锁的基本逻辑——互斥

Question

我正在为互斥锁的逻辑而苦苦挣扎；在这里我检查密钥是否被占用，如果没有，我们会拿到它，完成后释放它；但是你能帮我如何让我有一个循环来检查密钥直到它可用吗？

rdb.setnx(lockkey, 'taken', function (err, lockvalue) {
    if (err) {
        console.error(err);
    } else if (lockvalue == 1) {
        // You have the lock; process it
        //Release the key when you are done:
        rdb.del(lockkey);
    } else if (lockvalue == 0) {
        // Key is taken by someone else; so how can I have a loop to check until key is available to take? 
    }
});

感谢您的帮助 :-)

更新：

非常感谢 Adeneco 的回答；我一直对自执行功能的逻辑感到困惑；所以如果我想通过超时，请确认我的逻辑是正确的：

n=1;
(function rec(n) {
    rdb.setnx(lockkey, 'taken', function (err, lockvalue) {
        if (err) {
            console.error(err);
        } else if (lockvalue == 1) {
            // You have the lock; process it
            //Release the key when you are done:
            rdb.del(lockkey);
        } else if (lockvalue == 0) {
            // Key is taken by someone else; try again
            setTimeout(function(){ rec(n++); }, 30<<n);            
        }
    });
})();

Answer 1

你可以使用递归函数，然后再次调用它

(function rec() {
    rdb.setnx(lockkey, 'taken', function (err, lockvalue) {
        if (err) {
            console.error(err);
        } else if (lockvalue == 1) {
            // You have the lock; process it
            //Release the key when you are done:
            rdb.del(lockkey);
        } else if (lockvalue == 0) {
            // Key is taken by someone else; try again
            rec();
        }
    });
})();

如有必要，可以使用超时来延迟递归调用