Tan Nguyen Tan Nguyen - 5 months ago 122
Node.js Question

Nodejs Express framework caching

I am using Nodejs and Express Js. Also I add NowJS to the Express Js to do some real-time stuffs.

In the configuration file I have

app.configure('production', function() {
var oneYear = 31557600000;
app.use(express.static(__dirname + '/public', { maxAge: oneYear }));
app.use(express.errorHandler());});


And I run the application using this command:

$ NODE_ENV=production node app.js


However, the files(images, css, js) seem not to be cached, they are always served as new file.

P/s: I have just tested it with localhost, the cache seems to work on localhost, however, when uploading to the server, the cache is not working anymore.

Answer Source

Express is built on Connect, and Connect provides the "static" middleware. Here's the code under the hood for the caching:

if (!res.getHeader('Cache-Control')) res.setHeader('Cache-Control', 'public, max-age=' + (maxAge / 1000));

You can find that code here:

https://github.com/senchalabs/connect/blob/master/lib/middleware/static.js#L147

So as you can see Express is sending a "Cache-Control" header to the browser, telling him to cache that file for a period. So this isn't a "load a file once and then always serve it to all clients", but more of a "tell each client to cache the file the first time he downloads it" (which means all the clients will have to download that file once before it's cached for them).

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