express-view-cache

Unobtrusive solution to express framework - cache response content, without database requests and page rendering.

Why do we need this plugin and how do it works?

Let's consider we have a NodeJS application with code like this:

app.get('/getPopularPosts',function(req,res){
    req.model.posts.getPopular(function(err,posts){
        if(err) throw err;
        res.render('posts',{"posts":posts});
    });
});

The method getPopular of posts requires a call to database and executed slowly. Also rendeding the template of posts requires some time. So, maybe we need to cache all this? Ideally, when visitor gets the page with url /getPopularPosts we have to give him info right from cache, without requests to database, parsing data recieved, rendering page and other things we need to do to give him this page. The most expressJS way to do it is to make a separate middleware, that is runned before router middleware, and returns page from cache (if it is present in cache) or pass data to other middlewares, but this caching middleware adds a listener to response, which SAVES rendered response to cache. And for future use, the response is taken from CACHE!

It can use memory storage or (via module memjs) Memcache server or memcachier.com solution as backend. Right now it is tested in production on heroku hosting. Feedback is welcome!

Example

There is a complete example of NodeJS + ExpressJS application which responds with current time.

var express = require('express'),
    http = require('http'),
    path = require('path'),
    cachingMiddleware = require('express-view-cache');

var app = express();

app.configure(function () {
    app.set('port', process.env.PORT || 3000);
    app.use(express.logger('dev'));

    //set up caching BEFORE router middleware - because next() is not fired when we got rendered page from cache
    app.use(cachingMiddleware(1000,{'type':'application/json'}));
    app.use('/cacheFor5sec',cachingMiddleware(5000,{'type':'application/json'}));
    app.use('/cacheFor3sec',cachingMiddleware(3000,{'type':'application/json'}));

    //set up router middleware for application
    app.use(app.router);

    app.use(express.errorHandler());

    app.get('*', function(request,response){
        response.json({
            'Page Created At':new Date().toLocaleTimeString()
        });
    });
});

http.createServer(app).listen(app.get('port'), function () {
    console.log("Express server listening on port " + app.get('port'));
});

Options

app.use(cachingMiddleware(1000,{ //invalidation time, informations is stored in cache for 1000 milliseconds
    'type':'application/json', //type of returned content
    'driver':'memjs'//can be `memjs`,`redis`,`memory`
}));

The variable of driver can be ommited, and the middleware will use build in memory storage. Be advised - the memory storage IS NOT INTENTED TO BE PRODUCTION READY! It is memleaky and not shared in cluster. If the variable of driver equals memjs, the memjs module is used for managed memcache. It works from the box if you ran you app at heroku hosting with Memcachier addon installed. Also it works with locally installed Memcached instances - see https://devcenter.heroku.com/articles/memcachier#node-js for details. If you want to use your private Memcache instance, you can set the process inviroment variables like this

export MEMCACHIER_SERVERS="localhost:11211"
export MEMCACHIER_USERNAME=""
export MEMCACHIER_PASSWORD=""

And set the memcache protocol to binary, i.e. run the memcached like this

$ memcached -v -B binary

If you want to use Redis instance, you can set the driver to redis. If your redis server have not the default settings (localhost:6379 withour password), you can set redis parameters by setting enviroment variable of redisUrl like this:

export redisUrl="redis://username:veryLongAndHardPasswordBecauseRedisHashes50kPasswordsEverySecond@somehost:6378"

The parameter of type is for setting response type for returned content - see http://expressjs.com/api.html#res.type for details.

Tests

Install vows and test as usual

$ npm install vows
$ npm test

Credits

Ostroumov Anatolij

License

The MIT License