api-client-limiter

API Client Limiter

Some web API limits the number of calls you can make in a certain period of time. After looking for a node module that just do that, I was frustrated and created mine. All modules I saw were either very complex to use or were actually "debouncing" or throttling calls, which means that all calls within a certain time frame get the same results instead of doing the full round trip to the API.

This simple module does only one thing: it wraps a function following the standard nodejs callback pattern, queue calls and execute the real method every X seconds.

Installing

Just install the module in your node project using the following call :

npm install api-client-limiter

Limiting your API calls

Here's a quick sample on how to transform a tight loop performing API calls into a limited one. This sample use async to control the loop, because of the provided callback parameter. This is the ideal way of using this module.

var Limiter = require('api-client-limiter');

// Create a limiter for 1 call every 2 seconds
var limiter = new Limiter(1, 2000);

// Wrap a callback that will be called for a team collection
var callback = limiter(function(team, done) {

    console.log("This will be queued and called every 2 seconds");

    // An API call is performed by this callback
    request.get({
        url: 'http://api.sample.com',
        json:true,
        agent:false
    }, function(err, resp, body) {
        // Let's do anything with the received data...
        db.save(body);
        done();
    });

});

async.forEach(teams, callback, function(err) {
    console.log("Execution is now complete. All teams have been processed");
});

Like your can see in this sample, calling limiter with the function your want to limit is very easy. Internally, we create a queue allowing a certain number of parallel calls every x milliseconds. Each call to limiter will enqueue a call to your original callback, wrapped in a timer of the given duration.

Limitations

For now, only functions with a callback as the last parameter are supported. I may add support for promises in the future, but for now, that was what I needed for my use case.