Distributed Systems

Overview

Distributed Systems are teams of computers working together. The Cloud is a distributed system.

The core idea is Scalability. A single computer has limits. A thousand computers can do anything. But coordinating them is a nightmare.

A model in which components located on networked computers communicate and coordinate their actions by passing messages.

The Orchestra: One musician is easy to manage. An orchestra needs a conductor (or a very good protocol) to stay in sync.
The Two Generals Problem: Two generals on opposite hills need to attack at the same time. They can only send messengers through the enemy valley. How can they be 100% sure the other got the message? (Spoiler: They can’t).

Google Search: It’s not one computer; it’s data centers full of them.
Blockchain: A distributed ledger where everyone agrees on the truth without a central authority.
BitTorrent: Peer-to-peer file sharing.

Misconception: The network is reliable.
- Correction: The Fallacies of Distributed Computing: The network is reliable, latency is zero, bandwidth is infinite… all lies.
Misconception: It’s just “more computers.”
- Correction: It introduces new classes of bugs (Race Conditions, Partial Failures). “A distributed system is one in which the failure of a computer you didn’t even know existed can render your own computer unusable.” (Leslie Lamport).