Distributed Systems

Summary: Computer systems where components are distributed across multiple machines and communicate through networks to appear as a single coherent system. These systems coordinate through message passing to achieve common goals while managing challenges of network latency, failures, and consistency.

Overview

Distributed systems are architectures where multiple independent computers work together across a network to solve problems that would be difficult or impossible for a single machine. The key characteristic is that components are physically separated but logically unified, requiring sophisticated coordination mechanisms to maintain system coherence.

The fundamental challenge in distributed systems is achieving coordination despite the inherent unreliability of networks—systems must handle partial failures, message delays, and network partitions while maintaining correctness and availability. This creates the famous trade-offs described by the CAP theorem: consistency, availability, and partition tolerance cannot all be guaranteed simultaneously.

Modern distributed systems power everything from web services and databases to cloud computing platforms and Multi-Agent Systems. They enable horizontal scaling, fault tolerance, and geographic distribution of services, but require careful design to manage complexity.

Key Details

Core Principles:

  • Transparency: Hide distribution complexity from users and applications
  • Scalability: Support growth in users, resources, and geographic distribution
  • Reliability: Continue operating despite component failures
  • Consistency: Maintain coherent data across all nodes
  • Concurrency: Handle simultaneous operations efficiently

Communication Patterns:

  • Message passing through network protocols
  • Remote procedure calls (RPCs) for service invocation
  • Event-driven architectures for loose coupling
  • Publish-subscribe systems for broadcast communication

Failure Models:

  • Crash failures (components stop responding)
  • Omission failures (messages lost or delayed)
  • Byzantine failures (components behave arbitrarily)
  • Network partitions (connectivity loss between groups)

Consistency Models:

  • Strong consistency (all nodes see same data simultaneously)
  • Eventual consistency (convergence after updates cease)
  • Weak consistency (no guarantees about when data converges)
  • Causal consistency (preserves causally related operations)

Coordination Mechanisms:

  • Consensus algorithms (Paxos, Raft) for agreement
  • Leader election for centralized coordination
  • Distributed locking for mutual exclusion
  • Vector clocks for ordering events

Relationships

Sources