HTML 5 offline logic is encapsulated in window.applicationCache object. However it looks like it's not possible to programmatically clear cache data, for example, when user logs off from the system. Is there any other way to clear HTML 5 application cache, except for generating empty manifest file?
Have observed this on Chrome not sure if that's the standard way, if server responds with 404 on manifest file request, cache gets cleared from browser after raising obsolete event.
Setting aside the specifics of the HTML5 appcache, clearing a browser's cache programmatically has never been possible (beyond certain ActiveX controls for that browser) so I suspect you may come up empty on this one. Perhaps you should focus on the cache control meta tag and test further with your empty manifest idea?
I think the best way to do this is to change the link to the manifest file. In this case I would append the user's session ID to the manifest file. Every user should have session regardless of logged in status and the session ID should probably changed when logging in/out (maybe).
I also found this answer: Removing HTML5 Appcache Manifest, Permanently
Related
In one of the online documents that talks about appcache for HTML5, it indicates that the cached files get updated once an offline user reconnects. I checked the original HTML5 appcache definition by W3, and I am not able to find anything that supports this statement.
Does anyone know if this is to be true?
Thanks in advance
MDN says the following, although if you scroll up on that page it says it's being deprecated.
If an application cache exists, the browser loads the document and its associated resources directly from the cache, without accessing the network. This speeds up the document load time.
The browser then checks to see if the cache manifest has been updated on the server.
If the cache manifest has been updated, the browser downloads a new version of the manifest and the resources listed in the manifest. This is done in the background and does not affect performance significantly.
And logic tells me that it would also depend on the app you're using, server you're trying to connect to and any special settings it might have, how long your browser keeps it's history, what it keeps, and if you saved the page to view offline - whether or not you have all the code/images saved in the right location(s).
Example:
Imagine you saved a page to view offline, and that page has a JS event handler that ran a while loop that did an ajax request every n seconds to do something, like make a number on a page change as long as you were online... As long as the loop is running, you suddenly connect to the internet, and it makes the request to the proper url with the right arguments, then it should go through, even though the url in your browser might say something like file:///C:/Users/you/Desktop/....
I've done this before, even though my url was like the one above. One time I was using braintree's drop-in javascript to a website, and using it's api on my backend. Trying to load the page when offline = Nothing. Online = Updated the spot on the page just fine when I had the required arguments, and it was pointing to the right url. If I got offline again, I could refresh the page, see the same images loaded in the <div>, but I couldn't send any data with it.
I am testing HTML5's offline capabilities, and the cache seems to be a bit overactive. My cache.appcache file is as follows:
CACHE MANIFEST
CACHE:
#v1.4
js/js.js
NETWORK:
network2.html
FALLBACK:
/ offline.html
Basically I want to only display network2.html when the web is available - otherwise it should fall back to offline.html.
However, if I have accessed network2.html with the web connection live it keeps displaying it when there is no connection - surely it should fall back to offline.html? I thought only pages referenced in the CACHE section should be cached in the first place anyway?
I have tried in multiple browsers, clearing the browser data, refreshing multiple times etc.
Sorted it - it turns out that any file whose html tag references the manifest will be cached itself, whether or not that file is mentioned in the CACHE section. This even overrides if it is referenced in the NETWORK section.
Thanks to robertc on this answer which gave me the tip.
In short, you only need to have one reference to the manifest, usually in your 'default' view, not all files that may be referenced by the manifest itself. Not very clear in the HTML5 docs.
I have been trying to figure out HTML5's new AppCache, but I feel extremely limited here.
Let's assume that I have a website with four pages:
index.html
about.html
portfolio.html
contact.html
I have the above resources outlined in the manifiest, along with all of the website's resources. The manifest looks like the below:
CACHE MANIFEST
# 2013-05-23 2:33 PM
# Master Manifest
index.html
about.html
portfolio.html
contact.html
styles/reset.css
styles/styles.css
NETWORK:
*
I have added the appcache file type to the server configuration and have used the correct HTML tag attribute on each page listed above. Just for the record, the element looks like so:
<html lang="en" manifest="example.appcache">
I have tested this setup out on my mobile device, and everything works perfectly fine... Unless I don't load every page. It seems that I have to go to each page and cache it via my mobile browser, after which I may turn off DATA and go offline for my device to be able to browse the APPCACHE'd website.
But, here's my question - How do I setup AppCache to allow me to go to index.html, cache that page, and cache the rest of the resources in the manifest? Without having to visit and manually cache each resource?
If you cannot, then I would have to ask; doesn't that sort of defeat the idea behind AppCache and Offline Accessibility?
Thank you so much for the help all! :)
You shouldn't need to visit every page. I know you mentioned you've set the MIME type in Apache, but are you 100% certain it's working correctly?
You can check it by opening your manifest in a browser and checking the Response Headers in Chrome Web Inspectors's Network tab:
Content-Type should be text/cache-manifest
It's a bit hard to debug without having access to your site, but here's some instructions for how to interpret what happens in Chrome's Web Inspector with AppCache to help you debug the problem yourself:
The Resources tab will show you the contents and status of the Application Cache. It looks like this whilst it's downloading files:
The console will also log events when it's downloading:
Application Cache Progress event (0 of 48) http://cachedfile.url
Once it's done downloading it'll look like this and show you the list of cached files:
When you go back it'll log three events (assuming there aren't any changes):
Document was loaded from Application Cache with manifest http://manifest.url
Application Cache Checking event
Application Cache NoUpdate event
And then when you're offline it looks like this:
Hopefully between the console and the appcache table you'll be able to figure out what's happening.
The manifest file is correct and you do not need to visit each page to get in cache in your mobile. You could try if this is a problem with your mobile or browser and if you have defined in your server text/cache-manifest MIME type.
The appcache will only store the cache the first time it's downloaded. It's just a list of files that says, when it's downloaded the first time, cache it.
What you could do is after load in the background do an ajax call to load each of the intended resources but it's not particularly pretty.
So looks to me like it's acting how it should be.
CACHE:
This is the default section for entries. Files listed under
this header (or immediately after the CACHE MANIFEST) will be
explicitly cached after they're downloaded for the first time.
http://www.html5rocks.com/en/tutorials/appcache/beginner/
Ahmed
I get the following when visiting your site:
Creating Application Cache with manifest
http://www.iamaaron.com/appcache/example.appcache
Application Cache Checking event
Application Cache Downloading event
Application Cache Progress event (0 of 6)
http://www.iamaaron.com/appcache/styles/reset.css
Application Cache Progress event (1 of 6)
http://www.iamaaron.com/appcache/index.html
Application Cache Progress event (2 of 6)
http://www.iamaaron.com/appcache/contact.html
Application Cache Progress event (3 of 6)
http://www.iamaaron.com/appcache/attendees.html
Application Cache Progress event (4 of 6)
http://www.iamaaron.com/appcache/events.html
Application Cache Progress event (5 of 6)
http://www.iamaaron.com/appcache/styles/styles.css
Application Cache Error event: Resource fetch failed (404)
http://www.iamaaron.com/appcache/styles/styles.css
So, it looks like it's working correctly despite the Content-Type being empty, except for the CSS file which seems to be missing (the URL is wrong, it should be main.css by the looks of things).
BUT my developer tools don't show the app cache being filled and it doesn't work when it's offline.
Try and fix your 404 error with the CSS and make sure your apache it configured correctly to return the correct Content-Type, I reckon that's what's causing issues.
When setting the prefer-online setting I expect the browser to request the page at every refresh of the browser, but it is not the case.
Here is my manifest :
CACHE MANIFEST
SETTINGS:
prefer-online
NETWORK:
*
Yet when I refresh the browser it only requests the manifest to the server. It only requests the page when I update the manifest ...
And there is no headers (expires or max-age) set on the page.
(tested on chrome & firefox)
NB: When updating the manifest, the browser re downloads the assets, but still displays the old version ... It is only on the next load that the browser uses the new assets. Why ?
I don't see what the AppCache manifest is for, since you want to bypass the cache and just use the network. Keep in mind that the regular caching might still apply, regardless of the AppCache manifest, so check the Expires, Last-Modified and similar headers.
As for your question:
NB: When updating the manifest, the browser re downloads the assets, but still displays the old version ... It is only on the next load that the browser uses the new assets. Why ?
This is because the user agent will immediately use the latest cached version of your assets, then start checking the linked resources listed in the manifest for updates. When the user agent detects that the manifest has changed, and thus it has to check for updates, it will fire a checking event.
When the update checking process has finished (and it might take a long time, if you have lots of resources) it will fire an updateready event. Only the resources fetched after this event will be the fresh new ones (that's why it's usually adviceable to use window.applicationCache.swapCache() to tell the browser to swap the old cache for the new for the next page load, or simply reload the page and be done with it).
You will find more detailed explanations about these topics here: http://www.html5rocks.com/en/tutorials/appcache/beginner/
Gurus of SO
I am trying to play with CACHE MANIFEST/HTML5. My app is JS heavy and built on jquery/jquerymobile.
This is an excerpt of what my Manifest looks like
CACHE MANIFEST
FALLBACK:
/
NETWORK:
*
CACHE:
/css/style.css
/js/jquery.js
But somehow, the app doesn't load the files the first time itself and the entire app breaks down.
Is my format wrong?
Should I never load JS into the Cache?
How should I treat this differently to always check the network first if anything isn't available and only load stuff available from the Cache?
Thank you.
I tried a simple page with your cache manifest and it worked fine for me, so I'm not really sure what the problem is. But,
Yes, there is something wrong with the format. The entries in the FALLBACK section need to have two parts: a pattern, and a URL. This says "if any page matching the pattern is not available offline, display the URL instead (which will be cached)." The main example of this (as shown here) is "/ /offline.html", which means "for all pages, if we are offline and they are not cached, display /offline.html instead." However, I don't think this is the source of your problem since I tested it with your exact manifest and it still worked.
There is nothing special about JS files. It should be fine to load them into the cache.
I don't understand the third question. There are possibly two goals here: a) how do you check to see if there is a newer version of the file available online first, before going back to the cache, and b) how do you check the network to see if there is a file that is not cached, and if we are offline, fall back to an error page. The answer to (a) is that once you have turned on the cache manifest, things work very differently. It will never check for new versions of the files unless there is a new version of the manifest also. So you must always update the manifest whenever you change any files. The answer to (b) is the FALLBACK section.
See Dive Into HTML5's excellent chapter on this, particularly the section "The fine art of debugging, a.k.a. “Kill me! Kill me now!”" which explains how the manifest updates.
Also I don't think we've gotten to the meat of your question, because it's unclear what you mean by "the app doesn't load the files the first time itself". Which files don't load? Do they load properly after a refresh? Etc.
The only way I got this to work to refresh a cache was to rename the manifest file with a commit number or timestamp, and change the cache declaration to
<html manifest='mymanifest382330.manifest'>
I made this part of my build.