We've seen a problem with 2nd transaction being opened in the callback hooked to submit future of 1st transaction. That's because we invoke unlock also from a callback to submit and these callbacks can be executed in wrong order: App callback first and unlock callback after that. Which is a problem and we should be changing the execution of unlock ...

we should execute unlock right after commit is triggered, not wait until its response was returned. And to improve on that, we should return a combined future to the user of transaction, which result will be combination of commit and unlock results.