- 1.1 Introduction To Distributed Systems
- 1.2 Examples Of Distributed Systems
- 1.3 Main Characteristics
- 1.4 Advantages And Disadvantages Of Distributed System
- 1.5 Design Goals
- 1.6 Main Problems
- 1.7 Models Of Distributed System
- 1.8 Resource Sharing And The Web Challenges
- 1.9 Types Of Distributed System: Grid, Cluster, Cloud
- Chapter 1 - Slides
- Case Study: Www As Distributed System
- 2.1 Introduction
- 2.2 Communication Between Distributed Objects
- 2.3 Remote Procedure Call
- 2.4 Events And Notifications
- 2.5 Java Rmi Case Study
- 2.6 Introduction To Dfs
- 2.7 File Service Architecture
- 2.8 Sun Network File System
- 2.9 Introduction To Name Services
- 2.10 Name Services And Dns
- 2.11 Directory And Discovery Services
- 2.12 Comparison Of Different Distributed File Systems
- Chapter 2- Slides
- 8.1 Transactions
- 8.2 Nested Transaction
- 8.3 Locks
- 8.4 Optimistic Concurrency Control
- 8.5 Timestamp Ordering
- 8.6 Comparison Of Methods For Concurrency Control
- 8.7 Introduction To Distributed Transactions
- 8.8 Flat And Nested Distributed Transactions
- 8.9 Atomic Commit Protocols
- 8.10 Concurrency Control In Distributed Transactions
- 8.11 Distributed Deadlocks
- 8.12 Transaction Recovery
- 2079 Bhadra-Regular
- 2076 Chaitra, Ashwin- Ioe Old Question Solution, Distributed System
- 2078 Bhadra- Ioe Old Question Solution, Distributed System
- 2069-Chaitra- Ioe Old Question Solution, Distributed System
- 2075- Regular And Back- Ioe Old Question Solution, Distributed System
- 2070-Back- Ioe Old Question Solution, Distributed System
- 2074 Regular/ Back- Ioe Old Question Solution, Distributed System
- 2072 Chaitra / Kartik- Ioe Old Question Solution, Distributed System
- 2079 Bhadra/ 2080 Baishakh- Ioe Old Question Solution, Distributed System
- 2071- Shrawan- Ioe Old Question Solution, Distributed System
- 2071 Chaitra- Ioe Old Question Solution, Distributed System
- 2070 Chaitra- Ioe Old Question Solution, Distributed System
- 2070 Ashadh-Ioe Old Question Solution, Distributed System
DISTRUBUTED SYSTEM NOTES,IOE, TU,BCA
LOGICAL CLOCK IN DISTRIBUTED SYSTEM
A logical clock in a distributed system is a mechanism used to order events and capture causality without relying on physical time. It helps in synchronizing events across different nodes to ensure a consistent and coherent sequence of operations. There are two main types of logical clocks: Lamport timestamps and vector clocks.
Lamports Logical Clock
Lamport's Logical Clock is a mechanism used in distributed systems to order events in a way that respects causality, even when there is no global physical clock. This concept was introduced by Leslie Lamport in 1978 and plays a critical role in ensuring the consistency and coordination of distributed systems.
To synchronize logical clocks, Lamport defined a relation called happens-before.The expression a ->b is read as ‘a happens before b’ and means that all processes agree that event a occurs then event b occurs.From the definition of the happened-before relation, the clock condition mentioned above is satisfied if the following conditions hold:
- i. If a and b are two events within the same process and a occurs before b then a->b is true
- Ii. If a is message sent by process and b is the receipt of that message by process then a->b is also true.
- A message cannot be received before it is sent , or even at the same time it is sent, since it takes finite, nonzero amount of time to arrive.
The algorithm follows some simple rules:
- A process increments its counter before each event in that process.
- When a process(a) sends a message to a process(b), it includes its counter value with the message.
- On receiving a message, the counter of the recipient(b) is updated, if clock of receiver is less than clock of sender process: the receiver sets its local clock to c(b)=c(a)+1, where c(a) and c(b) are clock of process a and b repectively.
- The counter is then incremented by 1 before the message is considered received.
- Also each process adjust its clock to their respective interval.
