UI freezes for the duration of NDT test

[critzo]

The NDT test performs an asynchronous callback indicating telling the control protocol that the server is ready to feed the test data back to the client. The NDT test calls for receiving data as fast as possible for 10 seconds. The tight receive loop at line 95 of https://github.com/opentechinstitute/mlab-browser-ext/blob/master/lib/plugins/NDT/S2CTest.js

Because of the restriction on doing XPI from only the main thread, when we are in this tight receive loop, we are blocking the UI. No navigation to other tabs or windows is possible during this time.

One possible workaround woudl be to use an implementation of WebSockets, based on the implementation in this ticket: https://bugzilla.mozilla.org/show_bug.cgi?id=733573#c33

[jgmize]

@critzo based on a later comment in the same bug you referred to, you may be able to use the newer TCPSocket API for this by enabling the dom.mozTCPSocket.enabled pref. Based on my understanding from reading the discussion in the bug and elsewhere, you might be able to use this new API from a web worker-- I haven't been able to find anything to confirm this one way or another, but if you give it a shot I'd be interested in finding out. I'm not sure exactly which versions of Firefox this would work on, but you could test for the API availability and fall back to the current XPCOM method for older versions.

[critzo]

@jgmize Thanks for taking a look at this. @hawkinswnaf @technosopher What do you think about the TCPSocketAPI idea?

[hawkinsw]

Hey @jgmize @critzo and @technosopher :

This definitely seems like a doable thing. The webworker/TCPSocketAPI was proposed to us as a possible workaround and it sounds reasonable. I just haven't had a chance to play around and see how it would work :-(

[collina]

@jgmize The TCPSocket API is Firefox OS only, correct?

[hawkinsw]

It would be Firefox extension only, I think.

[jgmize]

Yes, the TCPSocket API is only enabled by default on Firefox OS, so it cannot be used from a webpage on desktop Firefox, but I figured it may be possible to do from an extension. After doing a little more research I found http://stackoverflow.com/a/26359452/2965637, which indicates that you should be able to create a TCPSocket instance using the following:

var socket = Cc["@mozilla.org/tcp-socket;1"].createInstance(Ci.nsIDOMTCPSocket);

[hawkinsw]

Yup. That is a very familiar looking syntax :-)