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168 records -> docs/decisions/records/<area>/<topic>.md (163 active, 23 dirs) and docs/decisions/archive/<area>/<topic>.md (5 archived). The filename IS the key, so one-active-record-per-key becomes a filesystem property rather than a validator check, and supersession becomes a `git mv`. WHY: the monolith was a concurrency problem before an aesthetic one. A 3,900-line append target made parallel sessions collide -- PR #605 and PR #614 both hit append-vs-append conflicts during routine rebases, and hand-resolving those inside the corpus is exactly the operation the rationale-rewrite guard exists to police. HOW IT IS VERIFIED: a ~170-file diff cannot be meaningfully read, so correctness does not rest on reading it. The parser was taught BOTH formats first, so the body-diff guard parses the old form at the merge-base and the new form at head -- the migration validates itself, no bypass. The proof is a field-level equivalence harness: 168 records before and after, zero lost, zero gained, zero field mismatches, zero rationale bodies differing. Reviewers should scrutinise the harness; it is the actual evidence. What measuring caught that reading would not have: - ~500 lines sit OUTSIDE any record -- decisions.md's lifecycle schema and each topic file's preamble, mostly the only copy. Source files are kept and stripped, never deleted. They also cannot be filed per-area: topic files hold several areas and 4 of 23 areas span several files. - Archive discovery was a non-recursive glob; after the split it found ZERO archived records, surfacing as four bogus "supersedes points to unknown key" errors rather than an obvious failure. - ~32 live docs point into the corpus BY DATE, which the split dangles. Each stripped file now ends with a generated "Records formerly in this file" index, which also rescues the identical breadcrumbs in old issue comments. - decisions.md's "In this file:" list was 97 same-file anchor bullets that the split makes WRONG, not merely stale. Dropped; the generated index replaces them with links that resolve. The equivalence harness now runs against a checked-in FIXTURE, not the live corpus. The earlier version migrated the real tree, which made it a one-shot: the moment the migration landed there was nothing left to move and the tests failed for reasons unrelated to the code. A fixture keeps them testing the SCRIPT rather than the repo's current state. Keys preserved verbatim, warts included: `sched` (12) and `scheduling` (1) remain two directories for one concept. Renaming a key is not a move -- it changes identity, breaks the equivalence proof, and invalidates MemPalace's per-key drawers. Taxonomy normalisation is separate work. refs #610
29 lines
2.3 KiB
Markdown
29 lines
2.3 KiB
Markdown
# Optimistic concurrency — ETag / If-Match / Version (#253, #259, #265, #269)
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Why the replace-all and config-bearing aggregates carry optimistic concurrency, and how the
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contract evolved (including the reversals). The **mechanics** — headers, status codes, the
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recipe — live in `docs/api-conventions.md` §7a–§7c; this file preserves the *decision
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rationale*, relocated from the append-only `docs/decisions.md` at the v26.9.0 consolidation.
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Issue trail: #253 (PR1 infra + PR3 Diff/Scalar fan-out), #259 (stable child identity for
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schedule-item replace), #265 (RFC 7232 If-Match semantics), #269 (non-If-Match force-write +
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cross-editor ETag rotation). Refs #197.
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## Contents
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---
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## Records formerly in this file
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Each record below moved to its own file under `records/` (ersatztv#610); the rationale is
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unchanged. Resolve by **key** — that is the stable identity. A date-based pointer from
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another doc or an old issue comment should land here and then follow the link.
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- 2026-07-11 — #253 PR3: Diff + Scalar concurrency fan-out (Collection / Playout×2 / MultiCollection / RerunCollection) — [`concurrency.diff-scalar-fanout`](records/concurrency/diff-scalar-fanout.md)
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- 2026-07-11 — Optimistic-concurrency contract for replace-all PUTs (#253 PR1: infra + Block reference) — [`concurrency.replace-all-contract`](records/concurrency/replace-all-contract.md)
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- 2026-07-11 — Stable child identity for schedule-item replace (#259, split from #252/#253) — [`concurrency.schedule-item-child-identity`](records/concurrency/schedule-item-child-identity.md)
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- 2026-07-12 (#269 — non-If-Match root writers force-write past a concurrent Version bump) — [`concurrency.force-write-non-ifmatch`](records/concurrency/force-write-non-ifmatch.md)
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- 2026-07-12 — Cross-editor ETag rotation completed for Collection/Playout config siblings (#269) — [`concurrency.etag-rotation-completion`](records/concurrency/etag-rotation-completion.md)
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- 2026-07-12 — If-Match evaluates per RFC 7232: valid-but-non-matching → 412, only grammar violations → 400 (#265) — [`concurrency.ifmatch-rfc7232`](records/concurrency/ifmatch-rfc7232.md)
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- 2026-07-18 — Concurrent same-item add is idempotent, not a 500: catch the unique-violation per provider (#308) — [`concurrency.idempotent-concurrent-add`](records/concurrency/idempotent-concurrent-add.md)
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