Chapter 11
Paxos
Use two consensus-building phases to reach safe consensus even when nodes disconnect.
Problem
When multiple nodes share state, they often need to agree between themselves on a particular value. With Leader and Followers, the leader decides and passes its value to the followers. But if there is no leader, then the nodes need to determine a value themselves. (Even with a leader-follower, they may need to do this to elect a leader.)
A leader can ensure that replicas safely acquire an update by using Two-Phase Commit, but without a leader we can have competing nodes attempt to gather a Majority Quorum. This process is further complicated because any node may fail or disconnect. A node may achieve ...
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