Write-Ahead Log (WAL): What and How it works?
How does WAL provide resiliency to Kafka, Cassandra & Zookeeper?
Write-ahead logging is a key principle in distributed systems. It is extensively used in databases, consensus algorithms, and event-streaming platforms.
Its role is to guarantee data durability and recovery during system crashes or failures.
It ensures that state changes in data are safely preserved by logging them as commands in an append-only format, rather than requiring the entire data structure to be saved to disc.
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This article will explore what problems Write-Ahead Logging addresses, how it works, and real-world systems that leverage it, including ZooKeeper, etcd(Raft), Kafka, and Cassandra.
What Problem Does WAL Solve?
In distributed systems, multiple nodes or servers must maintain a consistent state. However, they often encounter challenges like system crashes, power outages, or network failures.
