234 lines
11 KiB
Markdown
234 lines
11 KiB
Markdown
# Memory Service
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**Package:** `@nexusai/memory-service`
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**Location:** `packages/memory-service`
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**Deployed on:** Mini PC 1 (192.168.0.81)
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**Port:** 3002
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## Purpose
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Responsible for all reading and writing of long-term memory. Acts as the
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sole interface to both SQLite and Qdrant — no other service accesses these
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stores directly. On episode creation, automatically triggers entity and
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relationship extraction and embeds results into Qdrant.
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## Dependencies
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- `express` — HTTP API
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- `better-sqlite3` — SQLite driver
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- `@qdrant/js-client-rest` — Qdrant vector store client
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- `dotenv` — environment variable loading
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- `@nexusai/shared` — shared utilities and constants
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## Environment Variables
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| Variable | Required | Default | Description |
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|---|---|---|---|
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| PORT | No | 3002 | Port to listen on |
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| SQLITE_PATH | Yes | — | Path to SQLite database file |
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| QDRANT_URL | No | http://localhost:6333 | Qdrant instance URL |
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| EMBEDDING_SERVICE_URL | No | http://localhost:3003 | Embedding service URL |
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| EXTRACTION_URL | No | http://localhost:11434 | Ollama URL for entity extraction |
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| EXTRACTION_MODEL | No | qwen2.5:3b | Ollama model used for entity extraction |
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## Internal Structure
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```
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src/
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├── db/
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│ ├── index.js # SQLite connection + initialization + migrations
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│ ├── schema.js # Table definitions, indexes, FTS5, triggers
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│ ├── projects.js # Project CRUD functions
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│ └── summaries.js # Summary CRUD functions
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├── episodic/
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│ └── index.js # Session + episode CRUD, FTS search, embedding write path
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├── semantic/
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│ └── index.js # Qdrant collection management, upsert, search, delete
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├── entities/
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│ ├── index.js # Entity + relationship CRUD (upsert, mention tracking)
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│ └── extraction.js # Automatic entity + relationship extraction via qwen2.5:3b
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├── graph/
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│ └── index.js # Knowledge graph traversal (neighborhood queries, recursive CTE)
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└── index.js # Express app + all route definitions
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```
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## SQLite Schema
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Eight core tables:
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- **sessions** — top-level conversation containers. Fields: `external_id`, `name`, `project_id`, `metadata`
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- **episodes** — individual exchanges (user message + AI response) tied to a session
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- **entities** — named things the system learns about (people, places, concepts, etc.). Fields include `mention_count`, `confidence`, `source`, `last_seen_at`
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- **relationships** — directional labeled links between entities (`from_id`, `to_id`, `label`). Fields include `mention_count`, `notes`
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- **entity_episodes** — join table linking entities to the episodes where they were extracted. Used for provenance and orphan cleanup
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- **summaries** — condensed episode groups for efficient context retrieval
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- **projects** — named groupings of sessions with `name`, `description`, `colour`, `icon`, `isolated`, `notes`, `system_prompt`
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### Migrations
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Schema changes that cannot use `CREATE TABLE IF NOT EXISTS` are applied as
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idempotent migrations in `db/index.js` at startup:
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```js
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try { db.exec(`ALTER TABLE sessions ADD COLUMN name TEXT`); } catch {}
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try { db.exec(`ALTER TABLE sessions ADD COLUMN project_id INTEGER REFERENCES projects(id)`); } catch {}
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try { db.exec(`CREATE INDEX IF NOT EXISTS idx_sessions_project ON sessions(project_id)`); } catch {}
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try { db.exec(`ALTER TABLE projects ADD COLUMN isolated INTEGER NOT NULL DEFAULT 0`); } catch {}
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try { db.exec(`ALTER TABLE projects ADD COLUMN notes TEXT`); } catch {}
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try { db.exec(`ALTER TABLE projects ADD COLUMN system_prompt TEXT`); } catch {}
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// Knowledge graph columns:
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try { db.exec(`ALTER TABLE entities ADD COLUMN mention_count INTEGER NOT NULL DEFAULT 1`) } catch {}
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try { db.exec(`ALTER TABLE entities ADD COLUMN confidence REAL NOT NULL DEFAULT 1.0`) } catch {}
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try { db.exec(`ALTER TABLE entities ADD COLUMN source TEXT NOT NULL DEFAULT 'extraction'`) } catch {}
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try { db.exec(`ALTER TABLE entities ADD COLUMN last_seen_at INTEGER`) } catch {}
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try { db.exec(`ALTER TABLE relationships ADD COLUMN mention_count INTEGER NOT NULL DEFAULT 1`) } catch {}
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try { db.exec(`ALTER TABLE relationships ADD COLUMN notes TEXT`) } catch {}
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```
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`entity_episodes` is defined in `schema.js` itself (not a migration) since it is a new table.
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New migrations are always appended — never modify the schema file for existing tables since `ALTER TABLE` cannot use `IF NOT EXISTS`.
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### FTS5 Full-Text Search
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An `episodes_fts` virtual table enables keyword search across all episodes.
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Three triggers (`episodes_fts_insert`, `episodes_fts_update`, `episodes_fts_delete`)
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keep the FTS index automatically in sync with the episodes table.
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### SQLite Configuration
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- `journal_mode = WAL` — non-blocking reads during writes
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- `foreign_keys = ON` — enforces referential integrity and cascade deletes
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- PRAGMAs set via `db.pragma()`, not `db.exec()`
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### Dynamic Updates
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Both `updateSession` and `updateProject` build their `SET` clause dynamically
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from only the fields passed — prevents partial updates from overwriting fields
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that weren't touched.
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`updateProject` allowlist:
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```js
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const allowed = ['name', 'description', 'colour', 'icon', 'isolated', 'notes', 'system_prompt'];
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```
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## Qdrant / Semantic Layer
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Three Qdrant collections are initialized on service startup via `semantic.initCollections()`:
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| Collection | Purpose |
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| `episodes` | Embeddings for individual conversation exchanges |
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| `entities` | Embeddings for named entities |
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| `summaries` | Embeddings for condensed episode summaries |
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All collections use **768-dimension vectors** with **Cosine similarity**,
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matching `nomic-embed-text` via Ollama. Vector size and distance metric are
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defined in `@nexusai/shared` — not hardcoded here.
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`initCollections()` iterates `Object.values(COLLECTIONS)` and creates any
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collection that doesn't already exist at startup — all three collections are
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guaranteed to exist before any requests are handled.
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Each collection exposes upsert, search (with optional Qdrant filter), and
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delete operations. The `wait: true` flag is used on all writes.
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## Embedding Write Path
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When a new episode is created:
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1. Episode saved to SQLite synchronously — response returned immediately
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2. User message + AI response combined: `User: ...\nAssistant: ...`
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3. Text sent to embedding service (`POST /embed`)
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4. Vector upserted into `episodes` Qdrant collection with payload `{ sessionId, createdAt }`
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This step is **fire-and-forget** — if embedding fails, the episode is still
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saved and searchable via FTS. The error is logged but not surfaced.
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> The Qdrant payload stores `sessionId` (the internal integer ID). See
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> `memory-isolation.md` for how project-level filtering works.
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## Entity Layer
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Entities and relationships use upsert semantics with composite unique
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constraints to prevent duplicates:
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- `UNIQUE(name, type)` on entities — conflict increments `mention_count` and updates `last_seen_at`
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- `UNIQUE(from_id, to_id, label)` on relationships — conflict increments `mention_count` and preserves existing `notes`
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- `ON DELETE CASCADE` on relationship foreign keys
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After each episode is saved, `extraction.js` automatically extracts named
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entities **and relationships** from the conversation using `qwen2.5:3b` on
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Ollama — fire-and-forget. Each saved entity is also linked to the episode
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via the `entity_episodes` join table.
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> For full details on the extraction pipeline and JSON format, see `entity-extraction.md`.
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> For the knowledge graph traversal layer, see `knowledge-graph.md`.
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## Knowledge Graph Layer
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`src/graph/index.js` provides SQLite-based graph traversal over the entities
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and relationships tables. Two functions are exposed via HTTP:
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- **`getNeighborhood(entityId, depth)`** — recursive CTE traversal, bidirectional, returns `{ nodes, edges }`
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- **`getEntityNeighbors(entityIds[])`** — bulk 1-hop traversal for orchestration context assembly
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> For design rationale, traversal queries, and integration with orchestration, see `knowledge-graph.md`.
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## Summaries Layer
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Session summaries are generated by `orchestration-service/src/services/summarization.js`
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after each episode write and stored here via `POST /summaries`. The memory
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service is responsible only for CRUD — generation logic lives in orchestration.
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> For full details on trigger conditions, prompt format, cumulative updates,
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> and ChatML token stripping, see `summarization.md`.
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## Delete Behaviour (SQLite + Qdrant consistency)
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SQLite cascades handle relational cleanup, but Qdrant is a separate store and
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must be cleaned explicitly. Each delete path that removes embedded rows also
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removes the corresponding vectors:
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| Delete | SQLite effect | Qdrant cleanup |
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| `DELETE /episodes/:id` | Row removed | `semantic.deleteEpisode(id)` — vector by point ID |
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| `DELETE /sessions/by-external/:id` | Session + episodes cascade-deleted | `semantic.deleteEpisodesBySession(id)` — **payload-filter** delete on `sessionId` |
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| `DELETE /entities/:id` | Row removed, relationships cascade | `semantic.deleteEntity(id)` — vector by point ID |
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All three Qdrant deletes are **fire-and-forget** with error logging, matching
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the fire-and-forget write path — a Qdrant failure logs but does not fail the
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delete.
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The session path uses a **payload-filter** delete (matching on the `sessionId`
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field in the vector payload) rather than enumerating episode point IDs. This
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matters because the SQLite cascade has already removed the episode rows by the
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time cleanup runs, so there are no IDs left to enumerate — the filter deletes
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by payload regardless. It also cleans up any pre-existing orphans for that
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session as a side effect.
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> **Not cleaned on session delete:** entity vectors. Entities are shared across
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> sessions and projects (`UNIQUE(name, type)` is global), so deleting one
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> session must not remove entities that other sessions still reference. Entity
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> vector lifecycle is tied to explicit entity deletion and the (planned) memory
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> consolidation / orphan-cleanup pass.
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> **Historical orphans:** vectors orphaned by session deletes *before* this
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> cleanup existed are not removed retroactively. A one-time sweep (scroll the
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> `episodes` collection, delete points whose `sessionId` no longer exists in
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> SQLite) clears them.
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## Project Delete Behaviour
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Deleting a project runs as a transaction — it first nulls out `project_id`
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on all assigned sessions, then deletes the project. This avoids a foreign
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key constraint failure since `sessions.project_id` has no `ON DELETE` rule:
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```js
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const doDelete = db.transaction(() => {
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db.prepare(`UPDATE sessions SET project_id = NULL WHERE project_id = ?`).run(id);
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db.prepare(`DELETE FROM projects WHERE id = ?`).run(id);
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});
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```
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For all HTTP endpoints, see `api-routes.md`. |