connect-appcache-proxy

A proxy for files listed in an HTML5 appcache manifest.

Why?

When a website is served over SSL, loading resources from a different domain into the appcache is not allowed, even if these resources are served over SSL.

If you want to be able to deploy static assets quickly via Amazon S3 or similar, while still being able to use HTML5 Appcache and SSL at the same time, this module might come in handy.

Usage

var connect = require("connect")
var AppcacheProxy = require("connect-appcache-proxy")
 
var app = connect()
app.use(new AppcacheProxy("http://youraccount.staticfilehost.com/appcache.manifest"))

Refreshing the cache

You can call proxy.refresh(cb) to refetch the manifest and repopulate the cache from its source at any time. The new cache will be activated as soon as its entirely ready, ensuring the set of resources served are of the same release.

var app = connect()
var proxy = new AppcacheProxy("https://secure.staticfileserver.com/youraccount/appcache.manifest")
app.use(proxy))
proxy.refresh (function(err) {
  if (err) {
    console.error("Appcache proxy failed to initialize.")
    console.error(err)
    // perhaps use some retry strategy
  }
  else console.log("Appcache proxy is ready.")
})

Options

You may pass the AppCacheProxy constructor an options object as second argument. Possible options are:

• log - a log function. Defaults to a noop. Can be handy to see what's going on.
• overrideEntries - an object with key-value pairs with key the cache entry you want to override, and value the url you want to override it with. This is handy when you want to put /, ./ or similar entries into your manifest but your static file host does not allow specifying a resource for such an url.
• callback - if autostart is true, this is called when the cache has finished initializing. Only at this moment is your server ready to serve requests for the files in the manifest. Defaults to throwing an error, if any.
• autostart - will automatically populate the cache when the constructor is called. Defaults to true.
• allowHeaders - the headers that are copied verbatim from the response received from the static file host. Defaults to ["cache-control", "content-type", "content-encoding", "content-length", "last-modified"]
• busyMessage - when showBusy is true, then you may specify the text/plain content that is served. Defaults to "The server is restarting. Try again in a minute."
• showBusy - when the cache is being populated, there's a brief time in which your server is not able to serve requests. This only happens once on server startup. If set to true, then a 503: Server is busy response will be served. If set to false, then any request is simply passed on to the next middleware. This in turn would most likely return in a 404 in the end, unless you serversome kind of fallback resources elsewhere.

Credits

The initial structure of this module was generated by Jumpstart, using the Jumpstart Black Coffee template.

License

connect-appcache-proxy is released under the MIT License.
Copyright (c) 2013 Meryn Stol