・A concept of the actor model, for a distributed system
In Previous article, I described that an information is created by connecting data semantically, and at UI tier in system, user’s operations connect data and transfer to persistent tier in system, so It’s state should be managed in system. In a distributed system, state is not shared at persistent tier but shared at middleware with other systems, services or users. And persistent tier is ready for individual system respectively in distributed system.
State full middleware is feature of distributed system, it’s design and implementation is so hard. As a result, A concept of the actor model was born for one of respond as solution for cost reduction of distributed system development. In the actor model, an actor send message of function execution to another actor, and also an actor can create another actor necessary. An actor send message asynchronously and does not wait response of sent message, so the model is fit to concurrent execution. Then the message is store at queue of actor which receive it.
For achieve this, an actor have to know an address of an actor to send message. And need to cache the state. An address of an actor to send message is resolved by distributed directory. A cache of state is covered by persistent tier of each actors respectively.