failure detection
DESCRIPTION
Failure Detection. The ping- a ck failure detector in a synchronous system satisfies A: completeness B: a ccuracy C: n either D: both. Failure Detection. The ping- a ck failure detector in an asynchronous system satisfies A: c ompleteness B: a ccuracy C: n either D: both. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/1.jpg)
Failure Detection
• The ping-ack failure detector in a synchronous system satisfies– A: completeness– B: accuracy– C: neither– D: both
![Page 2: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/2.jpg)
Failure Detection
• The ping-ack failure detector in an asynchronous system satisfies– A: completeness– B: accuracy– C: neither– D: both
![Page 3: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/3.jpg)
Vector timestamps
• Which of these timestamps is concurrent with (1,2,3)– A: (1,3,3)– B: (1,2,1)– C: (4,5,6)– D: (2,3,2)
![Page 4: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/4.jpg)
Consistent Cut
• Which of these cuts is consistent?– A: cut1– B: cut2
P1
P2
e1
e2
e3
e4
cut1 cut2
![Page 5: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/5.jpg)
Reliable Multicast
• In reliable multicast, what is the definition of “Integrity”?– A: A correct process p delivers a message m at
most once.– B: If a correct process delivers message m, then all
the other correct processes in group(m) will eventually deliver m.
– C: If a correct process multicasts (sends) message m, then it will eventually deliver m itself.
![Page 6: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/6.jpg)
Multicast
• State true or false: Any multicast that is both FIFO-ordered and totally ordered is thereby causally ordered.– A: True– B: False
![Page 7: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/7.jpg)
Consensus
• For which of the following situations, consensus is possible: – A: synchronous system, failures possible– B: asynchronous system, failures impossible– C: both– D: neither
![Page 8: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/8.jpg)
Mutual Exclusion
• What properties does Token Ring mutual exclusion algorithm satisfy– A: Safety only– B: Safety & liveness– C: Safety & ordering– D: Safety, liveness, and ordering– E: none of the above
![Page 9: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/9.jpg)
Mutual Exclusion
• What properties does Ricart & Agrawala mutual exclusion algorithm satisfy– A: Safety only– B: Safety & liveness– C: Safety & ordering– D: Safety, liveness, and ordering– E: none of the above
![Page 10: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/10.jpg)
Leader Election
• Leader election in asynchronous systems is– A: possible– B: impossible
![Page 11: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/11.jpg)
Leader Election
• Bully algorithm guarantees:– A: Safety– B: Liveness– C: Both– D: Neither
![Page 12: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/12.jpg)
Byzantine Generals Algorithm
• What is the minimum number of nodes required to achieve agreement in Byzantine generals algorithm with f Byzantine faulty nodes?– A: f+1– B: 2f+1– C: 3f+1
![Page 13: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/13.jpg)
Routing Algorithms
• In which routing algorithm each node talks only to its directly connected neighbors, but it tells them everything it has learned?– A: Link State routing algorithm– B: Distance Vector routing algorithm
![Page 14: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/14.jpg)
Chord
• How much state does a Chord peer maintain?– A: O(1)– B: O(log N / log log N)– C: O(log N)– D: O(√N)– E: O(N)
![Page 15: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/15.jpg)
Idempotence
• Idempotent algorithms are needed when using– A: at most once invocation semantics– B: at least once invocation semantics
![Page 16: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/16.jpg)
RMI
• To facilitate RMI, a stub object is maintained– A: on the client– B: on the server
![Page 17: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/17.jpg)
2PL
• Two-phase locking ensures that:– A: Transactions maintain serial equivalence– B: Deadlocks do not occur– C: Distributed transactions can commit atomically
![Page 18: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/18.jpg)
Quorum
• In a system of 6 nodes, which of these is an invalid quorum configuration?– A: w=4, r=3– B: w=6, r=3– C: w=5, r=1– D: w=6, r=1– E: w=4, r=5
![Page 19: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/19.jpg)
Available Copies Replication
• Available copies replication captures which two properties from the CAP theorem?– A: Consistency and Availability– B: Consistency and Partition-tolerance– C: Availability and Partition-tolerance
![Page 20: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/20.jpg)
Gossip protocols
• What is the worst-case latency for distributing a message among N nodes through a gossip protocol– A: O(log N)– B: O(N0.5)– C: O(N)– D: unbounded
![Page 21: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/21.jpg)
Gossip protocols
• What is the expected latency for distributing a message among N nodes through a gossip protocol– A: O(log N)– B: O(N0.5)– C: O(N)– D: unbounded
![Page 22: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/22.jpg)
Two-phase commit
• If a participant has responded yes to a canCommit call and has not heard from the coordinator for a long time, it should:– A: abort– B: commit– C: call getDecision on the coordinator– D: keep waiting
![Page 23: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/23.jpg)
Routing Algorithms
• Count-to-infinity is a problem of– A: Link State routing algorithm– B: Distance Vector routing algorithm
![Page 24: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/24.jpg)
Distributed Shared Memory
• False sharing leads to:– A: Excessive page transfers– B: Violations of sequential consistency– C: Deadlock
![Page 25: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/25.jpg)
CODA
• Which of the CAP “vertices” does CODA sacrifice?– A: Consistency– B: Availability– C: Partition-tolerance
![Page 26: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/26.jpg)
Paxos
• In Paxos, a distinguished proposer is used to:– A: ensure safety– B: ensure liveness– C: optimize performance
![Page 27: Failure Detection](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568165f7550346895dd91e38/html5/thumbnails/27.jpg)
Paxos
• In Paxos, a distinguished listener is used to:– A: ensure safety– B: ensure liveness– C: optimize performance