ytgui / temp

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raft #94

Closed ytgui closed 4 years ago

ytgui commented 5 years ago

https://raft.github.io/ https://raft.github.io/raft.pdf

ytgui commented 4 years ago

Raft

a consensus algorithm, designed to be easy to understand
equivalent to Paxos in fault-tolerance and performance
different to Paxos, Raft has independent subproblems, production ready.

Consensus

multiple servers agreeing on values in fault-tolerant distributed systems
once they reach a decision on a value, that decision is final
consensus algorithms make progress when any majority of their servers is available, and stop making progress if nore servers fail
never return an incorrect result

Consensus typically arises in the context of replicated state machines (多状态机场景), each server has a state machine and a log.
The state machine is the component that we want to make fault-tolerant, such as a hash table.
In client side, server is a single realiable state machine.
A consensus algorithm is used to agree on the commands in the servers' logs.

ytgui commented 4 years ago

Raft

Introduction

Strong Leader: log entries only flow from the leader to other servers.
Leader election: randomized timers to elect leader, resolving conflicts simply and rapidly.
Membership changes: new joint consensus approach allow cluster to continue operating normally during configuration changes.

Replicated state machines problem