mutex

Distributed mutex for nodejs with redis backend

npm install mutex
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Warning

This lib was written for big full-stack JS project tactoom.com in 2011 and still works successfully on production.

But I want to warn you, this lib is very old and was highly tested only for node 0.4.x (and with other old shit). It is also proven by using only in one project, so there's no any guarantees at all.

I do not suggest you to use it for something vital.

Mutex.lock(key, lifetime, callback) / Mutex.free(key, callback)

// Initialize mutex object
var Mutex = require('mutex');
var mutex = new Mutex();

// Acquire 'foo' for 10 secods (maximum)
mutex.lock('foo', 10000, function(err, locked, ttl){
    if (locked) {
        // do something with 'foo' ...

        // free 'foo'
        mutex.free('foo');
    }
    else {
        // 'foo' is locked at the moment
    }
})

Mutex.isolate(key, lifetime, fn, callback)

// Acquire 'foo' for 10 secods (maximum)
mutex.isolate('foo', 10000, function isolated(callback){

    // do something with 'foo' ...

    // 'foo' will be freed atomatically
    callback(null, 'some result');

}, function after(err, result) {

    // failed to acquire 'foo'
    if (result === false) {

    }
    // 'foo' was acquired and processed
    else {
        console.log(result); // 'some result'
    }

})

Mutex.isolateRetry(key, lifetime, fn, callback)

Same as isolate() but it will retry to lock again and again until it will be freed.

// Acquire 'foo' for 10 secods (maximum)
mutex.isolateRetry('foo', 10000, function isolated(callback){

    // do something with 'foo' ...

    // 'foo' will be freed atomatically
    callback(null, 'some result');

}, function after(err, result) {

    console.log(result); // 'some result'
})

Mutex.isolateCondRetry(key, lifetime, checkFn, fn, callback)

Conditional isolation. If checkFn() returns 'mutex.continue' it will isolate, else it will not lock.

var a = true; // or 'false'

// Acquire 'foo' for 10 secods (maximum)
mutex.isolateCondRetry('foo', 10000, function check(callback) {

    // If some condition
    if (a) {
        // We need to isolate
        callback(null, mutex.continue);
    }
    else {
        callback(null, 'cached')
    }

}, function isolated(callback){

    // do something with 'foo' ...

    // 'foo' will be freed atomatically
    callback(null, 'some result');

}, function after(err, result) {

    // if a == true --> 'some result'
    // if a == false --> 'cached'
    console.log(result); 
})

Installation

$ npm install mutex
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