refactor(session-persistence): extract a shared write coordinator
The JSONL and SQLite backends were byte-identical (or same-algorithm) for ALL of their write-path orchestration — the four maps (states/buffers/chains/inits), installWritePath, initFor, onCreated's four adoption cases, flush, drain, serialize, adopt/adoptLivePrefix, assertVersion, and the create/append/load/ has/delete skeletons. Only the storage primitives (write bytes vs INSERT rows) differed, so every fix landed twice. Extract that orchestration into a PersistenceCoordinator in the seam package. Each backend composes one (new PersistenceCoordinator(ctx, this)), implements a small PersistenceBackend hook interface (loadStored, loadLive, appendBatch, commitRepair, deleteStored, list, optional close), and delegates its six public service methods to it. Composition, not inheritance — a backend exposes only the hooks, can't reach the coordinator's private state, and the public SessionPersistence API is unchanged so a third-party backend may still implement it directly. The crash-repair torn-tail token is OPAQUE: the coordinator computes the synthetic closers (it owns interruptedTurnClosers) but only tests `tornMarker !== undefined` and round-trips it to commitRepair, never inspecting it (JSONL = byte offset, SQLite = seq). loadStored vs loadLive stay distinct so HMR adoption is cwd-scoped (a same-id log at a different cwd is a collision, not a resume). appendBatch carries meta so lazy-materialize + first-batch commit atomically (no separate materialize hook). Tests: the duplicated orchestration tests (adoption, HMR, collision, dispose-drain, crash-tail) move into one runCoordinatorContract suite run once per backend (memory + jsonl + sqlite) via hook fixtures; per-backend specs keep only storage mechanics. A through-coordinator torn-tail test per real backend keeps the commitRepair-with-marker branch covered under the 100% gate. Net -112 lines (the dedup outweighs the new coordinator + shared suite); 100% coverage; backends shrank ~1200 lines of duplicated churn. Migrates the write-coordinator RFC proposed -> implemented.
This commit is contained in:
Tianyi Cui
13 files changed
+1879
-1991
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@@ -1,19 +1,18 @@
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/**
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* SQLite durable session-persistence backend (`@deepseek-ai/dsh-session-persistence-sqlite`).
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*
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* A SECOND {@link SessionPersistence} implementation, built to validate that
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* the abstract seam + the shared `runPersistenceContract` suite are genuinely
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* A SECOND {@link SessionPersistence} implementation, built to validate that the
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* abstract seam + the shared `runPersistenceContract` suite are genuinely
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* backend-agnostic: the same append-only / contiguous-seq / lazy-materialization
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* / interrupted-turn-close-on-load semantics the JSONL backend expresses over
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* file bytes, expressed here over `node:sqlite` rows. Each `SessionEvent` maps
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* 1:1 onto a row `(session_id, seq, type, time, data)`; `append` is an INSERT
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* inside a transaction that asserts the contiguous-seq contract.
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* 1:1 onto a row `(session_id, seq, type, time, data)`.
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*
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* Like the JSONL backend it is also the write-path plugin: it installs the
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* `session/event` → buffer → `session/flush` drain, persists a fork's seed once
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* on `session/created`, keeps a per-session write cursor so a resumed session
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* never re-appends stored events, and seeds existing live sessions on apply
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* (HMR does not replay `session/created`).
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* Like the JSONL backend it supplies ONLY the storage primitives (the
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* {@link PersistenceBackend} hooks below — INSERT/DELETE/SELECT inside
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* transactions); all the write-path orchestration lives in the backend-agnostic
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* {@link PersistenceCoordinator} this class composes. The six public
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* {@link SessionPersistence} methods delegate to the coordinator.
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*
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* @module @deepseek-ai/dsh-session-persistence-sqlite
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*/
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@@ -24,9 +23,9 @@ import { DatabaseSync } from 'node:sqlite'
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import { mkdir } from 'node:fs/promises'
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import { dirname, resolve } from 'node:path'
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import {
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SessionPersistence, assertSerializable, seedCoversPrefix,
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SessionPersistence, PersistenceCoordinator,
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type PersistenceBackend, type StoredPrefix,
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} from '@deepseek-ai/dsh-session-persistence'
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import { interruptedTurnClosers } from '@deepseek-ai/dsh-session'
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import type { Session, SessionEvent, SessionId, SessionHeader } from '@deepseek-ai/dsh-session'
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import {
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openDatabase, rowToMeta, scanRows, type EventRow, type SessionRow,
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@@ -44,55 +43,36 @@ export interface Config {
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path: string
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}
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/** Backend bookkeeping for a session id (NOT the live Session object). */
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interface SessionState {
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meta: SessionHeader
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/** Next seq to write — equals the number of committed events. */
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cursor: number
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/** Whether the session has at least one persisted event (materialized). */
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materialized: boolean
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/** The live Session that owns this state (collision detection); see onCreated. */
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owner?: Session
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}
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async function settledErrors(promises: Iterable<Promise<unknown>>): Promise<unknown[]> {
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const settled = await Promise.allSettled([...promises])
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const errors: unknown[] = []
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for (const result of settled) {
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if (result.status === 'rejected') errors.push(result.reason)
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}
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return errors
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}
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/**
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* The SQLite persistence backend. Load as a plugin; it registers as
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* `ctx.sessionPersistence` and installs the write-path listeners.
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* `ctx.sessionPersistence` and (via the coordinator) installs the write-path
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* listeners. Its torn-tail marker is the seq to delete from.
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*/
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export class SessionPersistenceSqlite extends SessionPersistence {
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export class SessionPersistenceSqlite extends SessionPersistence implements PersistenceBackend<number> {
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static inject = ['sessions']
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static Config: z<Config> = z.object({
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path: z.string().required(),
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})
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/**
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* Backend label for the coordinator's dispose diagnostics. Intentionally
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* shadows cordis `Service.name` (set to `'sessionPersistence'` by the base);
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* see the JSONL backend for why this does not affect service resolution.
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*/
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override readonly name = 'session-persistence-sqlite'
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private db!: DatabaseSync
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private ready: Promise<void>
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/** Backend bookkeeping keyed by session id (NOT the live Session object). */
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private states = new Map<string, SessionState>()
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/** Write-behind buffers keyed by the live Session (write path). */
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private buffers = new Map<Session, SessionEvent[]>()
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/** Per-session serialization chain (keyed by session id). */
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private chains = new Map<string, Promise<unknown>>()
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/** Per-session init promise (onCreated), keyed by the LIVE Session object. */
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private inits = new Map<Session, Promise<void>>()
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private coordinator: PersistenceCoordinator<number>
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constructor(ctx: Context, public config: Config) {
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super(ctx)
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// Open the database asynchronously (the parent directory may need creating);
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// every backend op awaits `ready` first. Opening synchronously in the ctor
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// would force a sync mkdir and block plugin apply.
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// every hook awaits `ready` first. Opening synchronously would force a sync
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// mkdir and block plugin apply.
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this.ready = this.openDb(config.path)
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this.installWritePath()
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this.coordinator = new PersistenceCoordinator<number>(this.ctx, this)
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}
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private async openDb(path: string): Promise<void> {
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@@ -105,229 +85,156 @@ export class SessionPersistenceSqlite extends SessionPersistence {
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}
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}
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// --- SessionPersistence backend surface (all serialized per session id) ---
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// --- SessionPersistence service surface (delegated to the coordinator) ---
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create(meta: SessionHeader): Promise<void> {
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const snapshot: SessionHeader = { ...meta }
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return this.serialize(snapshot.id, () => this.createCore(snapshot))
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return this.coordinator.create(meta)
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}
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private async createCore(meta: SessionHeader): Promise<void> {
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append(id: SessionId, events: readonly SessionEvent[]): Promise<void> {
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return this.coordinator.append(id, events)
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}
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load(id: SessionId): Promise<{ meta: SessionHeader; events: SessionEvent[] }> {
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return this.coordinator.load(id)
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}
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has(id: SessionId): Promise<boolean> {
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return this.coordinator.has(id)
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}
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delete(id: SessionId): Promise<void> {
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return this.coordinator.delete(id)
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}
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// `list` is BOTH the public service method and the PersistenceBackend hook —
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// one method (the SELECT below). The coordinator adds no orchestration for
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// listing, so routing it through the coordinator would just recurse. Defined
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// once, in the "PersistenceBackend hooks" section.
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/**
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* The per-session init promises, exposed for white-box tests that await a
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* specific session's onCreated (there is no public API to await one init).
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*/
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get inits(): Map<Session, Promise<void>> {
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return this.coordinator.inits
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}
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// --- PersistenceBackend hooks (the SQLite storage primitives) ---
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/** Read a stored prefix by id (ids are globally unique — no scope to scan). */
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loadStored(id: SessionId): Promise<StoredPrefix<number> | undefined> {
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return this.readPrefix(id)
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}
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/** Read a stored prefix; `cwd` is ignored (the id is globally unique in SQLite). */
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loadLive(id: SessionId, _cwd: string | undefined): Promise<StoredPrefix<number> | undefined> {
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return this.readPrefix(id)
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}
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/**
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* Read a session's row + ordered events into a {@link StoredPrefix}. The
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* torn-tail marker is the seq from which a never-committed tail must be deleted
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* (`scanRows` already returns it as `number | undefined`).
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*/
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private async readPrefix(id: SessionId): Promise<StoredPrefix<number> | undefined> {
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await this.ready
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if (this.states.has(meta.id)) {
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throw new Error(`session "${meta.id}" already exists in this backend`)
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}
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if (this.rowFor(meta.id) !== undefined) {
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throw new Error(`session "${meta.id}" already has a persisted row; load/resume it instead of creating`)
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}
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// Lazy: record intent in memory only. No row until the first append, so an
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// abandoned (never-appended) session leaves nothing behind and stays absent
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// from has()/list().
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this.states.set(meta.id, { meta, cursor: 0, materialized: false })
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const row = this.rowFor(id)
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if (row === undefined) return undefined
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const meta = rowToMeta(row)
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const eventRows = this.db
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.prepare('SELECT seq, type, time, data FROM events WHERE session_id = ? ORDER BY seq')
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.all(id) as unknown as EventRow[]
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const { preserved, tornFrom } = scanRows(eventRows)
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return { meta, events: preserved, ...tornFrom !== undefined ? { tornMarker: tornFrom } : {} }
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}
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// `async` so the synchronous validate/clone below reject (not throw) per the
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// Promise<void> contract — callers use `await expect(...).rejects`.
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async append(id: SessionId, events: readonly SessionEvent[]): Promise<void> {
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// Validate serializability BEFORE cloning so a bad event surfaces the typed
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// "non-JSON-serializable" error rather than an opaque DataCloneError from
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// structuredClone. Then deep-snapshot the batch HERE, before the op waits
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// behind the per-session chain: a caller that passes a live array (e.g.
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// session.events) and mutates it — OR mutates an event inside it — before
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// the op runs would otherwise have those changes persisted, or advance the
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// cursor past what was written. The clone is taken at call time (before the
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// first await), matching the JSONL backend.
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assertSerializable(events)
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const batch = events.map(e => structuredClone(e))
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return this.serialize(id, () => this.appendCore(id, batch))
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}
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private async appendCore(id: SessionId, events: readonly SessionEvent[]): Promise<void> {
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/**
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* Durably append a batch in ONE transaction: materialize the sessions row (if
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* lazy) and INSERT every event, or roll back entirely. The transaction is the
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* atomicity + durability boundary, so a mid-batch failure (a UNIQUE violation
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* on a duplicated seq) leaves the stored log untouched.
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*/
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async appendBatch(meta: SessionHeader, events: readonly SessionEvent[], isMaterialized: boolean): Promise<void> {
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await this.ready
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if (events.length === 0) return
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let state = this.states.get(id)
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if (state === undefined) state = await this.adopt(id)
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// Contiguity contract: each event's seq must continue the stored log.
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for (const [i, event] of events.entries()) {
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if (event.seq !== state.cursor + i) {
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throw new Error(`append seq mismatch for "${id}": expected ${state.cursor + i} at index ${i}, got ${event.seq}`)
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}
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}
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// The transaction is the durability + atomicity boundary: materialize the
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// sessions row (if lazy) and INSERT every event, or roll back entirely. A
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// BEGIN/COMMIT around the batch means a mid-batch failure (a UNIQUE
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// violation on a duplicated seq from a concurrent writer) leaves the stored
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// log untouched, so the cursor stays truthful and a retry is clean. (A crash
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// tail is already gone: load() physically deletes the torn fragment and
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// durably closes the interrupted turn before returning, so by the time any
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// append runs the stored log is balanced and contiguous.)
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const insertEvent = this.db.prepare(
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'INSERT INTO events (session_id, seq, type, time, data) VALUES (?, ?, ?, ?, ?)',
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)
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this.db.exec('BEGIN')
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try {
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if (!state.materialized) this.writeRow(state.meta)
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if (!isMaterialized) this.writeRow(meta)
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for (const event of events) {
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insertEvent.run(id, event.seq, event.type, event.time, JSON.stringify(event.data))
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insertEvent.run(meta.id, event.seq, event.type, event.time, JSON.stringify(event.data))
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}
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this.db.exec('COMMIT')
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} catch (error) {
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this.db.exec('ROLLBACK')
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throw error
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}
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state.materialized = true
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state.cursor += events.length
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}
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load(id: SessionId): Promise<{ meta: SessionHeader; events: SessionEvent[] }> {
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return this.serialize(id, () => this.loadCore(id))
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}
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private async loadCore(id: SessionId): Promise<{ meta: SessionHeader; events: SessionEvent[] }> {
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/**
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* Make a crash repair durable in ONE transaction: DELETE the torn tail (from
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* `tornMarker`) and INSERT the synthetic `closers`. After COMMIT the stored rows
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* == the balanced log.
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*/
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async commitRepair(meta: SessionHeader, tornMarker: number | undefined, closers: readonly SessionEvent[]): Promise<void> {
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await this.ready
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const row = this.rowFor(id)
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if (row === undefined) throw new Error(`session "${id}" not found`)
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const meta = rowToMeta(row)
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this.assertVersion(meta)
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// Read every stored row ordered by seq, then scan for the preserved prefix:
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// the longest seq-contiguous, parseable run, INCLUDING the real events of an
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// interrupted final turn after the last turn/end (a turn can be huge — they
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// are never truncated). scanRows works off the seq+type COLUMNS for the
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// last-turn/end boundary, so a malformed `data` in a torn tail row is
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// discarded (not unloadable); only a parse error / seq gap in the COMMITTED
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// region (at or before the last turn/end) throws (genuine corruption).
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const eventRows = this.db
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.prepare('SELECT seq, type, time, data FROM events WHERE session_id = ? ORDER BY seq')
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.all(id) as unknown as EventRow[]
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const { preserved, tornFrom } = scanRows(eventRows)
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// Crash-recovery (mutating load, same as the JSONL backend): if the log ended
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// mid-turn, close it DURING load so disk, the returned log, and the cursor all
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// agree — both append routes then continue with no special-casing. Synthesize
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// the boundary events (a step/end if a step was open, then a
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// turn/end {kind:'interrupted'}); the interrupted turn's real events are
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// preserved, never truncated (the session-persistence RFC).
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const closers = interruptedTurnClosers(preserved)
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const balanced = [...preserved, ...closers]
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// Physically repair the stored log inside one transaction: DELETE the torn
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// tail fragment (if any), then INSERT the synthetic closers. After COMMIT the
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// stored rows == balanced, so the cursor is truthful and the next append
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// continues cleanly with no deferred repair. The metadata row stays as-is
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// even when preserved.length === 0 (an all-tail crash): the session WAS
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// materialized by the partial append, so has()/list() still report it — the
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// same as the JSONL backend, whose file likewise survives a first append that
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// never reached turn/end.
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if (tornFrom !== undefined || closers.length > 0) {
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this.db.exec('BEGIN')
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try {
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if (tornFrom !== undefined) {
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this.db.prepare('DELETE FROM events WHERE session_id = ? AND seq >= ?').run(id, tornFrom)
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}
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if (closers.length > 0) {
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const insertEvent = this.db.prepare('INSERT INTO events (session_id, seq, type, time, data) VALUES (?, ?, ?, ?, ?)')
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for (const event of closers) {
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insertEvent.run(id, event.seq, event.type, event.time, JSON.stringify(event.data))
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}
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}
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this.db.exec('COMMIT')
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} catch (error) {
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// The DELETE+INSERT cannot collide (a row at a closer's seq is preserved
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// or deleted as torn first); this rolls back a DB-level failure (disk
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// full, etc.), unreachable in test.
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/* v8 ignore start */
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this.db.exec('ROLLBACK')
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throw error
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/* v8 ignore stop */
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this.db.exec('BEGIN')
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try {
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if (tornMarker !== undefined) {
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this.db.prepare('DELETE FROM events WHERE session_id = ? AND seq >= ?').run(meta.id, tornMarker)
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}
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if (closers.length > 0) {
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const insertEvent = this.db.prepare('INSERT INTO events (session_id, seq, type, time, data) VALUES (?, ?, ?, ?, ?)')
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for (const event of closers) {
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insertEvent.run(meta.id, event.seq, event.type, event.time, JSON.stringify(event.data))
|
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}
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}
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this.db.exec('COMMIT')
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} catch (error) {
|
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// The DELETE+INSERT cannot collide (a row at a closer's seq is preserved or
|
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// deleted as torn first); this rolls back a DB-level failure (disk full,
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// etc.), unreachable in test.
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/* v8 ignore start */
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this.db.exec('ROLLBACK')
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throw error
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/* v8 ignore stop */
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}
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||||
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||||
// Record state at the balanced length. The state keeps its OWN copy of the
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// meta; the returned value is separate so a consumer mutating loaded.meta
|
||||
// cannot corrupt the backend's row metadata.
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this.states.set(id, {
|
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meta: { ...meta },
|
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cursor: balanced.length,
|
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materialized: true,
|
||||
})
|
||||
return { meta, events: balanced }
|
||||
}
|
||||
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||||
private async adoptLiveStoredPrefix(session: Session, seed: readonly SessionEvent[]): Promise<void> {
|
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/** Remove a session's row (ON DELETE CASCADE drops its events). */
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async deleteStored(id: SessionId): Promise<void> {
|
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await this.ready
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const row = this.rowFor(session.header.id)
|
||||
/* v8 ignore next -- caller checked row existence */
|
||||
if (row === undefined) throw new Error(`session "${session.header.id}" not found`)
|
||||
const meta = rowToMeta(row)
|
||||
this.assertVersion(meta)
|
||||
|
||||
const rows = this.db
|
||||
.prepare('SELECT seq, type, time, data FROM events WHERE session_id = ? ORDER BY seq')
|
||||
.all(session.header.id) as unknown as EventRow[]
|
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const { preserved, tornFrom } = scanRows(rows)
|
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if (!seedCoversPrefix(seed, preserved)) {
|
||||
throw new Error(`session "${session.header.id}" already has a persisted log that does not match this live session (id collision)`)
|
||||
}
|
||||
|
||||
if (tornFrom !== undefined) {
|
||||
this.db.prepare('DELETE FROM events WHERE session_id = ? AND seq >= ?').run(session.header.id, tornFrom)
|
||||
}
|
||||
this.states.set(session.header.id, {
|
||||
meta: { ...meta },
|
||||
cursor: preserved.length,
|
||||
materialized: true,
|
||||
owner: session,
|
||||
})
|
||||
const suffix = seed.slice(preserved.length)
|
||||
if (suffix.length > 0) await this.appendCore(session.header.id, suffix)
|
||||
this.db.prepare('DELETE FROM sessions WHERE id = ?').run(id)
|
||||
}
|
||||
|
||||
/** List all materialized sessions' metadata (every row is a materialized session). */
|
||||
async list(): Promise<SessionHeader[]> {
|
||||
await this.ready
|
||||
// Every metadata row is a materialized session: the row is written only by
|
||||
// the first append (a created-but-never-appended session has no row), so
|
||||
// listing all rows is exactly the materialized set.
|
||||
const rows = this.db
|
||||
.prepare('SELECT * FROM sessions')
|
||||
.all() as unknown as SessionRow[]
|
||||
return rows.map(rowToMeta)
|
||||
}
|
||||
|
||||
async has(id: SessionId): Promise<boolean> {
|
||||
/** Close the database handle (awaited by the coordinator's dispose, post-drain). */
|
||||
async close(): Promise<void> {
|
||||
await this.ready
|
||||
const state = this.states.get(id)
|
||||
if (state?.materialized) return true
|
||||
// A metadata row exists iff the session was materialized by a first append.
|
||||
return this.rowFor(id) !== undefined
|
||||
}
|
||||
|
||||
delete(id: SessionId): Promise<void> {
|
||||
return this.serialize(id, () => this.deleteCore(id))
|
||||
}
|
||||
|
||||
private async deleteCore(id: SessionId): Promise<void> {
|
||||
await this.ready
|
||||
// ON DELETE CASCADE drops the session's events with its row.
|
||||
this.db.prepare('DELETE FROM sessions WHERE id = ?').run(id)
|
||||
this.states.delete(id)
|
||||
this.db.close()
|
||||
}
|
||||
|
||||
// --- row helpers ---
|
||||
|
||||
/** Fetch a session's row, or undefined if absent. */
|
||||
private rowFor(id: SessionId): SessionRow | undefined {
|
||||
const row = this.db.prepare('SELECT * FROM sessions WHERE id = ?').get(id) as unknown as SessionRow | undefined
|
||||
return row
|
||||
return this.db.prepare('SELECT * FROM sessions WHERE id = ?').get(id) as unknown as SessionRow | undefined
|
||||
}
|
||||
|
||||
/**
|
||||
* Insert-or-replace a session's metadata row. The only caller is the first
|
||||
* materializing `append`, so writing the row IS the materialization (its
|
||||
* existence is the signal `has`/`list` read); a never-appended session has no
|
||||
* row at all.
|
||||
* materializing `appendBatch`, so writing the row IS the materialization (its
|
||||
* existence is the signal `has`/`list` read).
|
||||
*/
|
||||
private writeRow(meta: SessionHeader): void {
|
||||
this.db.prepare(`
|
||||
@@ -346,190 +253,6 @@ export class SessionPersistenceSqlite extends SessionPersistence {
|
||||
meta.parentSession ?? null,
|
||||
)
|
||||
}
|
||||
|
||||
/** Build a state for a session present in the DB but not yet in memory. */
|
||||
private async adopt(id: SessionId): Promise<SessionState> {
|
||||
await this.loadCore(id) // sets the state; load (serialized) would deadlock
|
||||
const state = this.states.get(id)
|
||||
/* v8 ignore next -- loadCore always sets the state for the id */
|
||||
if (!state) throw new Error(`failed to adopt session "${id}"`)
|
||||
return state
|
||||
}
|
||||
|
||||
private assertVersion(meta: SessionHeader): void {
|
||||
if (meta.version !== 1) {
|
||||
throw new Error(`unsupported session format version ${meta.version} for "${meta.id}" (only v1 is supported)`)
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* Run `op` after any in-flight operation for the same session id, so writes
|
||||
* for one session never interleave. Errors do not poison the chain. NOTE:
|
||||
* serialized public methods must NOT call each other (deadlock); they call
|
||||
* the unserialized `*Core` helpers instead.
|
||||
*/
|
||||
private serialize<T>(id: SessionId, op: () => Promise<T>): Promise<T> {
|
||||
const prior = this.chains.get(id) ?? Promise.resolve()
|
||||
const next = prior.then(op, op)
|
||||
this.chains.set(id, next.then(() => undefined, () => undefined))
|
||||
return next
|
||||
}
|
||||
|
||||
// --- write path (session/event → flush drain) ---
|
||||
|
||||
private installWritePath(): void {
|
||||
const ctx = this.ctx
|
||||
|
||||
ctx.on('session/created', (session) => { void this.initFor(session) })
|
||||
|
||||
// Snapshot + buffer every event (the live object is mutable; clone so a
|
||||
// later in-place mutation cannot rewrite a buffered event). Serializability
|
||||
// is guaranteed at the source (Session.append), so structuredClone is safe.
|
||||
ctx.on('session/event', (session, event) => {
|
||||
let buffer = this.buffers.get(session)
|
||||
if (!buffer) this.buffers.set(session, buffer = [])
|
||||
buffer.push(structuredClone(event))
|
||||
})
|
||||
|
||||
ctx.on('session/flush', session => this.flush(session))
|
||||
|
||||
// Dispose must reach quiescence: await every init + final drain, then close
|
||||
// the database, BEFORE returning, so no write lands after teardown.
|
||||
ctx.effect(() => async () => {
|
||||
let disposeError: unknown
|
||||
try {
|
||||
const errors = [
|
||||
...await settledErrors(this.inits.values()),
|
||||
...await settledErrors([...this.buffers.keys()].map(s => this.flush(s))),
|
||||
...await settledErrors(this.chains.values()),
|
||||
]
|
||||
if (errors.length > 0) {
|
||||
throw new AggregateError(errors, 'session-persistence-sqlite dispose failed')
|
||||
}
|
||||
} catch (error: unknown) {
|
||||
disposeError = error
|
||||
throw error
|
||||
} finally {
|
||||
try {
|
||||
await this.ready
|
||||
this.db.close()
|
||||
} catch (error: unknown) {
|
||||
/* v8 ignore next -- open/close failure racing disposal is a defensive teardown edge */
|
||||
if (disposeError === undefined) throw error
|
||||
// Opening/closing the database can only add teardown context here; keep
|
||||
// the already-captured init/flush/chain AggregateError as the primary
|
||||
// disposal failure instead of masking it from callers.
|
||||
}
|
||||
}
|
||||
}, 'session-persistence-sqlite write path')
|
||||
|
||||
// HMR: a hot reload does not replay session/created, so seed existing live
|
||||
// sessions (mirrors dsh-invariants and the JSONL backend).
|
||||
for (const session of ctx.sessions.list()) void this.initFor(session)
|
||||
}
|
||||
|
||||
/** Start (once) the async init for a session and remember its promise. */
|
||||
private initFor(session: Session): Promise<void> {
|
||||
const existing = this.inits.get(session)
|
||||
if (existing) return existing
|
||||
const seed = session.events.map(e => structuredClone(e))
|
||||
const p = this.onCreated(session, seed)
|
||||
p.catch(() => { /* observed by flush/dispose via the stored promise */ })
|
||||
this.inits.set(session, p)
|
||||
return p
|
||||
}
|
||||
|
||||
/**
|
||||
* On session/created: sync the backend's state to a live Session. Cases
|
||||
* mirror the JSONL backend:
|
||||
* 1. Already tracked → no-op (or claim ownerless state if the seed matches).
|
||||
* 2. A row EXISTS and is a seq-aligned PREFIX of the live events → adopt
|
||||
* (HMR/resume), persisting any live suffix beyond the stored prefix.
|
||||
* 3. A row EXISTS but is NOT a prefix → reject (id collision).
|
||||
* 4. No row → a genuinely new session: register meta (lazy) + persist seed.
|
||||
*/
|
||||
private async onCreated(session: Session, seed: readonly SessionEvent[]): Promise<void> {
|
||||
await this.ready
|
||||
const id = session.header.id
|
||||
const tracked = this.states.get(id)
|
||||
if (tracked !== undefined) {
|
||||
/* v8 ignore next -- initFor dedupes per session object; same-object re-entry can't occur */
|
||||
if (tracked.owner === session) return
|
||||
if (tracked.owner === undefined) {
|
||||
// Ownerless state from a public create()/load(). The first live session
|
||||
// claims it ONLY if its seed reproduces the persisted prefix.
|
||||
if (!await this.seedMatchesPersisted(id, seed, tracked.cursor)) {
|
||||
throw new Error(`session "${id}" is already persisted with ${tracked.cursor} event(s) that do not match this live session (id collision)`)
|
||||
}
|
||||
tracked.owner = session
|
||||
const suffix = seed.slice(tracked.cursor)
|
||||
if (suffix.length > 0) await this.append(id, suffix)
|
||||
return
|
||||
}
|
||||
// Owned by a DIFFERENT live session. Reclaim ONLY a truly-abandoned id
|
||||
// (never materialized, no pending buffer); else it is a real collision.
|
||||
const ownerBuffer = this.buffers.get(tracked.owner)
|
||||
if (!tracked.materialized && !ownerBuffer?.length) {
|
||||
this.states.delete(id)
|
||||
} else {
|
||||
throw new Error(`session "${id}" is already bound to a different live session in this backend (id collision)`)
|
||||
}
|
||||
}
|
||||
|
||||
const row = this.rowFor(id)
|
||||
if (row !== undefined) {
|
||||
// Adopt a LIVE prefix without crash-repairing an open turn as interrupted;
|
||||
// HMR may still append the real completion from the live Session.
|
||||
await this.serialize(id, () => this.adoptLiveStoredPrefix(session, seed))
|
||||
return
|
||||
}
|
||||
|
||||
// case 4: a genuinely new session.
|
||||
const meta: SessionHeader = { ...session.header }
|
||||
await this.create(meta)
|
||||
const created = this.states.get(id)
|
||||
/* v8 ignore next -- create() always sets the state for the id */
|
||||
if (created !== undefined) created.owner = session
|
||||
if (seed.length > 0) await this.append(id, seed)
|
||||
}
|
||||
|
||||
/** The preserved events for a session id (torn tail excluded, turn NOT yet closed). */
|
||||
private eventsFor(id: SessionId): SessionEvent[] {
|
||||
const rows = this.db
|
||||
.prepare('SELECT seq, type, time, data FROM events WHERE session_id = ? ORDER BY seq')
|
||||
.all(id) as unknown as EventRow[]
|
||||
// Scan on seq+type columns, parsing `data` only for the preserved prefix (a
|
||||
// malformed torn tail must not throw here — same as loadCore). Returns the
|
||||
// preserved events WITHOUT the synthetic closers, so a collision check
|
||||
// compares a live seed against the real on-disk events, mirroring the JSONL
|
||||
// backend's scanLog use in onCreated.
|
||||
return scanRows(rows).preserved
|
||||
}
|
||||
|
||||
/** Whether a live session's seed reproduces the first `cursor` stored events. */
|
||||
private async seedMatchesPersisted(id: SessionId, seed: readonly SessionEvent[], cursor: number): Promise<boolean> {
|
||||
await this.ready
|
||||
if (cursor === 0) return true
|
||||
return seedCoversPrefix(seed, this.eventsFor(id).slice(0, cursor))
|
||||
}
|
||||
|
||||
private async flush(session: Session): Promise<void> {
|
||||
await this.inits.get(session)
|
||||
await this.serialize(session.header.id, () => this.drain(session))
|
||||
}
|
||||
|
||||
/** Drain a session's write buffer to the database. Caller serializes per id. */
|
||||
private async drain(session: Session): Promise<void> {
|
||||
const buffer = this.buffers.get(session)
|
||||
if (!buffer?.length) return
|
||||
const batch = buffer.slice()
|
||||
const state = this.states.get(session.header.id)
|
||||
/* v8 ignore next -- state is always set by the awaited init before flush */
|
||||
const cursor = state?.cursor ?? 0
|
||||
const fresh = batch.filter(e => e.seq >= cursor)
|
||||
if (fresh.length > 0) await this.appendCore(session.header.id, fresh)
|
||||
buffer.splice(0, batch.length)
|
||||
}
|
||||
}
|
||||
|
||||
export default SessionPersistenceSqlite
|
||||
Reference in New Issue
Block a user