Remote Method Invocation

1
Remote Method Invocation
2
B
A
C
Java Virtual Machine
A sends a message to B, also known as method
invocation
3
JVM
JVM
JVM
JVM
You have no idea where your objects are.
4
Object parameter
Invoke method( )
Return( )
The parameters might not be known in the remote
jvm. The returned object may not also be known
by the local jvm.
5
Return Class Def
Client Object
Ask for Class Definition
Return Class Def
Ask for Class Definition
Return Stub
Invoke method
Ask for service
RMIRegistry
Server Object
6
Immortality
Server Object is dead!
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RMI Activation Subsystem

• Re-instantiate server when system resets or
  crashes
• Maintain state of server to be able to survive
• software failure and system reboot.

8
RMI's concept of Fault Tolerance
Activatable Object
A
B
Jvm
Contact daemon
Resurrect server
Returns new stub
Jvm
Server is dead
Object A did not know remote object died. It
still got the service it wanted.
OS
9
RMI Compute Server
Computable c
DoJob ( ) throws RemoteException
GetResult()
Return
Compute()
Result
Compute server
10
Compute Farm
Master
Computing the number of prime between 0 and
1000000