# Changelog

All notable changes to reckon-db will be documented in this file.

The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).

## [Unreleased]

## [1.3.2] - 2026-02-21

### Fixed

- **pg scope process dies silently**: `pg:start_link(?RECKON_DB_PG_SCOPE)` was called
  from `reckon_db_app:start/2`, creating an unsupervised pg process linked only to the
  application master. When it died, no supervisor restarted it, silently breaking ALL
  event delivery (emitter workers join pg groups for subscription routing). Moved pg scope
  startup into `reckon_db_sup:init/1` as the first supervised child with
  `restart => permanent`, ensuring it is always restarted on failure.

### Added

- `reckon_db_pg_scope_SUITE` integration tests verifying pg scope supervision,
  automatic restart after crash, and full event delivery after scope restart.

## [1.3.0] - 2026-02-20

### Fixed

- **Leader detection in single mode**: `reckon_db_node_monitor` used a one-shot leader
  check in single mode that never rescheduled. If Ra leader election hadn't completed
  by the first check, the LeaderWorker never activated and emitter pools never started.
  Fixed to retry until leader is detected, then stop polling (no leadership changes in
  single-node mode).
- **Node monitor placement**: Moved `reckon_db_node_monitor` from `cluster_sup` (cluster
  mode only) to `system_sup` (all modes). The node monitor must run in single mode too
  to detect Ra leader and activate leader responsibilities.
- **Supervisor strategies**: Changed `notification_sup` and `leader_sup` from `one_for_one`
  to `rest_for_one`. If `leader_sup` crashes, `emitter_sup` must restart to prevent stale
  emitter pools running without leader coordination. If `leader_tracker` crashes,
  `leader_worker` must restart to re-establish dependency on tracking infrastructure.

### Added

- **Subscription health monitor** (`reckon_db_subscription_health`): Periodic health
  checks (default 60s) that detect and clean up stale subscriptions (dead subscriber),
  orphaned emitter pools (pool without subscription), and missing emitter pools
  (subscription without pool). Only performs cleanup on the Ra leader node. Includes
  on-demand `health_check/1` API returning a health report map.
- **Dead subscriber cleanup in emitter**: When an emitter worker detects its subscriber
  PID is dead during event delivery, it now asynchronously stops the emitter pool
  (matching ex-esdb's `send_or_kill_pool` pattern). Previously dead subscribers
  accumulated silently.
- **Emitter autostart integration tests**: New CT suite
  `reckon_db_emitter_autostart_SUITE` with 13 end-to-end tests covering leader
  activation, subscription lifecycle, event delivery, dead subscriber cleanup,
  and health monitor operation.

## [1.2.7] - 2026-02-18

### Fixed

- **Persistence worker crash on undefined options**: `get_persistence_interval/1` called
  `maps:get/3` on the `options` field of `store_config`, which crashed with `{badmap, undefined}`
  when `options` was not explicitly set. Fixed by adding a guard clause for `is_map(Options)`
  and a fallback clause that returns the default persistence interval. Also set the default
  value of `options` in the `store_config` record to `#{}` (empty map) to prevent this class
  of bug in other code paths.

## [1.2.6] - 2026-02-13

### Fixed

- **Subscription id not populated**: `subscribe/5` created the `#subscription{}` record
  without setting the `id` field, leaving it as `undefined`. The subscription key was
  computed and used for Khepri storage and trigger registration, but the subscription
  record passed to `notify_created` (and thus to the leader_tracker and emitter pool)
  still had `id = undefined`. This caused emitter workers to join pg group
  `{StoreId, undefined, emitters}` while Khepri triggers broadcast to
  `{StoreId, CorrectKey, emitters}` — a different group. Events were silently dropped
  because no emitters were found in the broadcast group. Fixed by setting
  `Subscription#subscription{id = Key}` before passing to downstream consumers.

## [1.2.5] - 2026-02-13

### Fixed

- **Stream subscription filter path mismatch**: `by_stream/1` was stripping the category
  prefix from stream IDs (e.g., `<<"test$delivery-001">>` became `<<"delivery-001">>`),
  creating Khepri trigger filters that never matched stored events. This caused ALL
  stream-based subscriptions to silently fail — triggers never fired, subscribers never
  received events. Fixed to use the full stream ID in the filter path.
- **Event type filter record matching**: `by_event_type/1` used a map pattern
  (`#{event_type => Type}`) to match stored events, but events are stored as `#event{}`
  records (tuples). Map patterns cannot match records. Fixed to use proper record pattern
  matching with `#event{event_type = Type, _ = '_'}`.

### Added

- **Subscription delivery integration tests**: New CT suite
  `reckon_db_subscription_delivery_SUITE` with 5 end-to-end tests verifying the full
  subscribe → append → trigger → emitter → deliver pipeline.

## [1.2.4] - 2026-02-13

### Fixed

- **Subscription Filter Error Handling**: `create_filter/2` errors no longer crash the
  gateway worker. Invalid stream names (e.g., missing `$` separator) now return
  `{error, {invalid_filter, Reason}}` instead of propagating to `khepri_evf:wrap/1`
  which caused a `function_clause` crash.
- **Gateway Worker Resilience**: `handle_cast` for `save_subscription` now matches
  the result and logs a warning on failure instead of crashing. Previously, a single
  invalid subscription could crash the worker and lose all 28+ pending subscription
  messages in its queue.

## [1.2.3] - 2026-02-06

### Fixed

- **Subscription Filter Types**: Fixed `create_filter/2` function_clause error
  - Added support for gater-style subscription types: `by_stream`, `by_event_type`,
    `by_event_pattern`, `by_event_payload`, `by_tags`
  - Maintains backward compatibility with evoq-style types
  - Required for reckon_evoq_adapter type translation through the gater layer

## [1.2.2] - 2026-02-01

### Documentation

- **Event Envelope Documentation**: Improved event structure documentation
  - Added note about evoq event envelope in `guides/event_sourcing.md`
  - Documented metadata standardization (required vs optional fields)
  - Cross-referenced evoq Event Envelope Guide
  - Clarified simplified vs full envelope formats

## [1.2.1] - 2026-01-21

### Fixed

- **Documentation**: Corrected asset paths for hexdocs SVG rendering
  - Changed `../assets/` to `assets/` in all guides

## [1.2.0] - 2026-01-21

### Added

- **Distributed Store Registry**: Cluster-wide store discovery using pg groups
  - `reckon_db_store_registry` GenServer with pg-based distributed membership
  - Automatic store announcement/unannouncement on start/stop
  - Cross-node store visibility via broadcast mechanism
  - `list_stores/0` - List all stores in the cluster
  - `get_store_info/1` - Get detailed info about a specific store
  - `list_stores_on_node/1` - List stores on a specific node
  - 11 new unit tests for store registry
  - Gateway worker calls registry directly (no facade layer)

## [1.1.1] - 2026-01-21

### Added

- **Documentation**: Added Event Sourcing Paradigms guide to hexdocs
  - Entity-Centric (Traditional DDD)
  - Relationship-Centric (DCB - Dynamic Consistency Boundaries)
  - Process-Centric (Dossier metaphor with tags)

## [1.1.0] - 2026-01-21

### Added

- **Tag-Based Querying**: Cross-stream event queries using tags
  - `read_by_tags/4` - Query events by tags across all streams
  - Support for `any` (union) and `all` (intersection) matching modes
  - Tags field added to event records and storage
  - 15 new unit tests for tag filtering
  - Tags are for QUERY purposes only, NOT for concurrency control

### Changed

- **Dependencies**: Updated reckon_gater from `~> 1.0.3` to `~> 1.1.0` for tags support

## [1.0.3] - 2026-01-19

### Changed

- **Dependencies**: Updated reckon_gater from exact `1.0.0` to `~> 1.0.3` to include
  critical double-wrapping bugfix

## [1.0.2] - 2026-01-09

### Fixed

- **Documentation**: Minor documentation improvements

## [1.0.0] - 2026-01-03

### Changed

- **Stable Release**: First stable release of reckon-db under reckon-db-org
- All APIs considered stable and ready for production use
- Updated Dockerfile with correct package names (reckon_db)
- Fixed guide asset paths for hexdocs compatibility

## [0.4.6] - 2025-12-26

### Fixed

- **Dependency conflict**: Removed direct `ra` dependency (khepri provides it).
  Updated to `reckon_db_gater ~> 0.6.5` which removed stale ra from its lock file.

## [0.4.5] - 2025-12-26

### Fixed

- **Dependency conflict**: Updated `ra` dependency from exact `2.16.12` to `~> 2.17.1`
  to resolve conflict with `reckon_db_gater ~> 0.6.4` which requires `ra ~> 2.17.1`

## [0.4.4] - 2025-12-22

### Added

- **Configuration Guide**: Comprehensive configuration documentation
  - Store configuration options (data_dir, mode, pool sizes)
  - Health probing configuration
  - Consistency checking and persistence intervals
  - Erlang (sys.config) and Elixir (config.exs) examples
  - Complete development/staging/production examples
  - Performance tuning recommendations
  - Telemetry events reference

## [0.4.3] - 2025-12-22

### Added

- **Gateway Worker Handlers**:
  - `delete_stream` - Delete streams via gateway
  - `read_by_event_types` - Native Khepri type filtering via gateway
  - `get_subscription` - Get subscription details including checkpoint

These handlers support the erl-evoq-esdb adapter improvements.

## [0.4.2] - 2025-12-22

### Added

- **Cluster Consistency Checker** (`reckon_db_consistency_checker.erl`):
  - Split-brain detection via membership consensus verification
  - Leader consensus verification across all cluster nodes
  - Raft log consistency checks (term and commit index)
  - Quorum status monitoring with margin calculation
  - Four status levels: `healthy`, `degraded`, `split_brain`, `no_quorum`
  - Configurable check intervals (default: 5000ms)
  - Status change callbacks for alerting
  - Telemetry events: `[reckon_db, consistency, ...]`

- **Active Health Prober** (`reckon_db_health_prober.erl`):
  - Fast failure detection via active probing (default: 2000ms intervals)
  - Three probe types: `ping`, `rpc`, `khepri`
  - Configurable failure threshold (default: 3 consecutive failures)
  - Node status tracking: `healthy`, `suspect`, `failed`, `unknown`
  - Recovery detection with callbacks
  - Telemetry events: `[reckon_db, health, ...]`

- **Cluster Consistency Guide** (`guides/cluster_consistency.md`):
  - Split-brain problem explanation and prevention strategies
  - Consistency checker usage and configuration
  - Health prober integration patterns
  - Quorum management and recovery procedures
  - Circuit breaker and load balancer integration examples

- **Architecture Diagrams** (SVG):
  - `assets/consistency_checker.svg` - Consistency checker architecture
  - `assets/split_brain_detection.svg` - Split-brain detection flow
  - `assets/health_probing.svg` - Health probing timeline

### Tests

- 35 unit tests for consistency checker
- 37 unit tests for health prober
- All 72 new tests passing

## [0.4.1] - 2025-12-22

### Added

- **Server-Side Documentation Guides**:
  - `guides/temporal_queries.md` - Point-in-time queries, timestamp filtering, cluster behavior
  - `guides/scavenging.md` - Event lifecycle, archival backends, safety guarantees
  - `guides/causation.md` - Causation/correlation tracking, graph building, DOT export
  - `guides/stream_links.md` - Derived streams, filter/transform patterns
  - `guides/schema_evolution.md` - Schema registry, version-based upcasting, validation
  - `guides/memory_pressure.md` - Pressure levels, callbacks, integration patterns
  - `guides/storage_internals.md` - Khepri paths, version padding, cluster replication

- **Architecture Diagrams** (SVG):
  - `assets/temporal_query_flow.svg` - Temporal query processing flow
  - `assets/scavenge_lifecycle.svg` - Event lifecycle state machine
  - `assets/causation_graph.svg` - Causation chain visualization
  - `assets/stream_links.svg` - Stream linking architecture
  - `assets/schema_upcasting.svg` - Schema version upcasting flow
  - `assets/memory_levels.svg` - Memory pressure level thresholds
  - `assets/khepri_paths.svg` - Khepri storage path structure

### Changed

- **Documentation Improvements**:
  - Replaced ASCII diagrams with professional SVG graphics
  - `snapshot_recovery.svg` - Performance comparison visualization
  - `event_fanout.svg` - Multi-subscriber event delivery diagram
  - Updated `rebar.config` ex_doc with new guides organized into Core Concepts, Advanced Features, and Operations sections

## [0.4.0] - 2025-12-22

### Added

- **Enterprise Edition NIFs**: High-performance Rust NIFs with pure Erlang fallbacks
  - Community Edition (hex.pm) uses pure Erlang implementations
  - Enterprise Edition (git + Rust) gets 5-100x speedups for specific operations
  - Automatic fallback detection via `persistent_term`

- **esdb_crypto_nif** (Phase 1):
  - `nif_base58_encode/1` - Fast Base58 encoding for DIDs
  - `nif_base58_decode/1` - Fast Base58 decoding
  - Uses Bitcoin alphabet, ~5x faster than pure Erlang

- **esdb_archive_nif** (Phase 2):
  - `nif_compress/1,2` - Zstd compression with configurable level
  - `nif_decompress/1` - Zstd decompression
  - `nif_compress_batch/1,2` - Batch compression for multiple items
  - `nif_decompress_batch/1` - Batch decompression
  - ~10x faster than zlib, better compression ratios

- **esdb_hash_nif** (Phase 3):
  - `nif_xxhash64/1,2` - 64-bit xxHash with optional seed
  - `nif_xxhash3/1` - Modern xxHash3 (SIMD optimized)
  - `nif_partition_hash/2` - Hash to partition number
  - `nif_stream_partition/3` - Combined store+stream routing
  - `nif_partition_hash_batch/2` - Batch hashing for bulk ops
  - `nif_fnv1a/1` - FNV-1a for small keys
  - `nif_fast_phash/2` - Drop-in phash2 replacement

- **esdb_aggregate_nif** (Phase 3):
  - `nif_aggregate_events/2` - Bulk fold with tagged value semantics
  - `nif_sum_field/2` - Vectorized sum accumulation for numeric fields
  - `nif_count_where/3` - Count events matching field condition
  - `nif_merge_tagged_batch/1` - Batch map merge with tagged values
  - `nif_finalize/1` - Unwrap tagged values ({sum, N}, {overwrite, V})
  - `nif_aggregation_stats/1` - Event statistics (counts, unique fields)

- **esdb_filter_nif** (Phase 3):
  - `nif_filter_events/2` - Filter events by compiled predicate
  - `nif_filter_count/2` - Count matching events without collecting
  - `nif_compile_predicate/1` - Pre-compile filter predicates
  - `nif_partition_events/2` - Partition events by predicate (matching/non-matching)
  - `nif_first_match/2` - Find first matching event
  - `nif_find_all/2` - Find all matching events with indexes
  - `nif_any_match/2`, `nif_all_match/2` - Boolean aggregate predicates

- **esdb_graph_nif** (Phase 4):
  - `nif_build_edges/1` - Build edge list from event causation relationships
  - `nif_find_roots/1`, `nif_find_leaves/1` - Find root/leaf nodes
  - `nif_topo_sort/1` - Topological sort (Kahn's algorithm via petgraph)
  - `nif_has_cycle/1` - Detect cycles in causation graph
  - `nif_graph_stats/1` - Calculate node/edge/depth statistics
  - `nif_to_dot/1,2` - Generate Graphviz DOT format
  - `nif_has_path/2` - Check if path exists between nodes
  - `nif_get_ancestors/2`, `nif_get_descendants/2` - BFS path finding

### Changed

- **Build profiles**:
  - Added `enterprise` profile with Rust NIF compilation hooks
  - Added `enterprise_test` profile for testing with NIFs
  - Build with `rebar3 as enterprise compile` to enable NIFs

### Documentation

- Updated README with Enterprise/Community edition information
- Added NIF function documentation with academic references

## [0.3.1] - 2025-12-20

### Changed

- **Version padding**: Increased from 6 to 12 characters (`?VERSION_PADDING` macro)
  - Previous: 999,999 events per stream max (~2.7 hours at 100 events/sec)
  - Now: 999,999,999,999 events per stream max (~317 years at 100 events/sec)
  - Supports long-running neuroevolution, IoT, and continuous event streams

### Fixed

- **EDoc errors**: Removed backticks and markdown from EDoc comments (breaks hex.pm docs)

## [0.3.0] - 2025-12-20

### Added

- **Capability-Based Security** (`esdb_capability_verifier.erl`, `esdb_revocation.erl`):
  - Server-side verification of UCAN-inspired capability tokens
  - Ed25519 signature verification using issuer's public key from DID
  - Token expiration and not-before time validation
  - Resource URI pattern matching (exact, wildcard suffix, prefix)
  - Action permission checking with wildcard support
  - Token revocation management (ETS-based, gossip integration planned)
  - Issuer revocation for compromised identities
  - Content-addressed token IDs (CIDs) for revocation tracking
  - Comprehensive unit tests (13 verifier tests + 6 revocation tests)

This completes Phase 3 of the decentralized security implementation.
Client-side token creation is in reckon-gater, server-side verification is here.

### Changed

- **Documentation**: Replaced ASCII diagrams with SVG in README and guides

### Fixed

- **README API documentation**: Fixed incorrect function signatures
  - Subscriptions: Added missing `unsubscribe/3`, `get/2` functions
  - Snapshots: Fixed `load/3` → `load_at/3`, `delete/3` → `delete_at/3`, added `exists/2`, `exists_at/3`
  - Aggregator: Completely rewrote section - was showing non-existent API (`foldl/4`, `foldl_from_snapshot/4`)
- **guides/snapshots.md**: Fixed `load/3` → `load_at/3`, `delete/3` → `delete_at/3`, rewrote aggregator example
- **guides/cqrs.md**: Fixed subscription key usage in emitter group join
- **guides/subscriptions.md**: Fixed invalid map access syntax
- **guides/event_sourcing.md**: Fixed aggregator foldl signature (takes events list, not store/stream)

## [0.2.0] - 2024-12-19

### Added

- **End-to-end tests**: 24 comprehensive e2e tests for gater integration:
  - Worker registration (4 tests)
  - Stream operations via gater (9 tests)
  - Subscription operations (4 tests)
  - Snapshot operations (4 tests)
  - Load balancing (3 tests)
- **Subscriptions**: Added `ack/4` function for acknowledging event delivery

### Fixed

- **Gateway worker API compatibility**:
  - `get_version` now handles integer return correctly
  - Snapshot operations use correct function names (`save`, `load_at`, `delete_at`)
  - Subscription unsubscribe uses correct 3-arg version
- **Header conflicts**: Added `ifndef` guards for `DEFAULT_TIMEOUT` macro

### Changed

- **reckon-gater integration**: Updated to work with gater's pg-based registry (replacing Ra)
- **Test counts**: Now 72 unit + 53 integration + 24 e2e = 149 total tests

## [0.1.0] - 2024-12-18

### Added

- Initial release of reckon-db, a BEAM-native Event Store built on Khepri/Ra
- Event stream operations:
  - `append/4,5` - Write events with optimistic concurrency control
  - `read/5` - Read events from streams (forward/backward)
  - `get_version/2` - Get current stream version
  - `exists/2` - Check if stream exists
  - `list_streams/1` - List all streams in store
  - `delete/2` - Soft delete streams
- Subscription system:
  - Stream subscriptions - events from specific streams
  - Event type subscriptions - events by type across streams
  - Pattern subscriptions - wildcard stream matching
  - Payload subscriptions - content-based filtering
- Snapshot management:
  - `save/5` - Save aggregate state snapshots
  - `load/2,3` - Load latest or specific version snapshots
  - `list/2` - List all snapshots for a stream
  - `delete/3` - Delete old snapshots
- Aggregation utilities:
  - `foldl/4` - Fold over events with accumulator
  - `foldl_from_snapshot/4` - Fold starting from latest snapshot
- Cluster support:
  - UDP multicast discovery (LibCluster gossip compatible)
  - Automatic Khepri/Ra cluster formation
  - Node monitoring and failover
  - Leader election and tracking
- Emitter pools for high-throughput event delivery
- Partitioned writers for concurrent stream writes
- BEAM telemetry integration with configurable handlers
- Comprehensive test suite (72 unit + 53 integration tests)
- Educational guides:
  - Event Sourcing fundamentals
  - CQRS patterns
  - Subscriptions usage
  - Snapshots optimization

### Dependencies

- Khepri 0.17.2 - Raft-based distributed storage
- Ra 2.16.12 - Raft consensus implementation
- Telemetry 1.3.0 - BEAM telemetry for observability