Changelog

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All notable changes to mem-evoq will be documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

[0.1.1] - 2026-05-15

Fixed

  • Adapter contract: mem_evoq_adapter was returning raw reckon_gater #event{} records to evoq, but the evoq_event_store contract expects #evoq_event{} records (or maps). The mismatch made the adapter unusable when actually wired into evoq — evoq_event_store:read/5 would crash with function_clause inside its event_to_map/1 helper. 0.1.0 worked when called directly in mem-evoq's own tests but failed at the evoq seam.
  • Read paths (read/5,6, read_all/3,4, read_all_global/3, read_by_event_types/3, read_by_tags/3,4) now translate #event{} → #evoq_event{} at the adapter boundary.
  • Subscription delivery now goes through a per-subscription bridge process that translates {events, [#event{}]} → {events, [#evoq_event{}]} before forwarding. subscription_error messages (e.g. integrity violations during catch-up) pass through unchanged. Matches the pattern reckon-evoq uses.

mac and signature are storage-only concerns and are intentionally NOT propagated through the adapter — same as reckon-evoq. Tests that assert on them now go through sys:get_state on the store gen_server.

[0.1.0] - 2026-05-15

Initial release. In-memory event-store adapter for evoq — a reference implementation of the evoq_event_store callback contract, intended for tests, demos, and integration scaffolding without spinning up Khepri/Ra.

Adapter surface

  • mem_evoq_adapter implements the full evoq_event_store callback set: append, read (forward/backward, with optional verify mode), read_all / read_all_global, version, exists, has_events, list_streams, delete, save_snapshot / load_snapshot / list_snapshots / delete_snapshot, subscribe / subscribe_all / unsubscribe.
  • mem_evoq facade: start_store/1,2, stop_store/1, list_stores/0.
  • mem_evoq_registry — ETS-backed StoreId → Pid lookup with monitor-driven cleanup.
  • mem_evoq_store — per-store gen_server holding streams, snapshots, subscribers, and (when enabled) the integrity context.

Write path

  • append/4 honours ?NO_STREAM, ?ANY_VERSION, ?STREAM_EXISTS, and exact-version expected-version semantics matching reckon-db.
  • Cross-stream global ordering via epoch_us microsecond timestamps.

Read path

  • Forward and backward reads slice exact [FromVersion, FromVersion+Count-1] (forward) / [max(0, FromVersion-Count+1), FromVersion] (backward) windows.
  • Out-of-range requests return partial results (no padding, no error). Stream-not-found returns {stream_not_found, StreamId}.

  • Optional read/6 accepting #{verify => skip_legacy | strict | skip_all} for integrity-enabled stores. Backward verification uses the reverse → verify forward → reverse-back trick from reckon-db 2.1.1.

Subscriptions

  • Per-store subscribe / subscribe_all / unsubscribe.
  • Filter taxonomy: by_stream, by_event_type, by_event_pattern, by_tags (with any / all match).
  • from => 0 triggers synchronous catch-up replay before the call returns.
  • Dead-subscriber cleanup via process monitor — subscriptions self-evict on 'DOWN'.

Snapshots

  • Save / load / load-at-version / list / delete.
  • Stream deletion cascades to snapshots.

Tamper resistance (opt-in per store)

  • start_store/2 accepts #{integrity => #{enabled => true, key => Key}} — Key must be exactly 32 bytes. Invalid sizes / malformed maps surface as {error, ...} at start time.
  • Every appended event under an integrity-enabled store carries prev_event_hash (genesis for v0, chain hash of predecessor thereafter) and mac (HMAC-SHA256 via reckon_gater_integrity).
  • Per-stream chain-start watermark recorded on the first append; lazy enablement supports stores switched on mid-life.
  • Read verification: strict fails on legacy events; skip_legacy (default) verifies integrity-bearing events only; skip_all disables verification entirely.
  • Snapshots carry anchor_hash (chain hash of the event at the snapshot's version) + mac. Load recomputes the anchor — a tampered underlying stream surfaces as snapshot_anchor_mismatch even if the tampered event itself has been re-signed with the legitimate key.
  • Subscription catch-up MAC-verifies every event before delivery; violations halt the catch-up with {subscription_error, {integrity_violation, _}}.

Tests

  • 93 EUnit tests across append / read / metadata / read_all_global / subscription / snapshot / integrity / snapshot-integrity surfaces.
  • 6 Common Test cases (test/integration/mem_evoq_integrity_writes_SUITE) mirroring reckon_db_integrity_writes_SUITE.
  • 6 PropEr properties × 100 random runs each (test/prop/prop_mem_evoq).
  • Total: 699 distinct test invocations on rebar3 eunit && rebar3 ct && rebar3 proper.

Out of scope (see README limitations table)

Persistence, clustering / replication, key rotation, per-region keys, vault integration, capability-token-bound writes, scavenging / archive, and reckon-db's full filter taxonomy. For any of these, pair evoq with reckon-evoq + reckon-db.