cop5615fa10quiz7key

cop5615fa10quiz7key - (b(2 What are the values of V R and...

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Quiz 7 Key COP 5615 Fall 2010 1. Suppose there are three RMs using causal order gossip, and all start with V=R=000. RM1 responds to a read/update from FSA1, which sends it update U1 with timestamp 000. After applying the update, RM1 receives another update U2 with timestamp 100. In the meanwhile, RM2 receives update U3 with timestamp 100, then RM3 receives update U4 with timestamp 200. RM1 then gossips to RM3, which then gossips to RM2. All updates that can be applied before the gossips are done, but a distributed snapshot is taken after the gossips are received but before the enabled updates are applied at each RM. In all cases below, indicate which updates in the log have been applied with “A”. the ones that are enabled but not yet applied with “E”, and the ones that are delayed and not yet enabled with “D”. (a) (1) What are the values of V, R, and the update log at RM1?
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Unformatted text preview: (b) (2) What are the values of V, R, and the update log at RM2? (c) (2) What are the values of V, R, and the update log at RM3? Answer : Events at RM1: V = R = 000 Receive u1=000, r1=100; R = 100 A; V = R = 100 Receive u2=100, r2=200; R = 200 A; V = R = 200 Send gossip with log (u1 and u2, as above, both A) Events at RM2: V = R = 000 Receive u3=100, r3=110; R = 110 – D; V = 000, R = 110 Receive gossip from RM3 with u1, u2, u4; V = 000, R = 211 Log: u1=000, r1=100 E u2=100, r2=200 E (after u1) u3=100, r3=110 E (after u1) u4=200, r3=201 E (after u2) Events at RM3: V = R = 000 Receive u4=200, r4=201- D; V = 000, R = 201 Receive gossip from RM1 with u1, u2; V = 000, R = 211 Log: u1=000, r1=100 E u2=100, r2=200 E (after u1) u3=100, r3=110 E (after u1) u4=200, r3=201 E (after u2)...
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