Getting the same value from a expression rule

Question

Hi all, 
 
 I have a process model that calls an expression rule to generate a 6-character random alphanumeric string. I encountered a case where two instances of the process model were triggered at the same time (based on time logs), and both received the same generated value from the expression rule. 
 
 I understand that there's always a chance for it to generate the same value. However, I&rsquo;d like to ask: 
 Is it possible that both process models used the same instance or execution thread of the expression rule, which might explain why the same value was returned?

Shubham Aware · Answer

No, Expression rules don't share execution threads. Each process instance gets its own separate execution. Your random generator likely uses system time as a seed. When two processes run at the exact same millisecond, they get the same seed -> same random value.

Shubham Aware · Answer

Try this code once. mid(
 substitute(
 substitute(
 text(now(), "yyyyMMddHHmmssSSS"), 
 ":", ""
 ),
 " ", ""
 ),
 12,
 6
) I would recommend you to use pp!id with now() to make it more unique combination.

Harsha Sharma · Answer

Any process instance&rsquo;s id is unique always! If you want random yet unique string then consider using the process id -pp!id- along with whatever code you have for the random string!