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Add X-RateLimit-* headers according to industry standards #43

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22 changes: 20 additions & 2 deletions lib/middleware.js
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Original file line number Diff line number Diff line change
@@ -1,4 +1,6 @@
var rateLimiter = require('./rate-limiter');
var rateLimiter = require('./rate-limiter');

var defaultFailMessage = 'Rate limit exceeded, retry after {after}ms';

module.exports = function(opts) {
var limiter = rateLimiter(opts);
Expand All @@ -7,8 +9,24 @@ module.exports = function(opts) {
if (err) {
next();
} else {
res.set({
'X-RateLimit-Limit': rate.limit,
'X-RateLimit-Remaining': rate.current > rate.limit ? 0 : rate.limit - rate.current,
'X-RateLimit-Reset': (rate.reset / 1000) | 0
});
if (rate.current > rate.limit) {
res.writeHead(429);
var after = rate.reset - Date.now();
var failMessage = defaultFailMessage;
res.set('Retry-After', (after / 1000) | 0);
if(opts.failMessage) {
if(typeof opts.failMessage === 'function') {
failMessage = opts.failMessage(req);
}
else {
failMessage = opts.failMessage;
}
}
res.status(429).send(failMessage.replace(/{after}/g, after));
res.end();
} else {
next();
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14 changes: 10 additions & 4 deletions lib/rate-limiter.js
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Original file line number Diff line number Diff line change
Expand Up @@ -10,21 +10,27 @@ module.exports = function(opts) {
.setex(tempKey, opts.window(), 0)
.renamenx(tempKey, realKey)
.incr(realKey)
.ttl(realKey)
.pttl(realKey)
.exec(function(err, results) {
if(err) {
callback(err);
} else {
if (results[3] == -1) { // automatically recover from possible race condition
opts.redis.expire(realKey,opts.window());
var reset, ttl = results[3];
if(ttl == -1) { // automatically recover from possible race condition
opts.redis.expire(realKey, opts.window());
reset = Date.now() + opts.window() * 1000;
}
else {
reset = Date.now() + ttl;
}
var current = results[2];
callback(null, {
key: key,
current: current,
limit: opts.limit(),
window: opts.window(),
over: (current > opts.limit())
over: (current > opts.limit()),
reset: reset
});
}
});
Expand Down