express-view-cache

Unobtrusive solution to express 4.0.0 framework - cache response content in Redis database.

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Why do we need this plugin and how does it work?

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 rendering 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 received, 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 ran 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 is turned that it works best with node-redis with redis >v2.6.16

Example

There is a complete example of NodeJS + ExpressJS (4.x.x) application which responds with current time.

'use strict';

const express = require('express');
const  morgan = require('morgan');
const  errorHandler = require('errorhandler');
const  request = require('request');
const  http = require('http');
const  EVC = require('./../');
const  app = express();
const  evc = EVC('redis://redis:someLongAuthPassword@localhost:6379');

app.set('port', process.env.PORT || 3000);
app.use(morgan('dev'));

// simple caching middlewared
app.use('/cacheFor5sec', evc.cachingMiddleware(5000)); // every path with prefix /cacheFor5sec is cached for 5 seconds
app.use('/cacheFor3sec', evc.cachingMiddleware(3000)); // every path with prefix /cacheFor3sec is cached for 3 seconds

// every path with /cacheCustom will be cached with key based on users IP  and ttl 3 seconds
app.use('/cacheCustom', evc.customCachingMiddleware(function (req, cb){
  return process.nextTick(function (){
    cb(null, `${req.ip}`, 3000);
  });
}));

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

http.createServer(app).listen(app.get('port'), function () {
  console.log('Express server listening on port %s', app.get('port')); // eslint-disable-line
  setInterval(function(){
    request('http://localhost:'+app.get('port')+'/', function(error, response, body){
      console.log('GET /',body);  // eslint-disable-line
    });
  }, 1000);
  setInterval(function(){
    request('http://localhost:'+app.get('port')+'/cacheFor3sec', function(error, response, body){
      console.log('GET /cacheFor3sec',body);  // eslint-disable-line
    });
  }, 1000);
  setInterval(function(){
    request('http://localhost:'+app.get('port')+'/cacheCustom', function(error, response, body){
      console.log('GET /cacheCustom',body);  // eslint-disable-line
    });
  }, 1000);
});

Options

const evc = EVC(options);

Options can be a redis connection string like redis://usernameTotallyIgnored:someLongPassword@redis.example.org:6379

also options can be a dictionary object with these fields:

• host - default is localhost - the hostname of redis server
• port - default is 6379 - the port where the redis server listens
• pass - password for redis authorization, default is null
• client - ready to use node-redis client - this option overrides all previous

Using simple caching middleware

This middleware simply caches response for given duration with req.originalUrl as caching key:

app.use('/pathPrefixToBeCachedForFiveSeconds', evc.cachingMiddleware(5000));

Using custom caching middleware

This middleware accepts async function that extracts key name and ttl from request object. It can be used for writing complicated caching rules, for example, these ones:

// every path with /cacheCustom will be cached with key based on users IP  and ttl 3 seconds
app.use('/cacheCustom', evc.customCachingMiddleware(function (req, cb) {
  const key = `${req.ip}`;
  return process.nextTick(function () {
    cb(null, key, 3000);
  });
}));

Consider we have dashboard, that should be cached for 1 second for admin users, and for 5 seconds - to ordinary users. And every user has to have his/her own data.

const dashboardRouter = express.router();
// consider we use PassportJS to reject unauthorized access
dashboardRouter.use(function requireAuthorized(req, res, next) {
  if(req.user) {
    return next();
  }
  return  res.sendStatus(401);
});

// cache dashboard 
dashboardRouter.use('/dashboard', evc.customCachingMiddleware(function (req, cb) {
  const key = `DashBoardForUser${req.user.id}`; // caching key contains useds ID
  const ttl = req.user.admin ? 1000 : 5000; // caching TTL depends on users permissions
  return process.nextTick(function () {
    cb(null, key, ttl);
  });
}));

// actually, generate personal dasboard for user
dashboardRouter.get('/dashboard', function (req,res,next){
  req.model.makeDashboardForUser(req.user, function (error, data){
    if(error) {
      return next(error);
    }
    return res.json(data);
  });
});

Tests

$ npm run lint
$ npm test

License

The MIT License (MIT)

Copyright (c) 2013 Ostroumov Anatolij ostroumov095(at)gmail(dot)com et al.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.