A logical clock is a mechanism for capturing chronological and causal relationships in a distributed system. Often, distributed systems may have no physically synchronous global clock. In many applications (such as distributed GNU make), if two processes never interact, the lack of synchronization is unobservable and in these applications it is enough for the processes to agree on the event ordering (i.e., logical clock) rather than the wall-clock time.[1] The first logical clock implementation, the Lamport timestamps, was proposed by Leslie Lamport in 1978 (Turing Award in 2013).
In logical clock systems each process has two data structures: logical local time and logical global time. Logical local time is used by the process to mark its own events, and logical global time is the local information about global time. A special protocol is used to update logical local time after each local event, and logical global time when processes exchange data.[2]
Applicationsedit
Logical clocks are useful in computation analysis, distributed algorithm design, individual event tracking, and exploring computational progress.
Algorithmsedit
Some noteworthy logical clock algorithms are:
Lamport timestamps, which are monotonically increasing software counters.
Vector clocks, that allow for partial ordering of events in a distributed system.
Matrix clocks, an extension of vector clocks that also contains information about other processes' views of the system.
Referencesedit
^"Distributed Systems 3rd edition (2017)". DISTRIBUTED-SYSTEMS.NET. Retrieved 2021-03-20.
^Chapter 3: Logical Time // Ajay Kshemkalyani and Mukesh Singhal, Distributed Computing: Principles, Algorithms, and Systems, Cambridge University Press, 2008
External linksedit
// Roberto Baldoni, Silvia Bonomi. MIDLAB, Sapienza University of Rome
Chapter 3: Logical Time // Ajay Kshemkalyani and Mukesh Singhal, Distributed Computing: Principles, Algorithms, and Systems, Cambridge University Press, 2008
Distributed Systems 06. Logical Clocks // Paul Krzyzanowski, Rutgers University, Fall 2014
January 01, 1970
logical, clock, logical, clock, mechanism, capturing, chronological, causal, relationships, distributed, system, often, distributed, systems, have, physically, synchronous, global, clock, many, applications, such, distributed, make, processes, never, interact,. A logical clock is a mechanism for capturing chronological and causal relationships in a distributed system Often distributed systems may have no physically synchronous global clock In many applications such as distributed GNU make if two processes never interact the lack of synchronization is unobservable and in these applications it is enough for the processes to agree on the event ordering i e logical clock rather than the wall clock time 1 The first logical clock implementation the Lamport timestamps was proposed by Leslie Lamport in 1978 Turing Award in 2013 Contents 1 Local vs global time 2 Applications 3 Algorithms 4 References 5 External linksLocal vs global time editIn logical clock systems each process has two data structures logical local time and logical global time Logical local time is used by the process to mark its own events and logical global time is the local information about global time A special protocol is used to update logical local time after each local event and logical global time when processes exchange data 2 Applications editLogical clocks are useful in computation analysis distributed algorithm design individual event tracking and exploring computational progress Algorithms editSome noteworthy logical clock algorithms are Lamport timestamps which are monotonically increasing software counters Vector clocks that allow for partial ordering of events in a distributed system Version vectors order replicas according to updates in an optimistic replicated system Matrix clocks an extension of vector clocks that also contains information about other processes views of the system References edit Distributed Systems 3rd edition 2017 DISTRIBUTED SYSTEMS NET Retrieved 2021 03 20 Chapter 3 Logical Time Ajay Kshemkalyani and Mukesh Singhal Distributed Computing Principles Algorithms and Systems Cambridge University Press 2008External links editDistributed System Logical Time Roberto Baldoni Silvia Bonomi MIDLAB Sapienza University of Rome Chapter 3 Logical Time Ajay Kshemkalyani and Mukesh Singhal Distributed Computing Principles Algorithms and Systems Cambridge University Press 2008 Distributed Systems 06 Logical Clocks Paul Krzyzanowski Rutgers University Fall 2014 Retrieved from https en wikipedia org w index php title Logical clock amp oldid 1072010149, wikipedia, wiki, book, books, library,
