alkstore/tasks/mem-engine-streams.md at 4aa9023ca4f09d556ff0b71aacf90c313f9f16be

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glm-5.3-flash 5abd351c86 Wave-6 decomposition (mem engine): eleven tasks per the pg-wave rhythm — foundations (crate scaffold, MemStore::new isolation, guarded state core, wake routing, wasm32 gate from birth), seam-tx (the load-bearing tx overlay: eleven staged _tx methods, commit-merge + wake-at-commit — pg-fix-tx-wake's discipline structural from the start, drop = discard trivial, with_tx panic posture), mechanisms mutually parallel (notify-listen close-at-engine-drop/no-replay/never-coalesced; queues = ADR-010 machine driver-free with the equal-jitter curve and opts resolution as ADR-012 §2's third owner; streams log+offsets+trim; locks TTL registry, no busy-path analog), scheduler-outbox (tick/catch-up-64/leadership through the __alkstore_scheduler lock, engine-uniform per ADR-009 §4; outbox over queues with the 60/5/5 seam stamp), integration (suite third StoreFactory column green on host under a current-thread flavor, wasm32 acceptance items, engine-mem.md to implementation-complete), and the review-wave-6 gate (born-pinned audit: conformance read, discharge-map wiring, wasm items, three-way equivalence green, class-1 window discipline). Window riders: suite-harness-current-thread — the wave's one suite-side pre-task, past_stamp_sleep's blocking sleep goes async per review 003's properties.rs:1683 posture note, enabling the current-thread flavor; pg-fix-scheduler-tick-seam — review 003 Finding 1, the cfg(test) transient-fault seam driving the real tick_with_retries through retry-then-success and exhaustion arms (the last uncovered wave-4 hardening arm, sqlite-commit-error-arm pattern). Task hygiene: pg-fix-open-path frontmatter fixed (unquoted 'max_size: 0' colon-space inside the name scalar broke YAML parsing — taskgraph validate had been red one-error since the wave-4 fix-batch decomposition; also restores review-wave-4-fixes' dependency resolution). implementation.md: wave-6 table row → decomposed, task-set listing with the parallelism note (rider + pre-task independent of the mem chain; rider closes before the gate), wave-6 decomposition bullet in the review-rounds record. Docs-only change; verified taskgraph validate (60 tasks, no cycles), cargo fmt --check, cross-reference read

2026-10-10 09:57:01 +00:00

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Description

The streams mechanism over an in-memory event log + per-consumer offset table (engine-mem.md §Mapping the contract, streams row):

StreamHandle surface (ADR-019 §2): publish / publish_with_key (present key must be non-empty → InvalidName), read_since / read_from_consumer (cursor reads, offset ASC, extents clamp empty per ADR-023 §2), save_offset / get_offset (monotone saves — below-checkpoint saves are silent no-ops, Err arm carries Database only), trim_to (delete offset <= horizon, exact-boundary, returns deleted count, negative horizon deletes nothing idempotently, wakes nothing, surviving rows keep offsets, never renumbered), and subscribe (durable consumption: attach, read to tail, resume from saved offset; wake-driven with re-read — the wake substrate delivers at commit; explicit saves only, no auto-checkpoint).
Ordering: engine-assigned monotonically increasing per-stream offsets, global FIFO by offset — the ADR-015 ordering row, mem's own counter (per-stream; absolute values need not equal the SQL engines' — the equivalence rows pin relative order).
StreamEvent shape exactly as pinned (ADR-015 §3): { offset, stream, key, payload, created_at } — created_at is unix-seconds at publish, informational, from the clock accessor. Reads from a trimmed-away region resume at the horizon's first remaining row.
Keyed publish rides the tx overlay (staged publish_with_key_tx landed in mem-engine-seam-tx); this task's non-tx forms, receiver, and trim live here.
Receiver close arms (ADR-021 §5): recv()'s Err carries Database only (payloads cross raw; Codec at payload_as<T>); close is terminal — the one close path is engine drop (the notify-listen task's close arm, realized identically); no reconnection concept (the pg stays-open-across- reconnect row is absent from mem's column).

Acceptance Criteria

Full StreamHandle surface over the in-memory log + per-consumer offsets
The ADR-015 properties unit-pinned: global FIFO, immutable never-renumbered offsets (gaps legal post-trim), exact-boundary trim semantics (reads resume at horizon; saved sub-horizon offsets stay valid; trim wakes nothing), monotone save composition (direct + receiver forms interleave)
Key round-trips exactly (None vs Some); empty-Some-key rejected at every entry point
Extent/offset numeric-domain guards at entry — pinned
cargo check --target wasm32-unknown-unknown -p alkstore-mem clean; workspace gates green

References

docs/architecture/core-contract.md §streams
docs/architecture/decisions/015-streams-depth.md; 019-mechanism-handle-surfaces.md §2/§6; 021 §5; 023 §2
docs/architecture/engine-mem.md §Mapping the contract (streams row)
tasks/pg-engine-streams.md (the structural twin's task of record)

Notes

To be filled by implementation agent

Summary

To be filled on completion

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