Website load distribution using Javascript

My music search engine shows a list of songs as you type — sort of like Google’s autosuggest feature. I load my entire list of songs upfront for this to work. Though it’s compressed to load fast, each time you load the page, it downloads about 500KB worth of song titles.

My allotted bandwidth on my hosting service is 3GB per month. To ensure I don’t exceed it, I uploaded the songs list to an alternate free server: Freehostia. This keeps my load down. If I exceed Freehostia’s limit, my main site won’t be affected — just the songs. I also uploaded half of them to Google Pages, to be safe.

This all worked fine… until recently. Google Pages has a relatively low bandwidth restriction. (Not sure what, and they won’t reveal it, but my site is affected.) Freehostia is doing some maintenance, and their site goes down relatively often. So my song search goes down when any of these go down.

Now, these are rarely down simultaneously. Just one or the other. But whenever Freehostia is down, I can’t listen to one bunch of songs. When Google Pages is down, I can’t listen to another.

What I needed was a load distribution set-up. So I’ve made one in JavaScript.

Normally, I load the song list using an external javascript. I have a line that says:

<script src="http://sanand.freehostia.com/songs/..."></script>

… and the song’s loaded from Freehostia.

What I’d like to do is:

loadscripts(
    "list.hasLoaded()", [
    "http://sanand.freehostia.com/songs/...",
    "http://root.node.googlepages.com/...",
    "http://www.s-anand.net/songs/..."
])

If the function can’t load it from the first link, it loads it from the second, and so on, until list.hasLoaded() returns true.

Here’s how I’ve implemented the function:

function loadscripts(check, libs) {
    document.write('<script src="' + libs.shift() +
        '"><' + '/script>');

    if (libs.length>0) document.write('<script>if (!(' + check + ')) {'
        + 'loadscripts("' + check + '",["' + libs.join('","')+'"])'
        + '}</' + 'script>')
}

The first document.write loads the first script in the list. The if condition checks if there’s more scripts to load. If yes, the second document.write writes a script that

• checks whether the script is already loaded, and
• if not, loads the rest of the scripts using the same function.

I’ve expanded the sites that have these free songs as well. So now, as long as my main site works, and at least one of the other sites work, the search engine will work.

PS: You can easily expand this to do random load distribution as well.