some notion in terracotta

Shared Roots

A shared root is a class data member that is transparently mirrored across all like-configured DSO applications running against the same DSO server. The term root refers to the fact that the field may represent the top of an arbitrarily large object graph. For instance, a java.util.ArrayList is a collection of java.lang.Objects, each of which may also be composed of further sub-objects. A root can also be a simple primitive such as an int or boolean.

Distributed Locks

A distributed lock is a form of a distributed semaphore, protecting areas of code that modify members of a shared root graph from simultaneous access and providing the hook DSO uses to synchronize data values across to the server for subsequent broadcast to other connected clients. In the distributed programming paradigm, a lock is analogous to a distributed synchronized method.

There are two categories of locks, named and automatic.

Named Locks

A named locks is meant to be used with code not specifically written for multi-thread safety. A method can be associated with a particular name, meaning that all similarly named methods use the same lock. In other words, if two methods share the same lock name and one method invokes the other, only a single actual lock will be taken out for the duration of the outer invocation.

Automatic Locks

An auto lock is meant for the case were the code is written with multiple threads in mind, using the synchronized keyword to demarcate protected areas. A synchronized block or method denotes a section of control flow that will be serialized with respect to thread access. Only a single thread can enter the block at a time.