generated from john/python-template
84 lines
4.0 KiB
Markdown
84 lines
4.0 KiB
Markdown
# Error Handling Policy (Version 4)
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This policy defines active V4 error taxonomy, translation boundaries, and retry semantics.
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## Error Categories
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| Category | Meaning | Typical Origin | User Treatment |
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| :--- | :--- | :--- | :--- |
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| `validation` | Input payload/selection is invalid | UI form parsing, service validators | Inline correction guidance |
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| `not_found` | Target record is missing | ID lookup in service layer | Non-blocking warning or redirect |
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| `conflict` | State prevents requested action | lifecycle transitions, duplicate semantic keys | Explain required precondition |
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| `external` | Provider/network dependency failure | OpenRouter/provider adapter | Retry path and evidence retained |
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| `timeout` | Provider call exceeded configured bound | worker/provider client timeout | Retry path and bounded messaging |
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| `internal` | Unexpected local failure | unhandled service/runtime faults | Safe generic message + diagnostics capture |
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## Translation Boundaries
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- **Provider layer:** raise provider-scoped exceptions with provider context; do not emit UI text.
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- **Service layer:** map raw exceptions into domain-aware categories and preserve causal chain.
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- **UI/API layer:** convert category to user-safe message with contextual action guidance.
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## Decision Context
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### Why taxonomy is category-based (not exception-class-based)
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- Categories encode operator-facing recovery semantics (fix input, retry later, investigate internal failure) independent of low-level exception type.
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- This keeps retry and messaging behavior consistent even when provider/client libraries change.
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### Why page-level failure is isolated
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- Multi-page archival documents often contain a mix of readable and degraded pages.
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- Isolating failures to page scope preserves successful results and avoids all-or-nothing loss when one page fails.
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- Aggregate job status then communicates overall outcome (`transcribed`, `partial_success`, `failed`) without hiding page detail.
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### Why retries append evidence instead of mutating rows
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- Retry operations are new observations, not corrections of history.
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- Appending attempts preserves forensic traceability, timing history, and provider variability analysis.
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- Projection updates remain explicit user/workflow decisions, separate from immutable evidence.
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## Job and Page Failure Semantics
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### Page-Level (`JobSource`)
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- `pending` -> `transcribed` when attempt succeeds.
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- `pending` -> `failed` when attempt fails terminally.
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- `pending` -> `cancelled` on job cancellation before processing.
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### Job-Level (`Job`)
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- `transcribed` when all pages transcribe successfully.
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- `partial_success` when mixed success/failure outcomes exist.
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- `failed` when no page transcribes successfully.
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## Retry and Retranscription Rules
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1. Failed/cancelled pages may be re-queued through retranscription workflows.
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2. Retry attempts must append new `ExecutionAttempt` rows; prior evidence remains immutable.
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3. Selecting a better candidate must update projection pointers, not mutate historical attempt rows.
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## Logging and Diagnostics Rules
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1. Persist sufficient attempt error metadata (`error_category`, `error_message`, transport evidence) for post-hoc analysis.
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2. Avoid leaking stack traces or local paths into user-facing message envelopes.
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3. Preserve causal exception chains for internal diagnostics.
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## Operator Recovery Guidance
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- **validation/conflict:** correct input or state and retry manually.
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- **external/timeout:** allow bounded retries and keep prior attempt evidence visible.
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- **internal:** stop automatic retries, surface a safe message, and inspect diagnostics with correlation context.
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## UI Messaging Contract
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- User-visible errors must be actionable, bounded, and category-consistent.
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- Multi-page jobs must show partial outcomes instead of collapsing into a single opaque failure.
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- Recovery actions (`retry`, `retranscribe`, `edit input`) must be offered where available.
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## Cross-Reference
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- [Error Handling invariant](../invariant/error_handling.md)
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- [System Requirements](requirements_v4.md)
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- [Data Model](schema_v4.md)
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