A simple way to limit how often a function is executed.
If you want to limit all requests:
var limit = require("simple-rate-limiter");
var request = limit(require("request")).to(10).per(1000);
userIds.forEach(function(userId) {
var url = "http://easily-overwhelmed-api.com/users/" + userId;
request(url, function(err, res, body) {
/* ... Yay! Not a too-many-request-per-second error! ... */
});
})
Or if you'd like to be a bit more fine grain and/or explicit:
var limit = require("simple-rate-limiter");
var callApi = limit(function(userId, callback) {
var url = "http://easily-overwhelmed-api.com/users/" + userId;
request(url, callback);
}).to(10).per(1000);
userIds.forEach(function(userId) {
callApi(userId, function(err, res, body) {
/* ... Yay! Not a too-many-request-per-second error! ... */
});
})
Basic usage: let limited = limit(fn)
limited(args...)
: Enqueues a set of arguments that fn
will be executed with. Returns an EventEmitter that will emit a limiter-exec
event when fn
is executed with args
. Also, in the case that fn
returns an EventEmitter, the events emmitted by the returned EventEmitter will be relayed to the EventEmitter returned by limited
. In other words, stuff like this works:
var limit = require("simple-rate-limiter");
var request = require("request");
limit(request)("http://google.com").on("data", function(chunk) { /*** code ***/ });
limited.to(count=1)
: The number of times fn
will be execute within the time specified by .per(time)
.
limited.per(time=Infinity)
: The number of milliseconds in which fn
will be executed .to(count)
number of times.
limited.evenly([toggle=true])
: Off by default. When true, fn
will be executed evenly through the time period specified by .per(time)
. For example, if set to true and .to(10)
and .per(1000)
, then fn
will be executed every 100ms.
limited.withFuzz([percent=0.1])
: Set to 0 by default. Adds a random factor to the delay time. For example if set to 0.1 and .to(10)
and .per(1000)
, then fn
will be executed between every 100ms to 110ms.
limited.maxQueueLength(max)
: Set to 5,000 by default. If more than 5,000 pending actions are queued, then an exception will be thrown.
All methods attached to limited
and can be chained.
Context for a function can be set with limit(fn, ctx)
or limit.promise(promiser, ctx)
.
Simple rate limiter supports promises with limit.promise
. Limited promises have support the same chainable methods as limit
. Example usage:
const limited = limit(getUser).to(10).per(1000);
const users = await Promise.all(userIds.map(id => limited(id)));
/* ... Yay, I didn't spam anyone! ... */
limit.promise(promiser[, ctx])
: Returns a promise. Calls the promises
no more often than the to
and per
fields dictate. An optional context parameter can be passed in.Basic usage: limit(fn).to(count).per(interval)
The to
method or per
can be called any number of times including zero. The effective default count for to
is 1 and the effective default interval for per
is Infinity. Which means if neither the to
method or per
method are called, then limit
will only execute fn
once ever:
var init = limit(function() { console.log("Runs only once"); });
for(var i = 0; i < 3; i++) { init(); }
/*** Console output: ***/
// $ Runs only once
// ... Nothing else is ever printed ...
Similarly, if per
is never called, fn
is executed at most count
number of times:
var dos = limit(function() { console.log("twice only"); }).to(2);
for(var i = 0; i < 3; i++) { dos(); }
/*** Console output: ***/
// $ twice only
// $ twice only
// ... Nothing else is ever printed ...
On the other hand, if to
is never called, fn
is only executed every interval
milliseconds:
var tick = limit(function() { console.log("Once a second..."); }).per(1000);
for(var i = 0; i < 3; i++) { tick(); }
/*** Console output: ***/
// $ Once a second
// ... pause for 1 second ...
// $ Once a second
// ... pause for 1 second ...
// $ Once a second
Finally, as mentioned earlier, to
and per
can be called any number of times. Each time either to
or per
is called, the previous count
or interval
value is overriden:
var strange = limit(function() {
console.log("Every once in a while");
}).to(1).per(1000).to(2).per(2000);
for(var i = 0; i < 3; i++) { strange(); }
/*** Console output: ***/
// $ Every once in a while
// $ Every once in a while
// ... pause for 2 second ...
// $ Every once in a while
The easiest way to get simple-rate-limiter is with npm:
npm install simple-rate-limiter
Alternatively you can clone this git repository:
git clone git://github.com/xavi-/node-simple-rate-limiter.git
This project is released under The MIT License.