Invoker Chain

The invoker chain is the execution pipeline for event handlers. Every handler invocation flows through the chain:

Tracer
 └─ Metrics
     └─ RateLimiter (may abort early)
         └─ Idempotency (may skip execution)
             └─ Retry (re-executes on failure)
                 └─ CircuitBreaker (health decisions)
                     └─ DLQ (last resort)
                         └─ Handler

Each invoker has a single responsibility, is stateless or externally backed, and emits its own metrics.

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Table of contents

• Composition
• Retry
• Circuit Breaker
• Rate Limiter
• Idempotency
• Metrics Invoker
• DLQ Invoker
• Error Classification