Description

Clocks, Multicast, and COMMIT In this programming project, you will develop an n-node distributed system that provides a causally ordered multicasting service and a distributed locking scheme. The distributed system uses logical clock to timestamp messages sent/received between nodes. To start the distributed system, each node should synchronize their logical clocks to the same initial value, based on which the ordering of events can be determined among the machines. For causal ordered multicasting you can use the algorithm discussed in class. Additionally, suppose the distributed nodes have read and write access to a shared file. The last task is to implement a distributed locking scheme that prevents concurrent accesses to the shared file (this is an extra credit bonus assignment). You can use the centralized, decentralized, or the distributed algorithm to realize mutual exclusive access to the file. To simplify the design and testing, the distributed system will be emulated using multiple processes on a single machine. Each process represents a machine and has a unique port number for communication.

Implement the following

Suppose the logical clock on each machine represents the number of messages have been sent and received by this machine. It is actually a counter used by the process (or the machine emulator) to count events. Randomly initialize the logical clock of individual processes and use Berkeley’s algorithm to synchronize these clocks to the average clock. You can select any process as the time daemon to initiate the clock synchronization. After the synchronization, each process prints out its logical clock to check the result of synchronization.

Implement the causal ordered multicasting for the distributed system. Create two threads for each process, one for sending the multicast message to other nodes and one for listening to its communication port. Use vector clocks to enforce the order of messages. Once a process delivers a received message to a user, it prints out the message on screen. You can assume that the number of processes (machines) is fixed (equal to or larger than 3) and processes will not fail, join, or leave the distributed system. Implement two versions of this program, one without causally ordered multicasting and one with this feature. Compare the results of the two programs.