Virtual Labs

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Aim

Theory

Pretest

Procedure

Simulation

Posttest

References

Contributors

Feedback

2 phase commit With different failures

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When you dropped a single VOTE_COMMIT message by breaking a link, what decision did the coordinator make and why?

a: GLOBAL_COMMIT, because all participants were READY Explanation

Explanation

b: GLOBAL_ABORT, because a vote was missing after timeout Explanation

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c: GLOBAL_COMMIT, because missing votes default to commit Explanation

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d: It blocked indefinitely, waiting for the missing vote Explanation

Explanation

Why is durable logging of the ‘READY’ state essential for a participant that crashes before the global decision?

a: So it can vote again in a new transaction Explanation

Explanation

b: So it knows to re-send PREPARE on recovery Explanation

Explanation

c: So it can query the coordinator for the correct decision upon recovery Explanation

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d: So it commits immediately on restart Explanation

Explanation

In the ‘Coordinator Crash’ scenario, what mechanism guarantees all participants eventually see the same decision?

a: Participants gossip amongst themselves Explanation

Explanation

b: Coordinator re-broadcasts its decision on recovery Explanation

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c: Participants abort if they miss any message Explanation

Explanation

d: Coordinator logs nothing until every ACK arrives Explanation

Explanation

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