|
Recently, personal workstation and local area network come to
life of people. This paper attempts to combine this type of
computing power to let people to construct a
distributed application by use of an object based system. This
system which is called distributed object manager can let
people create an object, destroy an object, migrate an
object, etc. The RPC ( Remote Procedure Call) is used as a
message passing mechanism between any two objects and we
establish the system using the client-server model. In this
paper, we first introduce the life cycle of an object to
discuss the state transition of an object, then we discuss the
activities of object management in detail, including long,
short and medium life cycle model, object naming, object
creation, object destruction, object invocation, object
migration and object locating. There are many problems in this
type of system we must solve. Because it is important to keep
track of objects in this system, we use an object name server
to serve as this purpose. The object name server keeps all
the informations of an object. Checkpointing lets the
object survive the disaster when the machine crashes. When
an object is migrated, there may be an invocation failure.
Besides the object name server is used to keep track of the
location of an object, forwarding address and the object
locating algorithm are used to locate the invoked object
because it may have been migrated. At last, we show our
experiences of constructing this object manager. We will
discuss and compare the pros and cons of its methods.
|