Question

I’m using Redis in my application and one thing is not clear for me. I save an object with a random generated string as its key. However I would like to check if that key exists. I am planning to use while loop however I am not sure how would I struct it according to Redis. Since if I would like to check for once, I would do;

redisClient.get("xPQ", function(err,result){
   if(result==null)
      exists = false
});

But I would like use the while loop as;

while(exists == false)

However I cannot build the code structure in my head. Would the while be inside the function or outside the function?

Answer 1

In general, you shouldn’t check for existence of a key on the client side. It leads to race conditions. For example, another thread could insert the key after the first thread checked for its presence.

You should use the commands ending with NX. For example – SETNX and HSETNX. These will insert the key only if doesn’t already exist. It is guaranteed to be atomic.