I would like to create a rake task or something to clear the browser cache. The issue is, I am running a Flash app, and if I change the data, I more often than not need to reset the browser cache so it removes the old swf and can see the new xml data.
How do you reset the browser cache with ruby? Or even more precisely, how can I only remove a select item from the browser cache?
Thanks for the help!
I see a few possible solutions:
Write some shell script that deletes the temporary files from disk out the cache (what browser are you using?). I'm am not sure deleting the files on disk will necessarily work if the browser has them cached in memory.
Use and HTTP header (No-Cache) to avoid caching in the browser, Adobe has documentation on No-Cache. You could set this header only in development mode, so that in production the swf is cached.
Depending on your browser, force a page and cache refresh (e.g. Crtl-F5 in Firefox)
I'm not sure how you're loading the xml data, but in the past, I've gotten around the issue by appending a random number to the path of the xml file:
xml.load("data.xml?"+Math.random());
Basically, Flash will always think the file is a different URL. It won't be able to find a match in your cache.
Again, I'm not sure how you're loading the XML data, so I'm not sure if this applies to your situation.
Hope it helps, though.
You cannot reset browser cache, even if you would sometimes it will not be sufficient because caching can occur not only on the server and/or client, but also on any number of nodes your response goes through on its way from your server to your client.
The only tool at your disposal is the caching headers.
You can set them to NoCache just keep in mind that it will be hitting the server every time
Since you're using Safari, here's an article describing how to use AppleScript to clear the cache. But you can probably just skip the AppleScript part and remove the files directly in the rake task. The only catch might be that you have to restart the browser for it to take affect, but that could be done with a kill on the process and an "open /Applications/Safari.app" (I'm assuming you're on a Mac; in Windows it would be something like start "c:\program files\Safari...").
Related
Traditionally a browser will parse HTML and then send further requests to the server for all related data. This seems like inefficient to me, since it might require a large number of requests, even though my server already knows that a browser that wants to use this web application will need all of it's resources.
I know that js and css could be inlined, but that complicates server side code and img data as base64 bloats the size of the data... I'm aware as well that rendering can start before all assets are downloaded, which would potentially no longer work (depending on the implementation). I still feel that streaming an entire application in one go should be faster on slow connections than making tens of requests separately.
Ideally I would like the server to stream an entire directory into one HTTP response.
Does any model for this exist?
Does the reasoning make sense?
ps: If browser support for this is completely lacking, I'm wondering about a 2 step approach. Download a small JavaScript which downloads a compressed web app file, extracts it and plugs the resources into the page. Is anyone already doing something like this?
Update
I found one: http://blog.another-d-mention.ro/programming/read-load-files-from-zip-in-javascript/
I started to research related issues in order to find the way to get best results with what seems possible without changing web standards, and I wondered about caching. If I could send the last modified date of every subresource of a page along with the initial HTML page, a browser could avoid asking if modified headers once it has loaded every resource at least once. This would in effect be better than to send all resources with the initial request, since that would be beneficial only on the first load, and detrimental on subsequent loads, since it would be better for browsers to use their cache (as Barmar pointed out).
Now it turns out that even with a web extension you can not get hold of the if-modified-since header and so you surely can't tell the browser to use the cached version instead of contacting the server.
I then found this post from Facebook on how they tried to reduce traffic by hashing their static files and giving them a 1 year expiry date. This would mean that the url garantuees the content of the file. They still saw plenty of unnecessary if-modified-since requests and they managed to convince Firefox and Chrome to change the behaviour of their reload buttons to no longer reload static resources. For Firefox this requires a new cache-control: immutable header, for Chrome it doesn't.
I then remembered that I had seen something like that before and it turns out there is a solution for this problem which is more convenient than hashing the contents of resources and serving them from a database for at least ten years. It is to just a new version number in the filename. The even more convenient solution would be to just add a version query string, but it turns out that that doesn't always work.
Admittedly, changing your filenames all the time is a nuisance, because files referencing these files also need to change. However the files don't actually need to change. If you control the server it might be as simple as writing a redirect rule to make sure that logo.vXXXX.png will be redirected to logo.png (where XXXX is the last modified timestamp in seconds since epoch)[1]. Now let your template system automatically generate the timestamp, like in wordpress' wp_enqueue_script. WordPress actually satisfies itself with the query string technique. Now you can set the expiration date to a far future and use the immutable cache header. If browsers respect the cache control, you can now safely ignore etags and if-modified-since headers, since they are now completely redundant.
This solution guarantees the browser shall never ask for cache validation and yet you shall never see a stale resource, without having to decide on the expiry date in advance.
It doesn't answer the original question here about how to avoid having to do multiple requests to fetch the resources on the same page on a clean cache, but ever after (as long as the browser cache doesn't get cleared), you're good! I suppose that's good enough for me.
[1] You can even avoid the server overhead of checking the timestamp on every resource every time a page references it by using the version number of your application. In debug mode, for development, one can use the timestamp to avoid having to bump the version on every modification of the file.
It's very important for the website I'm working on to be offline-functional. I'm using a Cache Manifest to store all the files on the application cache, so that takes care of that and all is good and well.
BUT, as I read and noticed myself, the browser first shows the cached version of the site before checking for an update online. Hitting refresh reloads the cache again, with the new cached files this time (or what it had time to update for the swift refreshers).
I'm aware of this fix : http://www.html5rocks.com/en/tutorials/appcache/beginner/, where the user is told an update is available and is asked to refresh the page. Not a bad method, but still sketchy for user experience.
Is there any other way to force the browser to show the most up to date files if online? Would cache busting all files manually AND using a cache manifest fix this problem, or will it conflict with the cache manifest and cause problem to the offline functionality?
I found something that works well for me:
The URL linking to the web page contains a parameter. If there is ever a change to the page or related files, the url is changed to something like this: http:/ /www.mywebsite.com/mypage.html?v=3 where v=3 is changed depending on updates.
This is a longer fix to implement (finding every page affected by a change & changing all their cache busting links), but the pages at least show what they're supposed to on the first load and the cache manifest still load the update for offline viewing.
I made some changes to a CSS file, uploaded it and saw no change. I cleared my browser's cache, repeated the process and still nothing. I also tried another browser and then experimented with other files - all the same result.I then deleted the CSS file altogether - the website still looks the same and I can still see the files in the browser's console.
I can only get results if I actually change the file names altogether (which is really inconvenient). I dont think there is an issue with FTP overwriting the file as there are no errors in FileZillas logs.
Is there another way a website can cache its self? Would anyone know why this is occurring?
EDIT:
I also tried this in cPanel's File Manager and viewed it on another PC - same result
Squid and other web accelerators often sit between a hosted server and your browser. Although they are supposed to invalidate their caches when the backing file changes, that information isn't always sent to specification or acted on properly.
Indeed, there can be multiple caches between you and the server each of which has a chance of hanging onto old data.
First, use Firebug or "Inspect Element" in chrome.
Verify that the css file that the browser is loading the file you think is should load.
Good luck.
Browsers can cache things, did you try SHIFT-F5 on your webpage to force a reload of everything?
Maybe the main server has cached configuration setup to other servers, check with your IT department. If this is the case, you need to tell them to invalidate the cache through all the cached servers.
I had the same issue with fileZilla to solve it you need to clear the file zilla cache or change the name of the files you are uploading.
Open FileZilla and click on the Edit menu.
Choose Clear Private Data.
In the new dialog box, check mark the categories you’d like to clear: Quickconnect history, Reconnect information, Site Manager entries, Transfer queue.
Finally, click OK to validate
Background
I'm building an app that links recent
web pages you've visited together.
To do this, I need to get the HTML
for recent URLs using Cocoa.
Right now, I'm using an invisible
WebView to do this.
As I understand it, if the URL isn't
in the cache for my app, this is
hitting web servers.
What I want
The chances are high that the URL I'm grabbing has already been cached by Safari as the page has already been visited.
I want my app to check Safari's cache for the URL first. If it's there, it should just use this data. If not, it should hit the web server and store the page in my app's cache.
I don't really want to have to parse the cache.db file from Safari using sqlite3 - I've no idea if this format will stay the same. I'm after something simpler and more high level.
What I've tried
I know that you can set up your own NSURLCache using the method initWithMemoryCapacity:diskCapacity:diskPath: but I don't want to try pointing this to the Safari cache in case it screws up Safari by writing to it.
Is there an easy, high level way of sharing the Safari cache?
UPDATE
Aha. I've just realised there may be a way to do this I've been missing.
I could make a new instance of NSURLCache with initWithMemoryCapacity:diskCapacity:diskPath:, point it at the Safari cache, then specify a cache policy of NSURLRequestReturnCacheDataDontLoad for the URL Request when loading the page.
When this fails, I could just try and load the page as normal. I'll try this out and update the question when I know more.
To be honest, you just can't do this.
Firstly, I'm pretty certain -[NSURLCache initWithMemoryCapacity:diskCapacity:diskPath:] won't work as you expect. It will instead blow away the old cache file to create its own; potentially highly upsetting Safari.
Secondly NSURLCache is a composite cache. That is, it caches data first in memory, and then moves it out to disk at some point. So even if you could properly access Safari's cache file (which you can't) you'd only be able to access the older cached data; not the most recent.
Is it possible to clear all site cache? I would like to do this when the user logs out or the session expires instead of instructing the browser not to cache on each request.
As far as I know, there is no way to instruct the browser to clear all the pages it has cached for your site. The only control that you, as a website author, have over caching of a page occurs when the browser tries to access that page. You can specify that cached versions of your pages should expire at a certain time using the Expires header, but even then the browser won't actually clear the page from its cache at that time.
i certainly hope not - that would give the web site destructive powers over the client machine!
If security is your main concern here, why not use HTTPS? Browsers don't cache content received via HTTPS (or cache it only in memory).
One tricky way to mimic this would be to include the session-id as a parameter when referencing any static piece of content on the site. When the user establishes the session, the browser will recognize all the pieces of content as new due to the inclusion of this parameter. For the duration of the session the browser will used the static content in its cache. After the user logs out and logs back in again, the session-id parameter for the static contents will be different, so the browser will recognize this is as completely new content and will download everything again.
That being said... this is a hack and I wouldn't recommend pursuing it.. For what reason do you want the user's cache to be cleared after their session expires? There's probably a better solution that can fit your situation as opposed to what you are currently asking for.
If you are talking about asp.net cache objects, you can use this:
For Each elem As DictionaryEntry In Cache
Cache.Remove(elem.Key)
Next
to remove items from the cache, but that may not be the full-extent of what you are trying to accomplish.