Go

The Writer Starvation Problem In the readers preference solution, we saw how continuous readers can starve writers. The writers preference solution fixes this by giving writers priority. Key idea: When a writer is waiting, no new readers are allowed to start, even if other readers are currently reading. Real-World Need for Writer Priority Some systems need writer priority: Databases with critical updates (billing, inventory) Real-time systems (sensor updates must not be delayed) Logging systems (log writes can’t be delayed) Configuration systems (updates must propagate quickly) Leader election (state changes need priority) The Solution Go’s sync.RWMutex uses readers preference, so we need to implement writer preference manually using additional synchronization: ...

From Unbounded to Bounded In the previous article, we explored the unbounded buffer pattern where the queue could grow infinitely. This works until you run out of memory! The bounded buffer adds a crucial constraint: maximum queue size. This introduces backpressure - when the buffer is full, producers must wait for consumers to catch up. Why Bounded Buffers Matter Bounded buffers appear everywhere in production systems: TCP sliding windows (flow control) HTTP/2 stream flow control (prevents overwhelm) Message queue limits (RabbitMQ, Kafka partition limits) Thread pool queues (bounded task queues) Rate limiters (token buckets with finite capacity) Circuit breakers (limit concurrent requests) The key benefit: Bounded buffers provide natural backpressure and prevent resource exhaustion. ...

Building production-grade services requires more than just functionality-they need resilience, graceful degradation, and the ability to handle failures without crashing. In this post, we’ll build a robust logging service that demonstrates these principles using Go’s context package and proper error handling. The Problem Imagine your application sends logs to a remote logging service. What happens when: The logging service is slow or unresponsive? Network issues cause delays? The logging service crashes entirely? Without proper safeguards, your entire application could hang, crash, or become unresponsive just because logging failed. Logging should never bring down your application. ...

The Sleeping Barber Problem The Sleeping Barber is a classic synchronization problem proposed by Edsger Dijkstra in 1965. It elegantly demonstrates resource management, waiting, and signaling in concurrent systems. The Scenario A barbershop has: 1 barber 1 barber chair N waiting room chairs The rules: If no customers, the barber sleeps When a customer arrives: If barber is sleeping → wake him up If barber is busy → sit in waiting room (if space available) If waiting room is full → leave When barber finishes a customer → check waiting room Real-World Applications This pattern appears in many systems: ...

The Classic Dining Philosophers Problem The Dining Philosophers problem is one of the most famous concurrency problems, introduced by Edsger Dijkstra in 1965. It beautifully illustrates the challenges of resource sharing and deadlock in concurrent systems. The Setup: Five philosophers sit around a circular table. Between each pair of philosophers is a single fork (5 forks total). Each philosopher needs two forks to eat - one from their left and one from their right. ...

The Elevator Problem The Elevator Problem is a classic scheduling and optimization challenge that models how multiple elevators coordinate to serve passengers efficiently. It demonstrates load balancing, scheduling algorithms, optimization trade-offs, and decentralized coordination. Unlike many concurrency problems, it focuses on real-time decision-making and multi-objective optimization. The Scenario A building has: N elevators moving between floors M floors Passengers arriving at random floors with random destinations Call buttons (up/down) on each floor Destination buttons inside each elevator The goals: ...

The Bully Election Algorithm The Bully Algorithm, proposed by Hector Garcia-Molina in 1982, is a classic leader election algorithm for distributed systems. It’s called “bully” because the highest-numbered process always wins and “bullies” the others into accepting it as leader. The Scenario A distributed system needs a coordinator: N nodes in a network Each node has a unique ID (priority) One node must be elected as leader When the leader fails, a new leader must be elected Rule: The node with the highest ID wins The protocol: ...

The Fairness Problem We’ve seen two extremes: Readers preference: Writers can starve Writers preference: Readers can starve The fair solution ensures no starvation - everyone gets served in the order they arrive. The Solution: FIFO Ordering Key idea: Use a queue to serve requests in arrival order. This prevents both reader and writer starvation. Arrival Order: R1, R2, W1, R3, R4, W2 Execution: R1+R2 → W1 → R3+R4 → W2 (batch) (excl) (batch) (excl) Consecutive readers can still batch together, but writers don’t get skipped! ...

The Byzantine Generals Problem The Byzantine Generals Problem, proposed by Leslie Lamport, Robert Shostak, and Marshall Pease in 1982, is one of the most important problems in distributed systems. It addresses the challenge of achieving consensus when some participants may be faulty or malicious. The Scenario Byzantine army divisions surround a city: N generals command their divisions They must coordinate: attack or retreat They communicate via messengers Some generals are traitors who send conflicting messages Goal: All loyal generals must agree on the same plan The challenge: ...

The Readers-Writers Problem The Readers-Writers problem is fundamental in concurrent systems where data is shared between multiple threads: Readers: Can access data simultaneously (read-only, no conflicts) Writers: Need exclusive access (modifications can’t overlap) The challenge: Maximize concurrency while maintaining data integrity. Real-World Applications This pattern is everywhere: Databases: SELECT queries (readers) vs UPDATE/INSERT (writers) Caching: Cache reads vs cache updates Configuration: Reading config vs reloading config File systems: Multiple readers, exclusive writes Web servers: Read sessions vs update sessions Readers Preference Solution In this variant, readers get priority: ...