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olp/lib
9b66326e72 feat+test: D58 — server.mjs streaming singleflight wiring (ADR 0005 Amendment 8, issue #16) (#37)
* feat+test: D58 — server.mjs streaming singleflight wiring (ADR 0005 Amendment 8 §§7,11,12, issue #16)

Second of three D-days for v1.x roadmap #1. D57 landed the cache-layer
primitive (cacheStore.getOrComputeStreaming); D58 wires it into the
streaming branch of server.mjs and adds the X-OLP-Streaming-Inflight
header. D59 closes issue #16 + polishes README known-limitations.

## What

server.mjs — replaced the streaming branch (formerly the peek+spawn
pattern at lines 1138-1327) with cacheStore.getOrComputeStreaming(...):
- tryAcquireSpawn moves INSIDE sourceFactory closure (§7). Only first
  caller acquires; attached joiners share the slot. releaseSpawn lives
  in the source generator try/finally so it fires once on source
  completion / error / abort.
- CONCURRENCY_LIMIT thrown by the factory triggers fallthrough to the
  buffered path (preserving today's behaviour); any other pre-stream
  factory error surfaces a 502.
- X-OLP-Streaming-Inflight: source | attached header per §11 (cache_hit
  role omits — X-OLP-Cache: hit already says it). The §11 'solo' value
  is deferred to a future amendment — observable only post-stream via
  the streaming_inflight_source_done log event's attached_count.
- auditCtx.cache_status: 'miss' for source, 'streaming_attached' for
  joiners, 'hit' for the TTL-race cache_hit branch.
- res.on('close', () => stream.return?.()) propagates client disconnect
  into the tee's attachedClients accounting (§9). Note: Node 25 emits
  'close' on ServerResponse, NOT on IncomingMessage — empirically
  verified in test 28g.
- Cache writes now happen inside the cache layer's tee task on source
  completion (§4). Server still issues cacheStore.delete on stop-less
  exhaustion to preserve D16 truncated-not-cached invariant — the cache
  layer is IR-agnostic and writes accumulatedChunks unconditionally;
  the IR-aware server deletes the entry if no stop chunk was observed.
- The pre-cache-store-acquire and matching releaseSpawn-on-503 branches
  are gone — they were vestigial once the factory owns acquire+release.

lib/audit.mjs — JSDoc cache_status enum extended with 'streaming_attached'.
Free-form string at the wire (no schema validator on append); the JSDoc
is the source of truth for the consumer enum.

test-features.mjs Suite 28 — 7 HTTP integration tests:
- 28a single SSE request (source role + cache populated + second request
  → X-OLP-Cache: hit)
- 28b 2 concurrent identical SSE → one spawn, source + attached roles,
  identical chunk sequences delivered
- 28c TOCTOU regression — pre-populated cache + 2 concurrent → both hit
  buffered replay path, no streaming branch entry, no
  X-OLP-Streaming-Inflight header
- 28d mid-stream join — late joiner receives accumulated burst + live tail
- 28f one-of-N disconnect — source NOT aborted; survivor completes
- 28g ALL clients disconnect → source aborted; no cache write; subsequent
  request gets fresh source spawn
- 28h CONCURRENCY_LIMIT fallthrough — factory throws at maxConcurrent=1;
  buffered path's chain-exhausted 502 surfaces

(28e backpressure deferred to Suite 27g unit-level coverage.)

## Scope

server.mjs + lib/audit.mjs + test-features.mjs. Untouched: cache/store.mjs
(D57 frozen), provider plugins, fallback engine, IR. CHANGELOG and
package.json bump fires at D59 close.

## Authority

- docs/adr/0005-cache-cross-provider.md Amendment 8 §§7, 8, 9, 11, 12
- docs/v1x-roadmap.md #1
- GitHub issue #16 (TOCTOU window; closed in D59)
- ADR 0002 Amendment 6 (D38 tryAcquireSpawn/releaseSpawn semantics that
  §7 now invokes inside the sourceFactory closure)

## Test count

615 → 622 (+7 D58 integration tests). Local: 622/622 pass.

## Iron Rule 10 follow-up notes for the reviewer

- res.on('close') vs req.on('close'): switched to res after empirical
  verification (28g fails on req under Node 25). Comment in code.
- Cache-layer write + server-layer delete for stop-less exhaustion is
  cosmetically inconsistent with streaming_inflight_source_done's
  cache_written: true log. Functionally correct; flagged for future
  amendment.
- 'solo' header value deferred — would need trailer mechanics or
  post-stream emission.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

* fix: D58 reviewer follow-ups — P2-1 (audit-query gauge drift) + P2-2 (stop-less HTTP test)

Fold-in for D58 PR #37 fresh-context opus reviewer findings (APPROVE
WITH MINOR — 0 P0/P1, 4 P2). P2-3 (`isFirst` unused) and P2-4 (`solo`
not emitted) are design-acceptable per ADR 0005 Amendment 8 §11 and
left as-is.

P2-1 — `lib/audit-query.mjs` gauge reconciliation. `aggregateRequests`
and `cacheHitRateWindow` previously counted `streaming_attached` rows
in `total` / `pe.total` without contributing to hit/miss/bypass
numerators, breaking the invariant that the cache_status breakdown
should sum to the total. Added an explicit `streaming_attached` field
to both the global return shape and the `by_provider` shape; the
counter is excluded from `hit_rate` numerator AND denominator (joiners
did not hit a literal cache so they don't belong in either side of
the ratio). Test count is unchanged for D49 suites — they only
assert presence + non-negative + reconciliation invariants that the
new field preserves; if a test asserted exact value equality on a
fixture with NO streaming_attached rows, the new field defaults to 0
and the assertion still passes.

P2-2 — Suite 28 stop-less HTTP coverage gap. Test 28i fires an SSE
request to a fake provider whose source generator returns WITHOUT a
{type:"stop"} chunk; asserts (a) the synthetic truncation marker
appears in the body (D26 F19 in-band signal), (b) [DONE] terminator
follows, (c) a subsequent identical request triggers a fresh spawn
(cache was NOT populated by the truncated stream). Pins the D58
`cacheStore.delete` path at server.mjs:1344-1346 end-to-end.

622 → 623 (+1 D58 follow-up test). 623/623 pass locally.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

---------

Co-authored-by: dtzp555 <dtzp555@gmail.com>
Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>
2026-05-25 20:59:54 +10:00
..