# Distributed Failure Recovery

> Partial failure, timeouts, retries, deduplication, fencing, repair, anti-entropy, and disaster recovery.

Canonical: https://learn.significanthobbies.com/curriculum/concepts/distributed-failure-recovery

Partial failure, timeouts, retries, deduplication, fencing, repair, anti-entropy, and disaster recovery.

- Difficulty: core
- Tracks: Distributed Systems

## Mental model

In a distributed system, failure is ambiguous. Recovery needs bounded retries, unique operation identity, stale-writer fencing, repair mechanisms, and tested restore objectives. Scope: this card owns correctness under partial failure — operation identity, fencing a stale writer, repair and anti-entropy, and tested restore objectives. What target you are recovering TO is `reliability-fault-tolerance`; the caller-side backoff policy is `retries-and-circuit-breakers`.



## Primary sources

- [The Network is Reliable (Bailis & Kingsbury)](https://aphyr.com/posts/288-the-network-is-reliable) (doc)
- [Gray Failure: The Achilles' Heel of Cloud-Scale Systems (HotOS '17)](https://www.microsoft.com/en-us/research/publication/gray-failure-achilles-heel-cloud-scale-systems/) (doc)
- [Partitions for Everyone! — Kyle Kingsbury (Strange Loop 2013)](https://www.youtube.com/watch?v=EOlw6dlxXU0) (video)
- [Simple Testing Can Prevent Most Critical Failures (OSDI '14)](https://www.usenix.org/conference/osdi14/technical-sessions/presentation/yuan) (paper)
- [Jepsen: etcd and Consul (Kyle Kingsbury)](https://aphyr.com/posts/316-jepsen-etcd-and-consul) (article)
- [Site Reliability Engineering — Addressing Cascading Failures](https://sre.google/sre-book/addressing-cascading-failures/) (doc)
- [Jepsen Analyses](https://jepsen.io/analyses) (doc)

## Practice

### Design exercise: Distributed Failure Recovery

Partial failure, timeouts, retries, deduplication, fencing, repair, anti-entropy, and disaster recovery. Implement designOutline() returning non-empty values for: failureDetection, duplicateControl, repairPath. Each value must name a concrete mechanism or decision.

**Expected evidence:** A design outline with failureDetection, duplicateControl, repairPath plus an explicit failure mode or trade-off.

## Review prompts

- What is a fencing token, and which failure does it stop that a lease timeout alone does not?

## Build evidence

- **Synthesize: Distributed Systems** — Reason about coordination, data placement, logs, durable workflows, consistency, and recovery under partial failure. Produce one working system, benchmark, or evidence-backed design that integrates the path.

## Prerequisites

- [Distributed Workflows & Temporal](https://learn.significanthobbies.com/curriculum/concepts/distributed-workflows-temporal)

## Related concepts

- [Distributed Workflows & Temporal](https://learn.significanthobbies.com/curriculum/concepts/distributed-workflows-temporal)

## Learning paths

- [12-Week Distributed Systems](https://learn.significanthobbies.com/curriculum/roadmaps/distributed-systems-12w)