Rails - Jun 2006 - Issue with caching of .PNG files in IE..

I''m running a Rails  application with WEBrick server. We are displaying
an Image from the server to the Client (Browser). First time on the 
browser everything looks fine, upon clicking the link, it contacts the 
server and displays in IE brwoser the image that was stored on the 
server.

But in case if the image gets changed on the server(File Name being the 
same), then even though i click the refresh button on IE, the Browser 
still Loads the old image !!!.  Has any body seen the above problem.  I 
think IE is caching the IMAGE file and it does not clear the chache even 
though i click the link or refresh the whole page to get the new image 
from the server?

Any ideas? kindly pl let me know..

I''m running on Webrick Server.

Thank You,
Dinesh

-- 
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On Jun 16, 2006, at 9:19 PM, Dinesh Umanath wrote:
> But in case if the image gets changed on the server(File Name being the
> same), then even though i click the refresh button on IE, the Browser
> still Loads the old image !!!.  Has any body seen the above problem.  I
>
How are you sending the image? I use send_data, and switch off the 
cacheing completely (because my image is generated again for every 
request)

         # Explicitly switch off image cacheing
         expires_now
         send_data(session[:image], :type=>"image/png", 
:disposition=>"inline")

This isn''t a good solution for images that only change *sometimes*, but
it might help you to find a better solution.

-jim

Dinesh Umanath wrote:
> Any ideas? kindly pl let me know..
> Thank You,
> Dinesh
You might want to try setting the IE cache setting within IE''s Options 
to ''Every visit to the page'' - I know that in the past having
it set to
''Automatic'' would cause problems seeing updates even when I
was
specifically refreshing the page

hope it helps,
Chris


-- 
Posted via http://www.ruby-forum.com/.

Hi Jim,

Thanks for your reply.

In the "show.rhtml" page i''m having this code which uses AJAX
to get the
image Asynchronously . After that the image is rendered to the client..

****************************************************************************
show.rhtml
-----------
<%= link_to_remote(:update => ''updatediv'',
 		   :url => { :action => :get_images }) %></td>
<div id="updatediv"></div>

****************************************************************************
In the "contoller" i''m having this action

  def get_images
 	@responseImage="/images/myImages/Image1.png"
  end
****************************************************************************

In the "view" i''m having this code..
<%= @responseImage %>
****************************************************************************

So can  send_date or send_file can solve the above problem ??

Thank You,
Dinesh


Jim Cheetham wrote:
> On Jun 16, 2006, at 9:19 PM, Dinesh Umanath wrote:
>> But in case if the image gets changed on the server(File Name being the
>> same), then even though i click the refresh button on IE, the Browser
>> still Loads the old image !!!.  Has any body seen the above problem.  I
>>
> How are you sending the image? I use send_data, and switch off the
> cacheing completely (because my image is generated again for every
> request)
> 
>          # Explicitly switch off image cacheing
>          expires_now
>          send_data(session[:image], :type=>"image/png",
> :disposition=>"inline")
> 
> This isn''t a good solution for images that only change
*sometimes*, but
> it might help you to find a better solution.
> 
> -jim

-- 
Posted via http://www.ruby-forum.com/.

Hi Chris,

Thanks for the reply.

I''m already having the Setting on my browser as ''Every visit
to the
page''.

But still no luck!! Any other ways ?

Dinesh

Chris wrote:
> Dinesh Umanath wrote:
> 
>> Any ideas? kindly pl let me know..
> 
>> Thank You,
>> Dinesh
> 
> You might want to try setting the IE cache setting within IE''s
Options
> to ''Every visit to the page'' - I know that in the past
having it set to
> ''Automatic'' would cause problems seeing updates even when
I was
> specifically refreshing the page
> 
> hope it helps,
> Chris

-- 
Posted via http://www.ruby-forum.com/.

On Jun 16, 2006, at 10:09 PM, Dinesh Umanath wrote:
> So can  send_date or send_file can solve the above problem ??
Erm, no ... but expires_now may still help, in controller method 
get_images.

Jim,

In your case you are also displaying the image finally in the browser 
itself rt may be in a''div'' element using
''send_data''? with "inline"
otion, then it should work for me also rt?

Dinesh

Jim Cheetham wrote:
> On Jun 16, 2006, at 10:09 PM, Dinesh Umanath wrote:
>> So can  send_date or send_file can solve the above problem ??
> 
> Erm, no ... but expires_now may still help, in controller method
> get_images.

-- 
Posted via http://www.ruby-forum.com/.

On Jun 16, 2006, at 11:51 PM, Dinesh Umanath wrote:
> In your case you are also displaying the image finally in the browser
> itself rt may be in a''div'' element using
''send_data''? with "inline"
> otion, then it should work for me also rt?
Yes -- my controller''s view generates an <img> tag which is a
reference
to another controller method, which uses send_data to return the image 
inline. You could do that if you wanted to :-) However, just using 
''expires_now'' for every image is a bit of a large hammer; it
depends on
how often your images really change, and how much caching you want the 
clients to be able to do.

<img src="<%=
url_for({:action=>''reflectpng'',:id=>@image.id})
%>" />

and it''s method ''reflectpng'' that used send_data.

-jim

2006/6/16, Dinesh Umanath <u_dinesh@yahoo.com>:
> I''m running a Rails  application with WEBrick server. We are
displaying
> an Image from the server to the Client (Browser). First time on the
> browser everything looks fine, upon clicking the link, it contacts the
> server and displays in IE brwoser the image that was stored on the
> server.
>
> But in case if the image gets changed on the server(File Name being the
> same), then even though i click the refresh button on IE, the Browser
> still Loads the old image !!!.  Has any body seen the above problem.  I
> think IE is caching the IMAGE file and it does not clear the chache even
> though i click the link or refresh the whole page to get the new image
> from the server?
>
> Any ideas? kindly pl let me know..
>
> I''m running on Webrick Server.
image_tag or image_path can do this. or:
<img src="<%=
"web_path.png?#{File.mtime(full_path.png).to_i}" %>" />

Hi Jim

Thanks for your response. I tried with send_data using the <img> tag and
it works fine !!!.

But my  problem is i want to do it through AJAX, and i''m not sure how
to
do it with AJAX.

ie. when we call the  link_to_remote(...), it emits the output using the
:update

ie. we can define an empty <div id="updatediv"></div> like
this and we
can ask :update=>''updatediv'', which will emit the output of
link_to_remote into the div element which is fine.

But in our case, in the contoller i''m using send_file like this
send_file(''public/images/myImage.png'',type=>"image/png",:disposition=>"inline"),
so the AJAX when it receives this file it will update in the
''updatediv''
element. But i want to use <img> tag here, ie get the updates from AJAX
and update it using the <img> tag, i still dont know whethere it makes
sense or not.

ie. bottom line -> AJAX + send_file + <img> tag is what i''m
trying to do
so that i will..but still no luck and struggling..:)


Thanks again for your kind replies..

Dinesh



Jim Cheetham wrote:
> On Jun 16, 2006, at 11:51 PM, Dinesh Umanath wrote:
>> In your case you are also displaying the image finally in the browser
>> itself rt may be in a''div'' element using
''send_data''? with "inline"
>> otion, then it should work for me also rt?
> 
> Yes -- my controller''s view generates an <img> tag which is
a reference
> to another controller method, which uses send_data to return the image
> inline. You could do that if you wanted to :-) However, just using
> ''expires_now'' for every image is a bit of a large hammer;
it depends on
> how often your images really change, and how much caching you want the
> clients to be able to do.
> 
> <img src="<%=
url_for({:action=>''reflectpng'',:id=>@image.id})
%>" />
> 
> and it''s method ''reflectpng'' that used
send_data.
> 
> -jim
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On Mon, Jun 19, 2006 at 09:00:38AM +0200, Guest wrote:
> But in our case, in the contoller i''m using send_file like this
>
send_file(''public/images/myImage.png'',type=>"image/png",:disposition=>"inline"),
> so the AJAX when it receives this file it will update in the
''updatediv''
> element. But i want to use <img> tag here, ie get the updates from
AJAX
> and update it using the <img> tag, i still dont know whethere it
makes
> sense or not.
I had a really ugly solution to this, with the original ajax call
returning the HTML <img>, and passing in some parameters to the src of
the image tag ... but I suspect you would be able to simplify this using
RJS these days. RJS gets rid of the :update argument, and gives you a
pure Ruby environment where you can update as many different page
sections as you like ... 

But this isn''t really a cacheing question any more, so perhaps starting
a new message thread asking about that would be a good idea.

-jim