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I'm using the below function to generate UUID
UUID.randomUUID().toString()
In production we have 50+ servers (application server - each is a JVM on its own) and for requests that land in these servers, as a first step we generate a UUID which essentially uniquely identifies a transaction.
What we are observing is that in Server 6 and Server 11, the UUIDs generated are matching at least for 10 to 15 messages per day which is strange because given the load i.e. about 1 million transactions a day, these UUIDs being duplicate within the same day is very odd.
This is what we have done so far
So far we haven't been able to trace the issue, my question is basically if there is something at JVM level we are missing or UUID parameter that we need to set for this one off kind of an issue?
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From the documentation and wikipedia we see that randomUUID is good - but there is a very small chance that duplicates can be generated.
Alternatively, you can rely upon a randomly generated ID. In our experience, a random number of 7 digits is sufficiently random, to avoid duplicate IDs. Do this most simply with SurveyCTO's uuid() function in a calculate field to create and ID that is a random combination of numbers and letters.
This version of UUID is generated randomly. Although the random UUID uses random bytes, four bits are used to indicate version 4, while two to three bits are used to indicate the variant. These can be created using a random or pseudo-random number generator.
a uuid is “in theory” a 128-bit random number. that's a HUGE number (like atoms in the universe big) and if the algorithms were truly random (which they're not) it would be effectively impossible to have a duplicate.
Given time, I'm sure you'll find the culprit. In the meantime, there was a comment that I think deserves to be promoted to answer:
You are generating pseudo random UUIDs at multiple locations. If you don't find other bugs, consider either generating all the pseudo random UUIDs at one location, or generate real random UUIDs
So create a UUID server. It is just a process that churns out blocks of UUIDs. Each block consists maybe 10,000 (or whatever is appropriate) UUIDs. The process writes each block to disk after the process verifies the block contains no duplicates.
Create another process to distribute the blocks of UUIDs. Maybe it is just an a web service that returns an unused block when it gets a request. The transaction server makes a request for a block and then consumes those UUIDs as it creates transactions. When the server has used most of its assigned UUIDs, it requests another block.
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