Error Handling#

Consistent errors reduce support load and on-call pain. Design a taxonomy, stable codes, safe user messaging, and operator visibility—without leaking secrets or stack traces to clients.

When to Offer This Workflow#

Trigger conditions:

• Inconsistent HTTP status codes and response bodies
• Retry storms or duplicate side effects from naive retries
• Logs that cannot be tied to user-visible failures

Initial offer:

Use six stages: (1) classify errors, (2) map to transport, (3) user messaging, (4) retries & idempotency, (5) observability, (6) client SDKs & DX). Confirm REST/GraphQL/gRPC and sync/async patterns.

---

Stage 1: Classify Errors#

Goal: Distinguish validation, authentication, authorization, not found, conflict, rate limit, dependency failure, and internal bugs.

Exit condition: Table or enum of codes with owning team and meaning.

---

Stage 2: Map to Transport#

Goal: Correct HTTP 4xx/5xx; GraphQL errors with extensions; gRPC status codes; optional RFC 7807 Problem Details for JSON APIs.

---

Stage 3: User Messaging#

Goal: Actionable copy for end users; opaque support reference id; no internal hostnames, SQL fragments, or stack traces in client responses.

---

Stage 4: Retries & Idempotency#

Goal: Retry only safe or idempotent operations; exponential backoff with jitter; align with idempotency keys on writes.

---

Stage 5: Observability#

Goal: Structured logs with error.code, trace_id, user_id (where allowed); metrics by error class; alerts on error-rate SLO burn.

---

Stage 6: Client SDKs & DX#

Goal: Typed errors in SDKs; documented recovery; map codes to user-facing strings in apps consistently.

---

Final Review Checklist#

• Taxonomy and ownership defined
• Transport mapping correct and consistent
• User-safe messages with correlation ids
• Retry policy matches idempotency story
• Logs and metrics wired for ops

Tips for Effective Guidance#

• Separate expected validation errors from unexpected 500s in dashboards.
• Pair with idempotency for write paths and queues.

Handling Deviations#

• Mobile offline: queue with explicit user-visible sync state.