锁的基本逻辑——互斥

basic logic of lock - mutual exclusion

我正在为互斥锁的逻辑而苦恼;我在这里检查密钥是否被拿走,如果没有,我们拿走它,完成后释放它;但是你能帮我看看我怎样才能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);            
        }
    });
})();

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();
        }
    });
})();

如果需要,可以使用超时来延迟递归调用