Is there a way in Tarantool to check state of tuple before performing update (optimistic lock check / CAS pattern)?

I try to find information about way to implement optimistic locks in Tarantool DB. This case doesn't covered in documentation so I can't get possible way for such action.

My goal is to find a way to resolve potential data collisions for concurent update of same tuples from multipal clients ( application servers ). For such load there is always lag between reading tuple and updating it - so there is room for race conditions. I try to avoid pessimistic locks in distributed system - for such locking we need additional component - and any addition of new component mast be done with many considerations in mind.

Solution

That would be a stored procedure similar to the following (code is simplified):

function update_cas(key, tuple, version)
   local old = space:get(key)
   if old.version ~= version then error('Oops!') end
   tuple[VERSION_FIELD_NUMBER] = version + 1
   space:replace(tuple)
end

I hope it gives you the idea.