In this assignment you will extend the Assignment 1 model above to support active replication . For that purpose, this assignment requires you to add:
a) Three Replica Manager (RM) for the server component that tracks locations of trams and
b) A server Front End (FE) with which Tram clients will communicate using RMI. The FE will forward remote method calls to all available RMs and forward results back to Tram clients using RMI.
The new system architecture is shown in the following diagram:
Front End (FE) hides replication management from the client, communicates with one or more Replica Managers, provides replication transparency. Each RM is a replication of the Tram Tracking server, process incoming requests independently but identically.
System requirements:
- ● The Trams will only communicate with the server Front End via RMI using the Remote interface shown in the diagram above.
- ● The system consists of three Replica Managers. Each RM is a replication of the Tram Tracking server to provide communication with server FE via RMI using the same Remote interface shown in the diagram above.
o In this assignment, FE and RMs are all running on localhost, but at different ports (in reality, they can run on different servers having different IP addresses and ports)
- ● The FE must always be running and at least one RM will be running at any given time to provide fault tolerance.
- ● When a Tram makes a remote method call to the server Front End:
- FE will first call a listTramService() method to find out which RM is running. The
results of this listTramService() call should also be printed out on the Console of the
FE, for example: RM1 on | RM2 off | RM3 on.
- For each RM that is running, the FE will call the corresponding remote method on that
RM, passing the input Message object and receiving a return Message object from that RM. Then the FE will forward that returned Message object to the Tram client. All of this will be performed using RMI as shown in the above diagram.
- FE will first call a listTramService() method to find out which RM is running. The
- ● While the system is running, at most 2 RMs can be killed and the system should continue simulating the tram movement as usual.
What to demonstrate
Demos will be running in Week 11 and 12 in the labs. No concurrency control needs to be implemented, so users can interfere with each other’s operations in a way that leads to error conditions, as allowed by the Unix file system.
You need to demonstrate the system with one server FE, three RMs and several Trams running at the same time. You will need to show service continuity in presence of failure: two RMs will be killed and the system should continue simulating the tram movement.
The End