Cold FeetUser Guide

Overview

Cold Feet is an asset caching strategy for your Bed App.

Tired of telling clients to clear their browser cache to pick up the latest CSS and Javascript changes?
Don't want lame browser cache busting because you need network performance?
Then get Cold Feet!

Install

Install Cold Feet with the Fantom Repository Manager ( fanr ):

$ fanr install -r http://repo.status302.com/fanr/ afColdFeet

To use in a Fantom project, add a dependency to build.fan:

depends = ["sys 1.0", ..., "afColdFeet 0+"]

Usage

Contribute your asset directories to the BedSheet FileHandler service as usual, but rather than hard-coding the asset URIs, let Cold Feet generate them for you.

Use the ColdFeet service to convert your asset URIs, such as /css/myStyles.css, to a Cold Feet URI like /coldFeet/XXXX/css/myStyles.css, where:

/coldFeet is a prefix used to identify the URI on incoming requests.
/XXXX is a checksum, generated by Cold Feet, that changes when the asset content changes.

When a request is made for the asset using the modified URI, Cold Feet intercepts the request using BedSheet middleware and serves up the file. Cold Feet lets the browser aggressively cache it by setting a far-future expiration header (10 years by default).

If during those 10 years the asset is modified then the Cold Feet URI will change, as the XXXX checksum will be updated. This forces the browser to download the new asset.

The smart ones amongst you will be asking, "But what if the browser requests an old asset URI?" Simple, Cold Feet recognises outdated URIs and responds with a 301 - Moved Permanently redirecting the browser to the new asset URI.

Checksum Strategies

App Version

This simple strategy (currently the default) actually ignores the asset file in question and instead returns the application's pod version. Thus, when a new application is deployed (with an new version), clients will re-download all the assets.

When not in production mode, the checksum defaults to a random string and the expiration header is disabled.

Const Value

Use this strategy in testing. It returns a set constant value each and every time. To use, override the default App Version implementation in your AppModule:

class AppModule {
    @Contribute { serviceType=ServiceOverride# }
    static Void contributeOverrides(MappedConfig config) {
        config[ChecksumStrategy#] = ChecksumFromConstValue("XXX")
    }
}