Consistency and Consensus

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2021-07-18 17:00:03

Welcome to the 10% Smarter newsletter. I’m Brian, a software engineer writing about tech and growing skills as an engineer.

Distributed systems are complex and include many difficult problem to tackle. Fortunately, some techniques have been developed and are widely used in production to deal with these issues in distributed systems. Today, we’ll discuss the relationship between consistency and consensus, and how they are used online services all over the world.

Linearizability is the property that a data object should appear as if there were only one copy of the object, and all operations on object are atomic. Linearizability also guarantees the data will be the most up-to-date on reads and writes of a single object. This however, does not protect against write skew.

Linearizability is used by Apache ZooKeeper, etcd, and Google Chubby. These are lock granting services and are often used to implement distributed locks, leader election and service discovery. They use consensus algorithms to be linearizable.