ratelimit-middleware

Rate limit middleware for expressjs

var ratelimit = require('ratelimit-middleware');
var app = express();
 
app.use(ratelimit({
    burst: 10,  // Max 10 concurrent requests (if tokens)
    rate: 0.5  // Steady state: 1 request / 2 seconds
});
 
app.get('/throttled/access', function(req, res, next) {
    ...
});

ratelimit(options)

Creates an API rate limiter that can be plugged into the standard restify request handling pipeline.

This throttle gives you three options on which to throttle: username, IP address and 'X-Forwarded-For'. IP/XFF is a /32 match, so keep that in mind if using it. Username takes the user specified on req.username (which gets automagically set for supported Authorization types; otherwise set it yourself with a filter that runs before this).

In both cases, you can set a burst and a rate (in requests/seconds), as an integer/float. Those really translate to the TokenBucket algorithm, so read up on that (or see the comments above...).

In either case, the top level options burst/rate set a blanket throttling rate, and then you can pass in an overrides object with rates for specific users/IPs. You should use overrides sparingly, as we make a new TokenBucket to track each.

Options

Name	Default	Type	Description
rate	-	Number	Steady state number of requests/second to allow
burst	-	Number	Amount of requests to burst to
ip	true	Boolean	Throttle on /32 (source id)
xff	false	Boolean	Throttle on /32 X-Forwarded-For header
username	false	Boolean	Throttle on req.username
overrides	null	Object	Per "key" overrides
tokensTable	-	Object	Storage engine
maxKeys	10000	Number	Maximum distinct throttling keys to allow at a time

Overrides

{
    burst: 10,
    rate: 0.5,
    ip: true,
    overrides: {
        '192.168.1.1': {
            burst: 0,
            rate: 0    // unlimited
        },
        '192.168.1.192/27': {
            burst: 0,
            rate: 0
        }
      }
   }
}

Handle Ratelimit errors

If a request with exceed the rate limit and cannot be processed, the next middleware will be invoked with an Error argument. The error instance will have a status field with code 429 and a message indicating the user has exceeded their quota You have exceeded your request rate of %s r/s.

You can handle this response by providing error handling middleware in your express app.

var app = express();
 
app.use(ratelimit({ ... });
 
app.use(...);
app.get(...);
 
app.use(function(err, req, res, next) {
   err.status // will be 429 if rate limited
 
   // example way to respond
   // NOTE, you will likely want to hide `err.message` for 5xx errors in production.
   res.status(err.stauts || 500).send(err.message);
});

Prior art

This module is repackaged code from the restify library throttle plugin for use with expressjs

License

MIT

See LICENSE.restify for restify's license.