What's the best practice to ensure atomic read of a database table using JDBC?

Question

I have an java application reading from a database table for jobs to process, and I may have multiple instances of this application running on different servers as each job is i

Answer 1

When using databases of a transactional nature, one popular practice is to perform ROW-LEVEL LOCKING. Row-level locks prevent multiple transactions from modifying the same row. SELECT for UPDATE is an easy way to achieve this effect. Assuming you have a processes table:

SELECT process_id, status 
from processes
for UPDATE of status SKIP LOCKED;

When done processing, issue

update processes set status = 'updated'
where process_id = :process_id;             --from before

Issue

commit;

to release the lock.

Here's an actual example

Disclaimer: SELECT FOR UPDATE is a form of pessimistic locking and has its caveats as explained by Burleson. However, it might be a viable solution if the client is not web-based and extremely concurrent.