Question

I am generating a unique and random alphanumeric string segment to represent certain links that will be generated by the users. For doing that I was approaching with “uuid” number to ensure it’s uniqueness and randomness, but, as per my requirements the string shouldn’t be more than 5 characters long. So I dropped that idea.

Then I decided to generate such a string using random function of ruby and current time stamp.
The code for my random string goes like this:-

 temp=DateTime.now
 temp=temp + rand(DateTime.now.to_i)
 temp= hash.abs.to_s(36)   

What I did is that I stored the current DateTime in a temp variable and then I generated a random number passing the current datetime as parameter. Then in the second line actually added current datetime and random number together to make a unique and random string.

Soon I found,while I was testing my application in two different machines and send the request at the same time, it generated the same string(Though it’s rare) once after more than 100 trials.

Now I’m thinking that I should add one more parameter like mac address or client ip address before passing to_s(36) on temp variable. But can’t figure out how to do it and even then whether it will be unique or nor…

Thanks….

Answer 1

SecureRandom in ruby uses process id (if available) and current time. You can use the urlsafe_base64(n= 16) class method to generate the sequence you need. According to your requirements I think this is your best bet.

Edit: After a bit of testing, I still think that this approach will generate non-unique keys. The way I solved this problem for barcode generation was:

barcode= barcode_sql_id_hash("#{sql_id}#{keyword}")

Here, your keyword can be time + pid.