Vector Clock in Distributed System clock design vector.

Vector Clock in Distributed System clock design vector.

https://www.gyanodhan.com/video/7A2.%20Computer%20Science/Distributed%20Computing/329.%20Vector%20Clock%20in%20Distributed%20Systemclock%20design%20vector.mp4

Vector Clock in Distributed Systems – Clock Design & Concept

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What is a Vector Clock?

A Vector Clock is a logical clock mechanism used in distributed systems to capture causal relationships between events — especially to determine whether one event happened before another (→ “happened-before” relation).

Unlike Lamport clocks (which can only show if events are ordered or concurrent), vector clocks can precisely track causality.

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Why is it Needed?

In distributed systems, due to the absence of a global clock:

• It’s hard to know the actual order of events.
• Vector clocks help track causal dependencies among processes.

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Vector Clock Design (Structure)

Each process in a distributed system maintains a vector of integers — one entry for every process in the system.

Example:

For a system with 3 processes P1, P2, P3, each process maintains a vector clock like:

VC(P1) = [v1, v2, v3]

Where:

• v1: P1’s own clock
• v2: P1’s knowledge of P2’s clock
• v3: P1’s knowledge of P3’s clock

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How Vector Clocks Work (Rules):

1. Initialization:
   • Every process starts with vector [0, 0, ..., 0]
2. Local Event:
   • A process increments its own clock.
   • VC[i] = VC[i] + 1
3. Send Message:
   • Increment local clock.
   • Send the entire vector along with the message.
4. Receive Message:
   • Increment own clock.
   • Take the element-wise maximum of the received vector and own vector.

   VC[i] = max(VC[i], received VC[i]) for all i
   

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Example:

Let’s assume:

• P1 sends a message to P2
• VC(P1) before sending: [2,0,0]
• P1 sends message → [3,0,0] to P2

P2 receives message when its clock was [1,2,0]
Now it computes:

VC(P2) = max([1,2,0], [3,0,0]) → [3,2,0]
Then increments its own component → [3,3,0]

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Interpretation of Vector Clocks:

For two events with vector clocks VC1 and VC2:

• VC1 < VC2 → VC1 happened before VC2
• VC1 || VC2 → Events are concurrent (no causal relationship)

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Benefits of Vector Clocks:

• Captures causality precisely.
• Helps in version control, conflict resolution, and event ordering.
• Used in distributed databases, Git, blockchains, etc.

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Limitations:

• Requires O(n) space and communication overhead (where n = number of processes).
• Not scalable for large systems.

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Would you like a diagram, visual animation, or real-world application (like in DynamoDB or Git)? I can also provide this in Hindi if you prefer.

Vector Clock in Distributed System clock design vector.

LOGICAL AND VECTOR CLOCKS USED IN …

A Practical Tour of Vector Clock Systems.

Clocks in Distributed System

Chapter 3: Logical Time