Package Exports

semaphore

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (semaphore) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

semaphore.js

Install: npm install semaphore

Limit simultaneous access to a resource.

// Create
var sem = require('semaphore')(capacity);

// Take
sem.take(fn[, n=1])
sem.take(n, fn)

// Leave
sem.leave([n])

// Available
sem.available([n])

// Limit concurrent db access
var sem = require('semaphore')(1);
var server = require('http').createServer(req, res) {
    sem.take(function() {
        expensive_database_operation(function(err, res) {
            sem.leave();

            if (err) return res.end("Error");

            return res.end(res);
        });
    });
});

// 2 clients at a time
var sem = require('semaphore')(2);
var server = require('http').createServer(req, res) {
    res.write("Then good day, madam!");

    sem.take(function() {
        res.end("We hope to see you soon for tea.");
        sem.leave();
    });
});

// Rate limit
var sem = require('semaphore')(10);
var server = require('http').createServer(req, res) {
    sem.take(function() {
        res.end(".");
        
        setTimeout(sem.leave, 500)
    });
});

License

MIT