Failure Detection and Recovery in Distributed Systems: A Comprehensive Guide

Question 1

What is the main drawback of using a centralized failure detector?

Accepted Answer

Vulnerability to single points of failure

Answer

Increased complexity

Answer

Poor scalability

Answer

High latency

Question 2

Which of the following recovery techniques involves restoring the system to a previous consistent state?

Accepted Answer

Rollback recovery

Answer

Forward recovery

Answer

Compensation recovery

Answer

Transaction recovery

Question 3

What is the main difference between synchronous and asynchronous failure detectors?

Accepted Answer

Synchronous failure detectors guarantee timely detection of failures, while asynchronous failure detectors do not.

Answer

Asynchronous failure detectors guarantee timely detection of failures, while synchronous failure detectors do not.

Answer

Synchronous failure detectors are more accurate than asynchronous failure detectors.

Answer

Asynchronous failure detectors are more efficient than synchronous failure detectors.

Question 4

What is the primary purpose of using a lease-based failure detector in a distributed system?

Accepted Answer

To determine if a process is alive or has crashed by its periodic renewal of a lease

Answer

To use a quorum of processes to determine if a process has failed

Answer

To track vector timestamps of processes to monitor and detect failures

Answer

To send heartbeats to a process to determine if it is still active

Question 5

What is the significance of the suspicion level concept in the context of failure detection?

Accepted Answer

It is an indicator of the probability that a process has failed or is faulty

Answer

It determines the threshold for the number of missed heartbeats before suspecting a failure

Answer

It defines the voting threshold for quorum-based failure detection algorithms

Answer

It specifies the time interval within which a lease must be renewed to avoid suspicion

Question 6

Explain how a quorum failure detector operates in a distributed system?

Accepted Answer

It sends requests to a majority of processes and determines the outcome based on the majority response

Answer

It uses vector timestamps to compare clock values and detect failures

Answer

It monitors lease renewal and suspects processes that miss deadlines

Answer

It sends heartbeats to all processes and waits for responses

Question 7

What is the main advantage of using vector timestamp failure detectors in distributed systems?

Accepted Answer

Provision of insights into the order and causality of events in the system

Answer

Ability to detect Byzantine failures

Answer

Reduced network traffic compared to heartbeat failure detectors

Answer

Higher accuracy than quorum-based failure detectors

Question 8

Which of the following consensus algorithms is not commonly used in practical distributed system implementations?

Accepted Answer

Round Robin

Answer

Paxos

Answer

Raft

Answer

ZAB

Question 9

What is the primary goal of using distributed transactions in distributed systems?

Accepted Answer

To ensure atomicity, consistency, isolation, and durability of transactions across multiple participating nodes

Answer

To detect and recover from failures during transaction execution

Answer

To provide strict data consistency in the presence of concurrent access

Answer

To enhance the performance of database operations

Question 10

What is the primary goal of the Byzantine Generals Problem?

Accepted Answer

To achieve consensus in the presence of malicious actors

Answer

To detect and isolate faulty processes

Answer

To recover from network partitions

Answer

To prevent deadlock in distributed systems

Question 11

What is the main purpose of a recovery block in a fault tolerance system?

Accepted Answer

To execute alternative code in the event of a failure

Answer

To restart the system after a failure

Answer

To detect failures using exception handling

Answer

To prevent failures from occurring

Question 12

What is a key benefit of employing a distributed consensus algorithm?

Accepted Answer

Enhanced fault tolerance

Answer

Increased performance

Answer

Reduced latency

Answer

Lower cost

Question 13

Clarify the distinction between a fail-stop process and a fail-silent process.

Accepted Answer

A fail-stop process always terminates when it fails, while a fail-silent process might continue to operate without providing accurate results.

Answer

A fail-silent process always terminates when it fails, while a fail-stop process might continue to operate without providing accurate results.

Answer

Both fail-stop and fail-silent processes always terminate when they fail.

Answer

Both fail-stop and fail-silent processes might continue to operate without providing accurate results.

Question 14

Explain the concept of the CAP theorem.

Accepted Answer

It is impossible for a distributed system to simultaneously achieve consistency, availability, and partition tolerance.

Answer

It is possible for a distributed system to achieve all three of consistency, availability, and partition tolerance.

Answer

It is impossible for a distributed system to achieve consistency and availability.

Answer

It is impossible for a distributed system to achieve availability and partition tolerance.

Question 15

Describe the role of distributed system middleware.

Accepted Answer

To provide common services and abstractions for distributed systems

Answer

To manage the underlying network infrastructure

Answer

To implement specific application logic

Answer

To provide security and access control

Question 16

Which is NOT a common technique for failure detection in distributed systems?

Accepted Answer

Exponential backoff

Answer

Heartbeats

Answer

Suspicion mechanisms

Answer

Voting

Question 17

What is the primary goal of a failure recovery mechanism?

Accepted Answer

To automatically restore the system to a consistent state after a failure.

Answer

To prevent failures from happening in the first place.

Answer

To detect failures and notify system administrators.

Answer

To reconfigure the system to bypass faulty components.

Question 18

Which type of fault tolerance is commonly used in distributed systems?

Accepted Answer

Redundancy

Answer

Load balancing

Answer

Data encryption

Answer

Message queuing

Question 19

What is the main disadvantage of leader-based consensus protocols?

Accepted Answer

Prone to single points of failure.

Answer

Slow and inefficient.

Answer

Difficult to implement.

Answer

Require all nodes to participate in the consensus process.

Question 20

What is the fundamental purpose of a distributed hash table (DHT)?

Accepted Answer

Store and retrieve data in a distributed manner.

Answer

Ensure data consistency across all nodes.

Answer

Detect and recover from failures in the system.

Answer

Prevent data loss or corruption.

Question 21

What is the purpose of a consensus algorithm in a distributed system?

Accepted Answer

To ensure that all nodes agree on a single value

Answer

To detect and recover from failures

Answer

To improve system performance

Answer

To manage resource allocation

Question 22

What is the primary goal of a failure recovery protocol?

Accepted Answer

To restore the system to a consistent and operational state after a failure

Answer

To prevent failures from occurring

Answer

To identify the cause of failures

Answer

To roll back the system to a previous state

Question 23

What is the primary responsibility of the Paxos algorithm in fault-tolerant distributed systems?

Accepted Answer

It serves as a consensus protocol for distributed state machines

Answer

It provides a mechanism for detecting failures in the system

Answer

It helps replicate logs across multiple nodes for fault tolerance

Answer

It offers a comprehensive recovery mechanism for failed nodes

Question 24

What is the primary advantage of a leader-based failure detector compared to a leaderless one in distributed systems?

Accepted Answer

Lower latency in failure detection

Answer

Reduced network overhead

Answer

Enhanced scalability

Answer

Improved fault tolerance

Question 25

What is the primary goal of the Byzantine Generals Problem in the context of distributed systems?

Accepted Answer

To ensure that all nodes reach a consensus on a common value

Answer

To detect and isolate faulty nodes

Answer

To optimize message exchange

Answer

To prevent data loss

Question 26

What is the primary purpose of a lease in a distributed system?

Accepted Answer

To specify a maximum time that a node can hold a resource before it must renew the lease

Answer

To notify other nodes about a node failure

Answer

To protect critical resources from unauthorized access

Answer

To optimize network traffic

Question 27

Which of the following is a benefit of using a distributed file system (DFS) compared to a centralized file system?

Accepted Answer

Enhanced data availability and improved fault tolerance

Answer

Reduced storage costs

Answer

Increased data access speed

Answer

Enhanced data security

Question 28

When selecting a failure detection and recovery mechanism for a mission-critical distributed system, which factor is most crucial?

Accepted Answer

Fault Tolerance

Answer

Performance

Answer

Cost

Answer

Simplicity

Question 29

Which of the following is NOT a type of failure in distributed systems?

Accepted Answer

Syntactic error

Answer

Byzantine failure

Answer

Omission failure

Answer

Crash failure

Question 30

What is the purpose of a heartbeat mechanism in failure detection?

Accepted Answer

To periodically check the status of processes and detect failures.

Answer

To prevent processes from crashing.

Answer

To recover data from failed processes.

Question 31

Which of the following is an advantage of using a quorum-based consensus protocol for failure recovery?

Accepted Answer

It can tolerate the failure of multiple processes.

Answer

It provides strong consistency.

Answer

It is easy to implement.

Question 32

What is the difference between fail-stop and fail-silent failures?

Accepted Answer

A fail-stop process halts abruptly while a fail-silent process may continue to operate incorrectly.

Answer

Fail-stop failures can be detected by monitoring process timestamps.

Answer

Fail-stop failures are more common than fail-silent failures.

Question 33

What is the purpose of a failure detector?

Accepted Answer

To provide processes with information about the status of other processes in the system.

Answer

To prevent processes from failing.

Answer

To recover data from failed processes.

Question 34

Which of the following is a type of Byzantine failure?

Accepted Answer

A process responds to requests with arbitrary or malicious messages.

Answer

A process crashes abruptly.

Answer

A process slows down or stops responding to requests.

Question 35

What is the main goal of a fault tolerance mechanism?

Accepted Answer

To ensure that the system continues to operate correctly in the presence of failures.

Answer

To recover data from failed processes.

Answer

To prevent failures from occurring.

Question 36

Which of the following is an example of a state machine replication technique?

Accepted Answer

Paxos

Answer

Heartbeat

Answer

Leader election

Answer

Failure detection

Question 37

What is the difference between a synchronous and an asynchronous failure detector?

Accepted Answer

A synchronous failure detector provides immediate notifications of failures while an asynchronous failure detector may delay notifications.

Answer

Synchronous failure detectors are more reliable than asynchronous failure detectors.

Question 38

Which of the following is a key challenge in implementing a fault-tolerant distributed system?

Accepted Answer

Ensuring data consistency across all nodes despite failures

Accepted Answer

Detecting failures accurately and promptly to avoid false alarms or missed events

Accepted Answer

Designing recovery mechanisms to restore system consistency after failures

Answer

Preventing failures from occurring

Question 39

In a replicated state machine, which of the following techniques ensures that all replicas agree on the same state?

Accepted Answer

Consensus

Answer

Atomic multicast

Answer

Byzantine fault tolerance

Answer

Leader election

Question 40

In a Paxos-based distributed consensus algorithm, which of the following roles is responsible for making proposals?

Accepted Answer

Proposer

Answer

Leader

Answer

Learner

Answer

Acceptor

Question 41

Which of the following is a potential disadvantage of using Byzantine fault tolerance in distributed systems?

Accepted Answer

High overhead due to the need for complex mechanisms.

Answer

Improved reliability.

Answer

Simplified recovery procedures.

Answer

Reduced latency.

Question 42

Which of the following is NOT a common approach to failure detection in distributed systems?

Accepted Answer

Polling with a centralized time server

Answer

Gossip protocols

Answer

Timeouts

Answer

Heartbeat mechanism

Question 43

In a distributed system, a node experiences a failure and needs to recover. Which of the following recovery techniques involves maintaining redundant copies of data to ensure availability?

Accepted Answer

Replication

Answer

Transaction rollback

Answer

Exception handling

Answer

Checkpointing

Question 44

A distributed system employs a consensus protocol to ensure agreement among nodes. What is the primary benefit of using consensus in this context?

Accepted Answer

Fault tolerance by ensuring that all non-faulty nodes reach a common decision despite failures

Answer

Increased data storage capacity

Answer

Improved communication speed between nodes

Question 45

Consider a distributed system using a primary-backup approach for fault tolerance. What happens when the primary node fails?

Accepted Answer

The backup node assumes the primary role, taking over its responsibilities

Answer

The system halts until the primary node recovers.

Answer

The system randomly selects another node to become the primary.

Answer

The backup node informs all other nodes about the primary's failure.

Question 46

What is the fundamental distinction between a crash failure and a Byzantine failure?

Accepted Answer

Byzantine failures involve malicious or arbitrary behavior, while crash failures are unintentional and result in a node becoming unresponsive.

Answer

Crash failures are less common than Byzantine failures.

Answer

Byzantine failures are easier to detect than crash failures.

Question 47

A distributed system utilizes checkpointing for recovery. What is the primary purpose of checkpoints?

Accepted Answer

To periodically save the state of the system, allowing it to roll back to a consistent state in case of failure

Answer

To ensure that all nodes have the same version of data

Answer

To monitor the health of individual nodes in the system

Question 48

A distributed system employs Paxos for consensus. How does Paxos achieve fault tolerance?

Accepted Answer

By requiring a majority of non-faulty nodes to agree on a proposed value, ensuring that the system can tolerate failures and reach a consistent decision.

Answer

By replicating data across all nodes in the system

Answer

By using a centralized server to monitor the health of nodes

Question 49

What is the key difference between a synchronous and an asynchronous distributed system in terms of failure detection?

Accepted Answer

Synchronous systems rely on time bounds or assumptions to detect failures, while asynchronous systems do not assume reliable timeliness and handle failures based on message delivery

Answer

Asynchronous systems are more prone to failures than synchronous systems

Answer

Synchronous systems are more complex to implement than asynchronous systems

Question 50

What is the primary benefit of using a fault-tolerant system?

Accepted Answer

Increased system availability and reliability

Answer

Simplified system design

Answer

Reduced communication overhead

Answer

Improved overall performance

Question 51

Which recovery strategy involves rebuilding a failed component from scratch?

Accepted Answer

Restart

Answer

Retry

Answer

Failover

Answer

Rollback

Question 52

What is the main goal of a consensus protocol in a distributed system?

Accepted Answer

Achieving agreement among all nodes on a shared state

Answer

Optimizing communication between nodes

Answer

Detecting failures in the system

Answer

Recovering from system failures

Question 53

What is the primary function of a watchdog timer in failure detection?

Accepted Answer

Monitoring the responsiveness of nodes

Answer

Preventing deadlocks in the system

Answer

Recovering from system failures

Answer

Synchronizing system clocks

Question 54

Which of the following terms describes a system's capacity to withstand failures?

Accepted Answer

Fault tolerance

Answer

Scalability

Answer

Availability

Answer

Reliability

Question 55

Which of the following is a significant challenge in implementing failure recovery in distributed systems?

Accepted Answer

Maintaining data consistency across all nodes

Answer

Detecting failures in the system

Answer

Recovering from system failures

Answer

None of the above

Question 56

What is the key difference between failover and failback?

Accepted Answer

Failover is a temporary switch to a backup, while failback is a permanent restoration.

Answer

Failover involves switching to a backup node, while failback does not.

Answer

Failback is a temporary switch, while failover is a permanent restoration.

Answer

There is no significant difference between failover and failback.