what exactly is state machine . Please explain
Course: Distributed Systems for Practitioners - Learn Interactively
Lesson: Communication among Raft Nodes
Hi @Ravish_Aanand_4-Yr_B !!
In the context of the Raft consensus algorithm, “safely applied to the state machine” refers to the process by which entries in the replicated log are executed in a coordinated and consistent manner across all nodes in the cluster. Let’s break down the concepts:
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State Machine:
- In computer science, a state machine is an abstract machine that can be in one of a finite number of states at any given time. It transitions from one state to another in response to events or inputs.
- In the context of distributed systems like Raft, the state machine represents the desired functionality or behavior that the system should exhibit. It could be anything from maintaining a database, executing commands, processing transactions, etc.
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Safely Applied:
- Raft ensures that entries in its replicated log are safely applied to the state machine to maintain consistency and reliability across all nodes.
- “Safely applied” means that the entries are executed on the state machine in a way that guarantees consistency and correctness, even in the presence of failures or network partitions.
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Consistency and Safety:
- Raft achieves safety by requiring that a log entry is committed before it is applied to the state machine. Committing an entry means that it has been replicated and acknowledged by a majority of nodes in the cluster.
- Once an entry is committed, Raft ensures that it is applied exactly once and in the same order across all nodes’ state machines. This ensures consistency and prevents divergence among nodes.
In summary, “safely applied to the state machine” in the context of Raft means that log entries are executed on the state machine in a consistent and reliable manner, following the rules and guarantees provided by the Raft consensus algorithm.
Happy Learning 