ie save onunload bug

Question

I have a dynamic ajaxy app, and I save the state when the user closes the explorer window. It works ok in all browsers but in IE there is problem. After I close twice the application tab, i can't connect anymore to the server.

My theory is that the connection to the server fail to complete while the tab is being closed and somehow ie7 thinks that it has 2 outstanding connections to the server and therefore queues new connections indefinitely.

Any one has experienced this, any workaround or solution?

Answer 1

Well, you can get around the connection-limit easily enough; simply create a wildcard domain and instruct your app to round-robin the subdomains; e.g. a.rsrc.dmvnoc.com, b.rsrc.dmvnoc.com, etc, for my netMail application. Without this trick, preloading all the images takes almost 30 seconds on a LAN (because of MSIE's low connection limit), but with it, the images download in about a second.

If you need to combine scripts with this trick, just set document.domain to the parent in the new scripts.

However, you might want to checkpoint the state on change anyway- the user might lose their network connection, or their computer might crash. If you want to reduce network traffic, have the client simply set a cookie that contains the relevent state- you can fit an awful lot in there (3000 bytes or so) and then the server gets it automatically on the next connection anyway- where it can save the results (as it presently does) and remove the cookie to signal that it has saved the state.

Answer 2

In IE if you use long-polling AJAX request, you have to close down the XHR connection on 'unload'. Otherwise it will be kept alive by browser, even if you navigate away from your site. These kept alive connections will then cause the hang, because your browser will hit the maximum open connection limit.

This problem does not happen in other browsers.