image in <img> tag is not refreshed

pdl_babu has asked for the wisdom of the Perl Monks concerning the following question:

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Re: image in <img> tag is not refreshed by BrowserUk (Patriarch) on Nov 12, 2005 at 15:45 UTC
Are you using the same name for the .jpg file each time you create a new one? If so, the browser is probably not asking the server for the new one because it thinks it already has it in it's cache. Use a new name each time you create a new jpg. The md5 of the .jpg might make a good choice, or use File::Temp. Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal? "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply]
Re: image in <img> tag is not refreshed by nobull (Friar) on Nov 12, 2005 at 15:46 UTC
Your problem has nothing to do with Perl. Use a different file name for your .jpg each time. This not only solves your problem but also the race condition that exists if two users are accessing your site at the same time. It does create a need to garbage collect your tempory image directory from time to time. Alternatively make the `<img>` tag point to another CGI script that creates the JPEG entity on-the-fly and never saves it as a file. Did I mention that this has nothing to do with Perl?	[reply] [d/l]
Re: image in <img> tag is not refreshed by Tanktalus (Canon) on Nov 12, 2005 at 17:41 UTC
Alternately, don't produce the chart at all - have that done in another runmode (using CGI::Application terms) or another CGI script or whatever. And then set the cache time to 0 in your headers before printing it out. This prevents the race condition mentioned above, eliminates the client's tendency to cache it, and probably allows you to use the server CPU time more effectively (since these will be two processes rather than one), and also start sending back the HTML sooner (since producing the chart won't completely stop producing the HTML). CGI scripts can send back images just fine - you just have to manipulate the header appropriately.	[reply]
Re: image in <img> tag is not refreshed by davidrw (Prior) on Nov 12, 2005 at 15:44 UTC
Can you show the code that generates the `<img>` tag? Is it always `<img src="yourreport.jpg">` or is it like `<img src="report20050105-20050120.jpg">`? If the first one, then it's probably a caching issue .. if the second, probably an issue with your chart generation (maybe not passing in the new date range properly or something like that, but just guessing w/o seeing code)	[reply] [d/l] [select]
Re: image in <img> tag is not refreshed by sulfericacid (Deacon) on Nov 13, 2005 at 03:19 UTC
Hi. An easy solution would be to use a three digit random number and append it to the image. `<img src="image.jpg?123"> <img src="image.jpg?526"> <img src="image.jpg?083">` [download] It'll load the image each time. I used this fix a while back. Hope it helps. "Age is nothing more than an inaccurate number bestowed upon us at birth as just another means for others to judge and classify us" sulfericacid	[reply] [d/l]
Re: image in <img> tag is not refreshed by slayven (Pilgrim) on Nov 13, 2005 at 15:14 UTC
Like in the previous contributions I'm asuming that you're not changing the image filename so when the browser reloads it takes the image from its cache ignoring the changes. Now, to prevent the browser to cache your images just tell him to do it. Put the following Meta-Tag into your HEAD section of your HTML code. `<head> <META HTTP-EQUIV="CACHE-CONTROL" CONTENT="NO-CACHE" /> </head>` [download] ^{-- slayven trust in bash but tie your camel}	[reply] [d/l]
Re^2: image in <img> tag is not refreshed by Anonymous Monk on Nov 13, 2005 at 15:53 UTC
that is html, and only affects the html file, not the image	[reply]
Re^3: image in <img> tag is not refreshed by Anonymous Monk on Nov 13, 2005 at 18:06 UTC
Hi, I just recently had a similar problem. To solve it, I added a .htaccess file to the directory with the images with the following content: `### activate mod_expires ExpiresActive On ### Expire .gif's immediately (0) after they have been accessed (A) ExpiresByType image/gif A0 ### or set "ExpiresDefault" for all files in the directory` [download] more on that here: http://www.apacheref.com/ref/mod_expires.html see ye, svenXY (currently not logged in)	[reply] [d/l]