limiter
Provides a generic rate limiter for node.js. Useful for API clients, web
crawling, or other tasks that need to be throttled. Two classes are exposed,
RateLimiter and TokenBucket. TokenBucket provides a lower level interface to
rate limiting with a configurable burst rate and drip rate. RateLimiter sits
on top of the token bucket and adds a restriction on the maximum number of
tokens that can be removed each interval to comply with common API
restrictions like "150 requests per hour maximum".
Installation
Use NPM to install:
npm install limiter
Usage
A simple example allowing 150 requests per hour:
var RateLimiter = require('limiter').RateLimiter;
var limiter = new RateLimiter(150, 'hour');
limiter.removeTokens(1, function(err, remainingRequests) {
callMyRequestSendingFunction(...);
});
Another example allowing one message to be sent every 250ms:
var RateLimiter = require('limiter').RateLimiter;
var limiter = new RateLimiter(1, 250);
limiter.removeTokens(1, function() {
callMyMessageSendingFunction(...);
});
The default behaviour is to wait for the duration of the rate limiting
that’s currently in effect before the callback is fired, but if you
pass in true
as the third parameter, the callback will be fired
immediately with remainingRequests set to -1:
var RateLimiter = require('limiter').RateLimiter;
var limiter = new RateLimiter(150, 'hour', true);
limiter.removeTokens(1, function(err, remainingRequests) {
if (remainingRequests < 0) {
response.writeHead(429, {'Content-Type': 'text/plain;charset=UTF-8'});
response.end('429 Too Many Requests - your IP is being rate limited');
} else {
callMyMessageSendingFunction(...);
}
});
A synchronous method, tryRemoveTokens(), is available in both RateLimiter and TokenBucket. This will return immediately with a boolean value indicating if the token removal was successful.
var RateLimiter = require('limiter').RateLimiter;
var limiter = new RateLimiter(10, 'second');
if (limiter.tryRemoveTokens(5))
console.log('Tokens removed');
else
console.log('No tokens removed');
To get the number of remaining tokens outside the removeTokens
-callback
simply use the getTokensRemaining
-method.
var RateLimiter = require('limiter').RateLimiter;
var limiter = new RateLimiter(1, 250);
limiter.getTokensRemaining();
Using the token bucket directly to throttle at the byte level:
var BURST_RATE = 1024 * 1024 * 150;
var FILL_RATE = 1024 * 1024 * 50;
var TokenBucket = require('limiter').TokenBucket;
var bucket = new TokenBucket(BURST_RATE, FILL_RATE, 'second', null);
bucket.removeTokens(myData.byteLength, function() {
sendMyData(myData);
});
Additional Notes
Both the token bucket and rate limiter should be used with a message queue or
some way of preventing multiple simultaneous calls to removeTokens().
Otherwise, earlier messages may get held up for long periods of time if more
recent messages are continually draining the token bucket. This can lead to
out of order messages or the appearance of "lost" messages under heavy load.
License
(The MIT License)
Copyright (c) 2013 John Hurliman. <jhurliman@jhurliman.org>
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.