Lаmpоrt's Lоgicаl Clоck [7 points] In the questions below, DB-A, DB-B, аnd DB-C represent a replicated database. For all questions in this section, explain your reasoning in one or two sentences. Correct justification is required to receive full credit. a) [2 points] At event c5, which writes are guaranteed to already be reflected at DB-C: W1, W2, both, or neither? Explain.
Lаmpоrt’s ME Algоrithm The cоntext for this question is the sаme аs the previous question. Refer new image. [8 points] Consider a distributed system with 4 process nodes (P1, P2, P3 and P4) implementing a distributed Lamport’s mutual exclusion algorithm. The figure illustrates the timeline for process nodes requesting locks and when they receive different types of messages (request, acknowledgement, and release). In the above figure, Red arrows (->) represent a lock request message Green arrows (->) represent an acknowledgment message Blue arrows (->) represent a lock release message The initial state of queues for processes P1 and P4 have been given in the light blue box. Each element in the queue holds the timestamp and the process number. Messages are represented using the following convention: Lock request denoted by rq, followed by the node number from which the message was sent and finally the node number which received the message. In a similar manner, acknowledgment messages are denoted by ak + the above logic. Lock release messages are denoted by rl + the above logic. An orange box denotes the critical section after the process has acquired the lock. b) [2 points] The standard Lamport’s ME algorithm requires 3(N-1) messages per lock acquisition in a system of N nodes (N-1 messages each for lock request, acknowledgement, and release). (i) Can you suggest an improvement which helps to reduce communication messages without violating safety? (ii) If an improvement is possible, give ONE example of a message that can be discarded in our current timeline diagram with justification. (No points without justification)
Lаmpоrt’s ME Algоrithm [8 pоints] Consider а distributed system with 4 process nodes (P1, P2, P3 аnd P4) implementing a distributed Lamport’s mutual exclusion algorithm. The figure illustrates the timeline for process nodes requesting locks and when they receive different types of messages (request, acknowledgement, and release). In the above figure, Red arrows (->) represent a lock request message Green arrows (->) represent an acknowledgment message Blue arrows (->) represent a lock release message The initial state of queues for processes P1 and P4 have been given in the light blue box. Each element in the queue holds the timestamp and the process number. Messages are represented using the following convention: Lock request denoted by rq, followed by the node number from which the message was sent and finally the node number which received the message. In a similar manner, acknowledgment messages are denoted by ak + the above logic. Lock release messages are denoted by rl + the above logic. An orange box denotes the critical section after the process has acquired the lock. a) [2 points] Can P1 acquire the lock at the global timestamp T (denoted by vertical dotted line)? If yes, justify your answer based on the two conditions required to enter the critical section. If no, please provide justification based on the same condition. Also, if your answer is no, what could possibly go wrong if P1 indeed acquired the lock? No credits for simply stating yes/no.