Improve performance

[annam002]

Performance has been reported to be poor sometimes, especially in Firefox. Analyse the possible sources of performance problems and eliminate them.

[annam002]

Possible performance culprits

• Too many unnecessary server calls - loading and re-loading should be optimized
• Loading more js than necessary (e.g., why does impressum.html need talklist.js and ui.js? Seems the code separation is wrong)
• Inefficient local storage - maybe store processed data in indexed db/local cache instead of raw server data
• Inefficient use of knockoutjs-listeners (e.g., for every talk, a listener is registered to update the models when the language changes; one listener for all seems more useful)
• Unminimized js (could possibly be minimized when running maven install)

[annam002]

Optimize loading

The data should only be loaded from the server when necessary. Currently, I implemented a timeout - the data is valid for two hours. After that, the data is reloaded from the server and the timeout is reset. This is still suboptimal:

• If the data changes on the server, we only get the changes after two hours. It should be possible to ask the server if there is new data. Created https://github.com/dukecon/dukecon_server/issues/30
• When the user is offline and the timeout has run out, the app becomes slow again, because it tries to contact the server everytime. It should be possible to check for offline state.

[annam002]

Offline detection

It is difficult to detect the online/offline state of the browser. There is an API in HTML 5 for this, but it is not consistently implemented across browsers. The safest bet seems to be to listen for the status of the appcache file load and set an offline flag when the appcache file cannot be loaded: http://www.html5rocks.com/en/mobile/workingoffthegrid/#toc-appcache

I implemented this, but unfortunately, the offline flag can only be set after the page is already loaded. Therefore, I store the offline state in the local cache, so that from the second time the app is loaded in offline state, it does not try to connect to the server.This also means that when the app goes online again, the app is in offline state on the first load. If we had https://github.com/dukecon/dukecon_server/issues/30 implemented, it could be an idea to check for data refreshes at this point and reload the page.

[annam002]

Implemented a regular check for server updates based on the newly built etag-hash-information.

[annam002]

With the actionstaken, performance seems to be a lot better, so closing the issue for now.