elixir-otp-patterns

Use OTP patterns like GenServer, Supervisor, and Task to build fault-tolerant concurrent applications. GenServer manages state and handles messages, Supervisor monitors and restarts workers on failure, and Task handles asynchronous workloads. Together they create self-healing systems that isolate failures and maintain reliability.

GenServer is an Elixir abstraction for building stateful, message-driven processes. Implement it by defining callbacks like init, handle_call, and handle_cast to manage initialization, synchronous requests, and asynchronous messages. GenServer enforces lifecycle patterns that prevent common concurrency bugs.

Supervisor strategies define restart policies when workers fail. One-for-one restarts only the failed worker; one-for-all restarts all children; rest-for-one restarts the failed worker and those started after it. Choose based on dependencies between workers to contain failures appropriately.

Use Agent for simple, stateful data that needs get/update operations without complex message handling. Use GenServer when you need rich message handling, timeouts, or complex business logic alongside state. Agent is lighter; GenServer offers more control and observability.

Supervise Tasks through a Supervisor or DynamicSupervisor to ensure failed async work doesn't crash your application. Task-based workers are monitored and restarted on failure, letting you pipeline async workloads safely within your OTP tree.

GenServer enforces timeout handling through the timeout option in callbacks. If a process crashes, its Supervisor detects the failure and applies the configured restart strategy—typically restarting the process to recover. Errors in callbacks are contained and logged.