I have an issue with offline cache manifests that I don't quite know how to troubleshoot.
1) A .json file which is part of the manifest is stored together with the manifest.
2) I change that file, and verify that it is indeed changed on the server.
3) I re-generate the manifest (it has a timestamp for uniqueness)
4) The chrome://appcache-internals show that the manifest is indeed updated at the expected time
5) The .json file is still in the old verison, ie. different from the version I have on server, even though the manifest itself is verified to have been updated minutes later.
I don't understand while one file of the manifest is still in the old version.
Update:
It seems to primarily be a problem on localhost, on my DEV environment
My issue was that I had two different sites on the same domain serving different cache manifests. They seem to block one another out. By clearing the manifest from site one, site two works like expected and vice versa.
I guess the offline cache specs is only intended for one manifest per domain.
Related
I changed my cache.manifest file to the following:
CACHE MANIFEST
NETWORK:
*
CACHE:
FALLBACK:
This triggered an update to my site.
I tried adding a "#" to the manifest file and then removed the manifest="cache.manifest"from my page.
This triggered the cache to be updated again, even though the reference to the manifest was gone. The console indicated it was still being loaded from cache.
I even tried renaming my cache.manifest file and it still was being loaded from cache.
How in the world can I safely stop using cache manifest? I have a completely new version of my site I want to roll out, but if cache manifest is still trying to cache the new site, that will be a disaster for all my visitors who do not know they need to clear their browser cache.
I believe I found the trick.
It seems I need to keep the old cache.manifest but change (not remove) the reference to a non-existent manifest file.
Presumably, I'll need to keep the broken reference there for several years in case I have visitors who only visit periodically.
It seems that if the cache manifest on the server changes it will re-download everything in file? Is there any way to only make it re-download some of the files? If I only make code fixes to a script and then update the manifest (say just put a timestamp comment in it) to force local copies to see a change has been made, I might not want images re-downloaded that haven't changed but still need to be in the manifest. Is there a way to get more precision around this or is it an all or nothing thing?
From what i've expreienced, updating the cache manifest doesn't explicitly download all the content again, but rather checks if they've been modified. So if there are 10 items in your cache manifest and you were to update a single file (and also the manifest file), then each file would be checked for modification, and depending on how they are being served (CDN?) they should be returning a 304 Not Modified, and thus not be downloaded again.
I'm using HTML5 appcache and mostly it's working well. However, sometimes, users' browsers (Chrome or Safari) will hold onto the cached manifest file even though I'm positive that the server has a brand new manifest file with a unique version number inside of a comment (like with "# app version 1.0.0.8" or whatever).
In IIS (version 6), the content expiration was set to 1 day, so could that be the problem? I can't seem to reproduce this issue which makes debugging difficult. As a precaution, in IIS I've changed the content expiration to "expire immediately" for the directory that stores the manifest file. Could that explain why some browsers were hanging onto manifest files even when a new version was available?
I also noticed that when a browser was behaving this way, even if I deleted the manifest file on the server, the user's browser would use its own cached copy of the manifest file which isn't supposed to happen if the file is no longer available in my understanding.
Thanks,
Andy
Taken from my answer here : https://stackoverflow.com/a/13282735/727575
Yes, this is the current "correct" behaviour. It has nothing to do with IIS content expiration. This is what happens:
When you just made changes to the manifest file, and you refresh the browser, this is what happens (assuming you're online)
the browser first loads back all the files in the cache
then the browser check online for your manifest file
it detects that the manifest file has changed, it will then proceed to download the new files
however, keep in mind, at this time, you will still be looking at your 'old files' because the browser has loaded the old files before going online to download the 'new files'
if at this point, if you hit refresh again (2nd time), you should get the 'new files'
This is currently the standard behaviour. Some people put some event handlers to prompt the user to do another refresh (after the 1st refresh)
So basically, you need to refresh twice or throw one of the event from 'window.applicationCache' to handle it
To look at an example of using window.applicationCache, go here : http://www.html5rocks.com/en/tutorials/appcache/beginner/
it's under the "Updating the Cache" section.
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.
Every URL can be linked to a single cache manifest. But I want several cache manifests linked to a same URL. Here is the reason:
Some files I want to be cached are rarely updated and large.
So everytime the cache gets updated these large files get re-downloaded even though they may not have been changed.
So I want to split up the cache. One cache for theses rarely updated large files and another cache for the often updated light files.
Do you guys have any idea how to split up an HTML5 cache?
The most efficient way is:
a) Use far-future expiration date (max-age) on all resources mentioned in manifest's CACHE section and add timestamp suffix to each file in the CACHE section, e.g.:
CACHE:
menu_1355817388000.js
toolbar_1355817389100.js
b) When any of the above files change on the server, regen/update manifest to change the timestamp. Only the file with the modified timestamp will get downloaded next time. Mission accomplished.
Note: Reload the page twice in the browser, as on the first refresh browser downloads just the manifest and uses old cached resources to paint the page. This is done to speed up displaying the page (there are tricks to handle this issue of double refresh, but they are outside the scope of your question)
See more info in this long but best article I ever seen on appcache.
Use an iframe
Your page's cache manifest would include the light files and the cache manifest of an iframe loaded by this page would include the large files
On chrome the iframe's application cache will also be used for the page. I didn't tested this method on other browsers yet.
see a live example at http://www.timer-tab.com and if you are using chrome see its split up cache at chrome://appcache-internals/
When the manifest file is changed and the files of the application cache are downloaded again, the normal HTTP caching rules still apply. This means that if you set the correct HTTP caching headers for these large files, you'll get a 304 so these files are not downloaded again. So it's not necessary to split the application cache.
Maybe an answer but I'd more like to shed some light on my findings as a I troubleshoot my own webapp.
I've discovered that I can use 2 iframes (manifest_framework) and (manifest_media) to load the manifests, but i'm still not exactly clear how they are targetted, but I had limited success.
manifest_framework:
CACHE MANIFEST
CACHE:
appdata.ini
dialog.png
jquery.min.js
login.htm
login.js
manifest.appcache.js
NETWORK:
*
FALLBACK:
manifest_media:
CACHE MANIFEST
CACHE:
manifest_fwk.php
od/audio_track_1_1.m4a
od/audio_track_1_2.m4a
od/audio_track_1_3.m4a
od/audio_track_1_4.m4a
od/video_1.mp4
od/video_2.mp4
od/video_3.mp4
NETWORK:
*
FALLBACK:
./ webapp.php
./index.php is the page the 'landing page' which itself isn't cached but falls back to webapp.php when offline.
What I don't understand is how these link to the webapp.php page.
I am finding I can only get access to one or the other manifests cache.
The above works in mobile safari, the media would be cached, and image but not necessarily the JS or images in the framework manifest.
Anyone have more examples where multiple manifests are referenced from the one URL/page?
The W3C working group has abandoned the file system api, so it SHOULD NOT BE USED anymore.
We'll likely see it fall off the next version of Chrome.
http://www.w3.org/TR/file-system-api/
CACHE MANIFEST
# This is a comment.
# Cache manifest version 0.0.1
# If you change the version number in this comment,
# the cache manifest is no longer byte-for-byte
# identical.
demoimages/mypic.jpg
demoimages/yourpic.jpg
demoimages/ourpic.jpg
sr/scroll.js
NETWORK:
# All URLs that start with the following lines
# are whitelisted.
# whitelisted items are needed to help the site function, you could put regularly
# changing items here
http://example.com/examplepath/
http://www.example.org/otherexamplepath/
CACHE:
# Additional items to cache.
demoimages/allpics.jpg
FALLBACK:
demoimages/currentImg.jpg images/stockImage.jpg`
If the Iframe trick does not work, use the HTML5 FileSystem API
See http://updates.html5rocks.com/2012/04/Taking-an-Entire-Page-Offline-using-the-HTML5-FileSystem-API