Cacher

It does the hard work so you don't have to!

What is it?

HTTP Caching implemented as express middleware, with pluggable backends for support for a variety of caching servers (memcached, redis, etc)

Features

• Set expiry times per-app or per-route. It sets proper headers for client caching
• Avoids the thundering heard by smartly refreshing the cache
• Emits hit or miss events so you can track your hitrate
• Simple invalidations
• Overrides for custom cache keys and dev mode support
• Obeys (some) client Cache-Control headers

What does it look like?

varCacher=require("cacher")// use the default in memory cachevarcacher=newCacher()// or pass in a different cache client (in this cached memcached) for different backend supportCacherMemcached=require('cacher-memcached')varcacher=newCacher(newCacherMemcached('host1:12345'))// as a global middlewareapp.use(cacher.cache('seconds',30))// or per routeapp.get("/long-cache",cacher.cache('days'), ...)app.get("/short-cache",cacher.cache('minute'), ...)// will set no-cache headers for routes that we explicitly want to ignore caching onapp.get("/no-cache",cacher.cache(false), ...)// Backwards compatible with old cache definitionsapp.use(cacher.cacheHourly())app.get("/long-cache",cacher.cacheDays(2), ...)// invalidation supportcacher.invalidate('/home')// listen for events to track cache rate and errorscacher.on("hit",function(key){console.log("woohoo!")})cacher.on("miss",function(key){console.log("doh!")})cacher.on("error",function(err){console.log(err)})// Dev mode, quickly turn off caching when it gets in the wayapp.configure('development',function(){cacher.noCaching=true})// override cache key generation for finer grain controlcacher.genCacheKey=function(req){returnreq.path+req.header('user-agent')}// override cache TTL based on responsecacher.genCacheTtl=function(res,origTtl){if(res.statusCode>=400){return0}returnorigTtl}

Backends

Currently, Cacher comes bundled with an in-memory cache

Backends are distributed as separate modules:

• cacher-memcached (https://github.com/addisonj/cacher-memcached)
• cacher-redis (https://github.com/addisonj/cacher-redis)

Backend Client Api

If you want to implement your own backend, the API is really simple:

// pass whatever options are needed for connection/options// provide defaults so a client can be fully instantiated with no parametersfunctionMyBackend(...){}// cb is required, cb(err, cacheObject)MyBackend.prototype.get=function(key,cb){}MyBackend.prototype.set=function(key,cacheObject,ttlInSeconds,[cb]){}MyBackend.prototype.invalidate=function(key,[cb]){}

Testing your backend

Run unit tests using your backend by doing the following:

cd Cacher
npm link ../myBackend
CACHER_CLIENT=myBackend npm test