Sage-Tips

What is a vector clock used for?

A vector clock is a data structure used for determining the partial ordering of events in a distributed system and detecting causality violations. Just as in Lamport timestamps, inter-process messages contain the state of the sending process’s logical clock.

What is the advantage of vector clock over Lamport’s logical clock?

Vector Clocks represent an extension of Lamport Timestamps in that they guarantee the strong clock consistency condition which (additionally to the clock consistency condition) dictates that if one event’s clock comes before another’s, then that event comes before the other, i.e., it is a two-way condition.

What is the purpose Vector Clocks in Dynamo?

Dynamo uses vector clocks [12] in order to capture causality between different versions of the same object. A vector clock is effectively a list of (node, counter) pairs. One vector clock is associated with every version of every object.

What is vector clock algorithm?

Vector Clock is an algorithm that generates partial ordering of events and detects causality violations in a distributed system. This algorithm helps us label every process with a vector(a list of integers) with an integer for each local clock of every process within the system.

What are the limitations of Lamport’s logical clock?

The problem with Lamport Timestamps is that they can’t tell if events are concurrent or not. This problem is solved by Vector Clocks.

Does DynamoDB use vector clocks?

DynamoDB uses vector clocks in order to capture causality between multiple versions of an object. A vector clock is a list of (node, counter) pairs. One vector clock is associated with one version of every object.

How does Amazon Dynamo work?

DynamoDB uses hashing and B-trees to manage data. Upon entry, data is first distributed into different partitions by hashing on the partition key. Each partition can store up to 10GB of data and handle by default 1,000 write capacity units (WCU) and 3,000 read capacity units (RCU).

What is difference between physical clock and logical clock?

Question 856 : The difference between logical and physical clocks? Physical clocks measure the time of day and Logical clocks are used to mark relationships among events in a distributed system. Both measures the time of day.

Why does Cassandra not need a vector clock?

Siblings — multiple versions generated by conflicting updates — are difficult to deal with in practice, to the point that Riak makes last-write-wins the default despite the high potential for data loss. This is why Cassandra and later Riak both had to go beyond vector clocks when implementing counters.

What is the purpose of Lamport’s logical clocks explain?

Lamport’s Logical Clock was created by Leslie Lamport. It is a procedure to determine the order of events occurring. It provides a basis for the more advanced Vector Clock Algorithm.