Tianyi Cui
9126697d87
Add a SQLite SessionPersistence backend (node:sqlite), a SECOND implementation built to prove the abstract seam + the shared runPersistenceContract suite are genuinely backend-agnostic. Each SessionEvent maps 1:1 onto an events row (session_id, seq, type, time, data); append is an INSERT inside a transaction asserting the contiguous-seq contract; the mutable SessionSummary lives in the sessions metadata row. It satisfies the SAME contract semantics as the JSONL backend, expressed over rows instead of file bytes: - Lazy materialization: create() records intent in memory; no row until the first append (a never-appended session is absent from has()/list() via a materialized flag set inside the first append transaction). - Crash-tail-on-load: load() returns events only through the last complete turn/end and deletes the uncommitted tail; a seq gap in the committed region makes the session unloadable. - Transactional append: a mid-batch failure (a UNIQUE seq collision from a concurrent writer) rolls back entirely, keeping the cursor truthful. Like the JSONL backend it is also the write-path plugin (session/event → buffer → session/flush drain, onCreated seed/adopt/collision handling, HMR seeding, dispose-to-quiescence). The package runs the shared runPersistenceContract suite plus SQLite-specific tests (transaction rollback, crash-tail cut, schema version, HMR adoption). Docs flip every "SQLite is future/deferred" reference (ADR 0016, architecture.md, the persistence module doc + README) to "implemented; the contract holds both backends to identical semantics".
34 lines
3.4 KiB
Markdown
34 lines
3.4 KiB
Markdown
# @deepseek-ai/dsh-session-persistence
|
|
|
|
The abstract durable session-persistence seam (`ctx.sessionPersistence`). Defines WHAT a persistence backend does — durably store, reload, list, and update sessions — without saying HOW. Mirrors the `dsh-bash` capability-seam template ([ADR 0009](../../docs/adr/0009-capability-seams.md)): an abstract service here, a concrete implementation in a sibling package, consumers that inject the interface.
|
|
|
|
The persisted unit IS the existing `SessionEvent` (event-sourced model — the log is the single source of truth), so there is no parallel "persisted message" type. Metadata that is NOT replayable conversation state (format version, cwd, lineage) travels separately as `SessionMeta`, owned by `dsh-session` and re-exported here.
|
|
|
|
## Service API (`ctx.sessionPersistence`)
|
|
|
|
| Method | Contract |
|
|
|---|---|
|
|
| `create(meta): Promise<void>` | Register a new session's metadata. MAY defer the physical write until the first `append` (lazy materialization). |
|
|
| `append(id, events): Promise<void>` | Durably persist a batch (from the `session/flush` drain). Append-only; first event `seq` == stored next-seq after any repair; rejects non-JSON-serializable data naming the offending type. |
|
|
| `load(id): Promise<{ meta; events }>` | Reload meta + log up to the last complete `turn/end`; events contiguous (`events[i].seq === i`); rejects a mid-log gap/parse error or unknown `version`. |
|
|
| `list(): Promise<SessionMeta[]>` | Lightweight listing from metadata, no full-log parse. |
|
|
| `has(id)` / `delete(id)` | Existence / removal. A zero-event lazily-materialized session is absent from `has`/`list`. |
|
|
| `update(id, summary): Promise<void>` | Update mutable `SessionSummary` fields without touching the append-only log. |
|
|
|
|
## Invariants every backend must honor
|
|
|
|
- **Append-only.** Committed events (at or below a flushed `turn/end`) are never rewritten. The only exception is the one-time truncation-repair of a never-committed crash tail on the first `append` after a `load`.
|
|
- **Contiguous seq.** `load` rejects a `seq` gap/parse error in the MIDDLE of the log; `append`'s first `seq` must equal the stored next-seq.
|
|
- **JSON-serializable data.** `append` rejects non-serializable `event.data`; backends snapshot each event when buffering (the live `session.events` object is mutable).
|
|
- **Durability.** `append` returns only once the batch is durable.
|
|
|
|
## Testing backends
|
|
|
|
Import `runPersistenceContract` from `tests/contract.ts` and call it with a factory that yields a fresh, empty backend plus a teardown. Every backend is held to the same append-only / contiguous-seq / lazy-materialization / serializability semantics; a backend's own spec adds implementation-specific tests (crash repair, path sanitization) on top.
|
|
|
|
Two backends run this suite: `dsh-session-persistence-jsonl` (append-only file log) and `dsh-session-persistence-sqlite` (`node:sqlite`, each `SessionEvent` one row `(session_id, seq, type, time, data)`). Both passing the same contract is the proof that the seam is genuinely backend-agnostic — lazy materialization, crash-tail-on-load, and contiguous-seq hold identically over file bytes and over a transactional store.
|
|
|
|
## Metadata types
|
|
|
|
Re-exported from `dsh-session`: `SessionHeader` (immutable: `version`, `id`, `createdAt`, `cwd?`, `parentSession?`), `SessionSummary` (mutable: `updatedAt`, `title?`, `firstPrompt?`), `SessionMeta` (their intersection).
|