Patterns of Distributed Systems

Problem

The Write-Ahead Log pattern is used to recover state after a server crashes and restarts. But a write-ahead log is not enough to provide availability in case of server failure. If a single server fails, then clients won’t be able to function until the server restarts. To get a more available system, we can replicate the log on multiple servers. Using Leader and Followers the leader replicates all its log entries to a Majority Quorum of followers. Now, should the leader fail, a new leader can be elected, and clients can mostly continue to work with the cluster as before. But there are still a couple things that ...