Resilience

Core Principles

1. Polly v8 resilience pipelines, not v7 policies — Polly v8 replaced Policy with ResiliencePipeline. Never use PolicyBuilder, Policy.Handle<>(), or ISyncPolicy. The new API is composable, type-safe, and integrates natively with IHttpClientFactory.
2. Configure via AddResilienceHandler, not manual wrapping — For HTTP calls, use Microsoft.Extensions.Http.Resilience which adds pipelines directly to HttpClient via DI. No manual ExecuteAsync wrapping.
3. Compose strategies, don't nest them — A single ResiliencePipeline can chain retry + circuit breaker + timeout. Strategies execute outer-to-inner (first added = outermost). No need for nested try/catch or manual orchestration.
4. Always set timeouts — Every external call needs a timeout. Use Polly's AddTimeout() as the innermost strategy so it applies per-attempt, and optionally an outer timeout for total elapsed time.
5. Instrument everything — Polly v8 emits Metering events and supports TelemetryOptions for OpenTelemetry. Use them to monitor retry rates, circuit breaker state, and timeout frequency.

Patterns

HTTP Client Resilience (Recommended Default)