakrishnan
DWF
Autodesk
*Ben Cochran \(Autodesk\)
Message 10 of 15 (238 Views)

Re: caching gone bad?

05-14-2007 08:59 AM in reply to: nienberg
The Freewheel server can simply ask the original web server if the DWF has
changed. The problem is that depending on the speed of the server hosting
the original DWF this check can take up to 2 seconds. When should this check
happen? It would be foolish to check on every pan or orbit. It would also be
foolish to never check the original DWF again. The HTTP spec. solves the
problem by defining cache headers that tell downstream readers how long an
HTTP response is valid. The Freewheel server honors these headers when they
are set. The problem Sam is running into is with what the Freewheel server
does when the HTTP cache headers have not been set. In this case, Freewheel
will check the server that hosts the DWF file after 4½ days. This is a
reasonable compromise between dynamic and static data. Again, to work around
this, set the HTTP cache headers appropriately.

That being said, we are currently working on a solution to this problem, but
I can not go into the details about how it works at this time.

Ben Cochran
Autodesk Labs - Freewheel

"Sriram Gopalakrishnan - Autodesk" wrote
in message news:5583454@discussion.autodesk.com...
Inside the cache-header window doing it based on the size might make sense.
If the dwf has changed, chances of the size being the same is pretty slim.
Even if the size was the same - you are no worse than how its done now.

--
Sriram Gopalakrishnan
DWF
Autodesk
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