When I'm developing my gwt project without a network connection, is there a way to detect this? For example, I have a widget that has an Image in it, and the widget does not display until the Image url request times out (takes a long time, like 2 minutes?).
Also, whenever I refresh the page in hosted mode, it doesn't finish loading for about a minute, when no network connection - seems like gwt is trying to contact some external website and blocking on that until it times out too - making things really slow - any way to stop that too?
Thanks
I'm using gwt-2.1.1, and I haven't encountered any problems when developing offline.
(Although I don't use external resources which are unavailable when there is no internet connection, so maybe you should try to pack the external resources into your project.)
Related
I've got a browser game and I have recently started adding audio to the game.
Chrome does not load the whole page and gets stuck at "91 requests | 8.1 MB transferred" and does not load any more content; and it even breaks the website in all other tabs, saying Waiting for available socket.
After 5 mins (exactly) the data are loaded.
This does not happen on any other browser.
Removing one MP3 file (the latest added one) fixed the problem, so is it perhaps a data limit problem?
Explanation:
This problem occurs because Chrome allows up to 6 open connections by default. So if you're streaming multiple media files simultaneously from 6 <video> or <audio> tags, the 7th connection (for example, an image) will just hang, until one of the sockets opens up. Usually, an open connection will close after 5 minutes of inactivity, and that's why you're seeing your .pngs finally loading at that point.
Solution 1:
You can avoid this by minimizing the number of media tags that keep an open connection. And if you need to have more than 6, make sure that you load them last, or that they don't have attributes like preload="auto".
Solution 2:
If you're trying to use multiple sound effects for a web game, you could use the Web Audio API. Or to simplify things, just use a library like SoundJS, which is a great tool for playing a large amount of sound effects / music tracks simultaneously.
Solution 3: Force-open Sockets (Not recommended)
If you must, you can force-open the sockets in your browser (In Chrome only):
Go to the address bar and type chrome://net-internals.
Select Sockets from the menu.
Click on the Flush socket pools button.
This solution is not recommended because you shouldn't expect your visitors to follow these instructions to be able to view your site.
Looks like you are hitting the limit on connections per server. I see you are loading a lot of static files and my advice is to separate them on subdomains and serve them directly with Nginx for example.
Create a subdomain called img.yoursite.com and load all your images
from there.
Create a subdomain called scripts.yourdomain.com and load all your JS and CSS files from there.
Create a subdomain called sounds.yoursite.com and load all your MP3s from there... etc..
Nginx has great options for directly serving static files and managing the static files caching.
The message:
Waiting for available socket...
is shown, because you've reached a limit on the ssl_socket_pool either per Host, Proxy or Group.
Here are the maximum number of HTTP connections which you can make with a Chrome browser:
The maximum number of connections per proxy is 32 connections. This can be changed in Policy List.
Maximum per Host: 6 connections.
This is likely hardcoded in the source code of the web browser, so you can't change it.
Total 256 HTTP connections pooled per browser.
Source: Enterprise networking for Chrome devices
The above limits can be checked or flushed at chrome://net-internals/#sockets (or in real-time at chrome://net-internals/#events&q=type:SOCKET%20is:active).
Your issue with audio can be related to Chrome bug 162627 where HTML5 audio fails to load and it hits max simultaneous connections per server:proxy. This is still active issue at the time of writing (2016).
Much older issue related to HTML5 video request stay pending, then it's probably related to Issue #234779 which has been fixed 2014. And related to SPDY which can be found in Issue 324653: SPDY issue: waiting for available sockets, but this was already fixed in 2014, so probably it's not related.
Other related issue now marked as duplicate can be found in Issue 401845: Failure to preload audio metadata. Loaded only 6 of 10+ which was related to the problem with the media player code leaving a bunch of paused requests hanging around.
This also may be related to some Chrome adware or antivirus extensions using your sockets in the backgrounds (like Sophos or Kaspersky), so check for Network activity in DevTools.
simple and correct solution is put off preload your audio and video file from setting and recheck your page your problem of waiting for available socket will resolved ...
if you use jplayer then replace preload:"metadata" to preload:"none" from jplayer JS file ...
preload:"metadata" is the default value which play your audio/video file on page load thats why google chrome showing "waiting for available socket" error
Our first thought is that the site is down or the like, but the truth is that this is not the problem or disability. Nor is it a problem because a simple connection when tested under Firefox, Opera or services Explorer open as normal.
The error in Chrome displays a sign that says "This site is not available" and clarification with the legend "Error 15 (net :: ERR_SOCKET_NOT_CONNECTED): Unknown error". The error is quite usual in Google Chrome, more precisely in its updates, and its workaround is to restart the computer.
As partial solutions are not much we offer a tutorial for you solve the fault in less than a minute.
To avoid this problem and ensure that services are normally open in Google Chrome should insert the following into the address bar: chrome: // net-internals (then give "Enter"). They then have to go to the "Socket" in the left menu and choose "Flush Socket Pools" (look at the following screenshots to guide http://www.fixotip.com/how-to-fix-error-waiting-for-available-sockets-in-google-chrome/)
This has the problem solved and no longer will experience problems accessing Gmail, Google or any of the services of the Mountain View giant. I hope you found it useful and share the tutorial with whom they need or social networks: Facebook, Twitter or Google+.
Chrome is a Chromium-based browser and Chromium-based browsers only allow maximum 6 open socket connections at a time, when the 7th connection starts up it will just sit idle and wait for one of the 6 which are running to stop and then it will start running.
Hence the error code ‘waiting for available sockets’, the 7th one will wait for one of those 6 sockets to become available and then it will start running.
You can either
Clear browser cache & cookies (https://geekdroids.com/waiting-for-available-socket/#1_Clear_browser_cache_cookies)
Flush socket pools (https://geekdroids.com/waiting-for-available-socket/#2_Flush_socket_pools)
Flush DNS (https://geekdroids.com/waiting-for-available-socket/#3_Flush_DNS)
We have a GWT based thick client like web application. The application is considerably large and has some initial load time.
We would like to send the users of our application e-mail messages with href links that would open up a specific asset in our application. Well this of course has the effect that clicking the link opens up the application again, reloads it which we would like to avoid. Ideally we would like the href link to just signal our application/web page somehow so that we could pick up the event in our application and react to it.
Any ideas how we should approach this or is this even possible ?
Thanks!
You need to use a GWT Hyperlink which is a widget that serves as an "internal" hyperlink. That is, it is a link to another state of the running application. When clicked, it will create a new history frame using History.newItem(java.lang.String), but without reloading the page.
If you are not already using it, information is here on GWT's History mechanism
There seems not to be any elegant solution to send an event from a link to an existing browser window. Few solutions I have encountered this far:
a) Implement a cookie polling solution for the application to poll if a cookie exists or changes. The link points to our server which just sets the cookie and this way informs the running app about the event. Some tricky handling should be implemented with some kind of 2-way protocol between the returned temporary page from server to handle the situation where the application is not (yet) running.
b) The same approach as in solution a) but use html5 local storage for communication. This way the poller is not needed as the local storage fires an event when content changes. This would be a possible solution but is not for me as we have to support older browsers without local storage support.
c) A long polling ajax or a web socket for delivering events from the server to the client. A solution but seems overkill and might require a modern browser for atleast web sockets.
After many support cases we are realizing the biggest problem we have with our GWT-based application is that users are leaving it open for weeks at a time. This means when we do a hotfix every week or two the RPC stubs are out of sync and cause silent exceptions to be thrown making the site look "broken". Does anybody know of a way to auto-detect and avoid this issue? A few ideas I have had are...
On catching an RPC mismatch exception refresh the browser.
When loading the host page inject the version number in source control the build came from, have a status checker/timer that check that the number did not change. When it does reload.
Reload on an arbitrary timer (perhaps twice daily).
Any ideas?
I'd like to present a fourth option.
Create an RPC Proxy and UI Object proxy that all UI requests and RPC requests are routed through. This way whenever this proxy detects that something is out of date it can dynamically load the widget or change it's expected RPC models.
This is pretty how Vaadin does things and it works great. Vaadin is a UI toolkit built on GWT in case you're not aware. We have several long running production applications using this over the last couple of years and we have made some tweaks in their UI Def language (UIDL) to add version mismatch.
This diagram is a good representation of what they do and if you don't want to build something like this yourself I'd of course recommend moving to Vaadin.
Implement security that logs users out after an hour of idle time. Assuming your releases are overnight or on weekends, the users are logging in after the release. No need to refresh the app.
this is viable especially if your site eventually needs users to login.
I'm working on an iPhone application that should work in offline and online modes.
In it's online mode it's supposed to feed all the information the user enters to a webservice backed by GWT/GAE.
In it's offline mode it's supposed to store the information locally, and when connection is available sync it up to the web service.
Currently my plan is as follows:
Provide a connection between an app and a webservice using Protobuffers for efficient over-the-wire communication
Work with local DB using Core Data
Poll the network status, and when available sync the database and keep some sort of local-db-to-remote-db key synchronization.
The question is - am I in the right direction? Are the standard patterns for implementing this? Maybe someone can point me to an open-source application that works in a similar fashion?
I am really new to iPhone coding, and would be very glad to hear any suggestions.
Thanks
I think you've blurring the questions together.
If you've got a question about making a GWT web interface, that's one question.
Questions about how to sync an iPhone to a web service are a different question. For that, you don't want to use GWT's RPCs for syncing, as you'd have to fake out the 'browser-side' of the serialization system in your iPhone code, which GWT normally provides for you.
about system design direction:
First if there is no REAL need do not create 2 different apps one GWT and other iPhone
create one but well written GWT app. It will work off line no problem and will manage your data using HTML feature -- offline application cache
If it a must to create 2 separate apps
than at least save yourself effort and do not write server twice as if you go with standard GWT aproach you will almost sertanly fail to talk to server from stand alone app (it is zipped JSON over HTTP with some tricky headers...) or will write things twise so look in to the RestLet library it well supported by the GAE.
About the way to keep sync with offline / online switching:
There are several aproaches to consider and all of them are not perfect. So when you conseder yours think of what youser expects... Do not be Microsoft Word do not try to outsmart the user.
If there at least one scenario in the use cases that demand user intervention to merge changes (And there will be - take it to the bank) - than you will have implement UI for this - than there is a good reason to use it often - user will get used to it. it better than it will see it in a while since he started to use the app because a need fro it is rare because you implemented a super duper merging logic that asks user only in very special cases... Don't do it.
balance the effort. Because the mess that a bug in such code will introduce to user is much more painful than the benefit all together.
so the HOW:
The one way is the Do-UnDo way.
While off line - keep the log of actions user did on data in timed order user did them
as soon as you connected - send to server and execute them. Same from server to client.
Will work fine in most cases as long as you are not writing a Photoshop kind of software with huge amounts of data per operation. Also referred as Action Pattern by the GangOfFour.
Another way is a source control way. - Versions and may be even locks. very application dependent. DBMS internally some times use it for transactions implementations.
And there is always an option to be Read Only when Ofline :-)
Wonder if you have considered using a Sync Framework to manage the synchronization. If that interests you can take a look at the open source project, OpenMobster's Sync service. You can do the following sync operations
two-way
one-way client
one-way device
bootup
Besides that, all modifications are automatically tracked and synced with the Cloud. You can have your app offline when network connection is down. It will track any changes and automatically in the background synchronize it with the cloud when the connection returns. It also provides synchronization like iCloud across multiple devices
Also, modifications in the Cloud are synched using Push notifications, so the data is always current even if it is stored locally.
Here is a link to the open source project: http://openmobster.googlecode.com
Here is a link to iPhone App Sync: http://code.google.com/p/openmobster/wiki/iPhoneSyncApp
Can anyone tell me How does the Sync Button on many Iphone app. works (like 'Le Monde').
The button download and replace all files of the application? only look for change (new entry) on the database and add them?....
Thanks,
Typically a button like that is making a web service call, depending on the call you may be updating or replacing the information currently on the device.
Some web services will allow you to ask for information since a certain date:
/FetchArticles?afterDate=200911011952
Some will just provide you with a set amount of information.
Most of the time the calls to a web service will return light enough data that you can just replace what you had with what you fetch, but sometimes the data is a little heavier(images, video, etc...), so you'll want to hang onto what you already have and add to it.
Without knowing more about your App, or if it even uses network resources it's hard to provide any more help.