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

Current Tags

• 1.1.0                                ...           latest (9 years ago)

7 Versions

• 1.1.0                                ...           9 years ago
• 1.0.5                                ...           10 years ago
• 1.0.4                                ...           10 years ago
• 1.0.3                                ...           11 years ago
• 1.0.2                                ...           11 years ago
• 1.0.1                                ...           13 years ago
• 1.0.0                                ...           14 years ago