proxy.pac file performance optimization

Question

I reroute certain websites through a proxy with a proxy.pac file.

It basically looks like this:

if (shExpMatch(host, "www.youtube.com"))
    { return "PROXY proxy.domain.tld:8080; DIRECT" }
if (shExpMatch(host, "youtube.com"))
    { return "PROXY proxy.domain.tld:8080; DIRECT" }

At the moment about 125 sites are rerouted using this method. However, I plan on adding quite a few more domains to it, and I'm guessing it will eventually be a list of 500-1000 domains.

It's important to not reroute all traffic through the proxy.

What's the best way to keep this file optimized, performance-wise ?

Thanks

Answer 1

As usual: hashes or trees.

I'd use hashing: extract the first one (or more chars) of the requested domain name (stripping "www." as well) to select corresponding pattern list.

Answer 2

If you are just checking for equality use '==' for comparison. The shExpMatch function allows for shell expressions (* and ? in their DOS shell meanings) so the second argument has to be parsed. The script runs in the browser, once (or less) per request so performance is not an issue but it makes the code clearer if you write what yuo mean.

I would also use a variable to hold the proxy expression. It probably won't save run-time storage as the repeated literal is probably re-used, but it will make the code easier to read.

There is good info on http://www.proxypacfiles.com/ including examples and lessons learned.