On 05/16/2016 06:06 PM, Grant Edwards wrote:
This is not Python specific, though I'm turning to Python to do some experimentation and to try to prototype a solution.Is there any way to limit the number of connections a browser uses to download a web page? Browser writers seems to assume that all https servers are massively parallel server farms with hardware crypto support. So, when a browser wants to load a page that has the main html file, a css file, a javascript library or two, and a few icons and background bitmaps, they browser opens up a half-dozen SSL connections in parallel. That's fine when the server is Facebook's server farm. But when it's a small embedded device running at 40MHz with a single-threaded web server and software crypto, it turns a 2-second page load time into a 15-second page load time. When we first added https support years ago, this wasn't a problem. A browser would open _an_ SSL connection (handshake time around 2 seconds), and then send mutliple HTTP requests over that connection to grab a half-dozen files. Each HTTP request would take a few tens of milliseconds, and life was good. Now that 2-second page load takes up to 10-15 seconds because of all the SSL connection setup overhead involved in handling a half-dozen "parallel" connections. I was _hoping_ there was an HTTP header or HTML meta tag that could be used to smack the browser with a clue bat, but there doesn't seem to be. [Please tell me I'm wrong...] Some browsers used to have a global "max parallel connections" setting that the user could control, but a) that seems to be gone from recent versions of browsers I've looked at, and b) we can't ask customers to change that setting just for the benefit of our devices. So now I'm going to set up a simple Python HTTP server to try some other approaches: 1) Only allow the listening socket to accept 1 connection at a time. 2) Accept the TCP connection, but don't allow the SSL handshaking to start on the "extra" connections. 3) ??? 4) Profits! Any ideas?
Have you considered upgrading the device with a recent CPU ? Or is it completely out of the picture ?
Depending on what you are selling, it may be actually cheaper than spending time trying to make it work.
You could also "externalize" the web service, a 35$ raspberry pi would do it. Of course I do realize that everything I said may not make any sense, we'd need to know a little bit more about the "device". If 35$ double the price, that may not be a good idea.
That being said, your first idea seems also a good lead, have your server refuse more than one connection.
jm -- https://mail.python.org/mailman/listinfo/python-list
