sync.ts

1import type { Database } from "bun:sqlite";2import {3	applyHidden,4	knownEventIds,5	knownObject,6	knownReleases,7	knownSave,8	land,9	mirrorState,10	openMirror,11	type StoredObject,12	storeObjects,13} from "../mirror/store.ts";14import type { BucketSource } from "../server/config.ts";15import {16	hiddenPaths,17	hiddenToHand,18	isRegistered,19	keepState,20	recordHiddenHanded,21	recordSync,22	registerRepo,23	renamedTo,24} from "../server/db.ts";25import { RESERVED_NAMES } from "../server/reserved.ts";26import { dropTarballs } from "../tarball/cache.ts";27import { type Bucket, inTurn, KEPR_PREFIX, openBucket } from "./reader.ts";28import {29	BucketError,30	checkFormat,31	type EventRecord,32	escapePath,33	isSafePath,34	listEventIds,35	listReleaseVersions,36	listRepos,37	OversizedObject,38	objectSize,39	type ReleaseRecord,40	readEvent,41	readHead,42	readObject,43	readRelease,44	readReleasesLatest,45	readSave,46	type SaveRecord,47} from "./repo.ts";4849const INTERVAL_MS = 2 * 60 * 1000;50// Compressed bytes a sync holds before landing them; sized for a 2 GB host.51const LANDING_BYTES = 32 * 1024 * 1024;52const LANDING_SAVES = 100;53// Bucket reads in flight at once. Each waits about 170 ms on Tylee's round trip to the bucket54// (measured 2026-10-02), so reading one at a time left the line idle.55const READS_AT_ONCE = 16;56// Compressed object bytes being read at once; a larger object waits and is read alone.57const READ_BYTES = 32 * 1024 * 1024;5859export type SyncTarget = {60	bucket: Bucket;61	kepr: Database;62	mirrorDir: string;63};6465let running: Promise<void> | null = null;6667/** Syncs every repo in the bucket; the admin console's "sync now" calls this too. Never overlaps itself. */68export function syncAll(target: SyncTarget): Promise<void> {69	return running ?? holdSync(() => syncEach(target));70}7172/**73 * Runs `work` once any sync under way has finished, and keeps syncs waiting until it is done: a74 * rename moves a repo's keys, which a sync must never see half moved.75 */76export function holdSync(work: () => Promise<void>): Promise<void> {77	// Cleared before anyone awaiting `work` resumes, so a sync asked for next starts afresh.78	const mine = (running ?? Promise.resolve()).then(work).finally(() => {79		if (running === slot) running = null;80	});81	const slot = mine.catch(() => {});82	running = slot;83	return mine;84}8586/**87 * What the app asks of the sync: one now, syncs held off while some work runs, a changed hidden88 * list applied, new bucket settings followed. Mirrors have one writer, the sync, so hidden lists go89 * through it too.90 */91export type Syncer = {92	syncAll(): Promise<void>;93	hold(work: () => Promise<void>): Promise<void>;94	applyHidden(repos: string[]): Promise<void>;95	setBucket(source: BucketSource): void;96};9798/** The sync in this thread, as the worker and the tests run it. */99export function localSyncer(target: SyncTarget): Syncer {100	return {101		syncAll: () => syncAll(target),102		hold: holdSync,103		applyHidden: async (repos) => {104			for (const asked of repos) {105				// A rename may have moved the repo while this waited on its hold.106				const repo = renamedTo(target.kepr, asked) ?? asked;107				if (!isRegistered(target.kepr, repo)) continue;108				applyHidden(openMirror(target.mirrorDir, repo), hiddenPaths(target.kepr, repo));109			}110		},111		setBucket: (source) => Object.assign(target.bucket, openBucket(source)),112	};113}114115/** A request to the sync's worker (`worker.ts`), and its reply. */116export type SyncRequest =117	| { kind: "start"; dataDir: string; source: BucketSource }118	| { kind: "sync" | "hold" | "release"; id: number }119	| { kind: "hidden"; id: number; repos: string[] }120	| { kind: "bucket"; source: BucketSource };121export type SyncReply = { kind: "done"; id: number; error?: string };122123/**124 * The sync on its own thread (2026-10-02), so a landing, a recount or a migration never stalls a125 * request. A worker that dies takes Kepr down with126 * it, for the service manager to restart, rather than leaving requests waiting on it.127 */128export function startSyncWorker(dataDir: string, source: BucketSource): Syncer {129	const worker = new Worker(new URL("./worker.ts", import.meta.url));130	// The server keeps Kepr running; the worker alone never should.131	worker.unref();132	const waiting = new Map<number, { resolve: () => void; reject: (error: Error) => void }>();133	let next = 0;134	worker.addEventListener("error", (event) => {135		console.error(`kepr: the sync worker failed: ${event.message}`);136		process.exit(1);137	});138	worker.addEventListener("message", ({ data }: MessageEvent<SyncReply>) => {139		const reply = waiting.get(data.id);140		waiting.delete(data.id);141		if (data.error === undefined) reply?.resolve();142		else reply?.reject(new Error(data.error));143	});144	const send = (request: SyncRequest) => worker.postMessage(request);145	const ask = (request: (id: number) => SyncRequest) =>146		new Promise<number>((resolve, reject) => {147			const id = next++;148			waiting.set(id, { resolve: () => resolve(id), reject });149			send(request(id));150		});151	send({ kind: "start", dataDir, source });152	return {153		syncAll: async () => {154			await ask((id) => ({ kind: "sync", id }));155		},156		async hold(work) {157			const id = await ask((id) => ({ kind: "hold", id }));158			try {159				await work();160			} finally {161				send({ kind: "release", id });162			}163		},164		applyHidden: async (repos) => {165			await ask((id) => ({ kind: "hidden", id, repos }));166		},167		setBucket: (source) => send({ kind: "bucket", source }),168	};169}170171export function startSyncLoop(target: SyncTarget): void {172	const tick = () => syncAll(target).catch((error) => console.error(`kepr: sync failed: ${error}`));173	tick();174	setInterval(tick, INTERVAL_MS);175}176177async function syncEach(target: SyncTarget): Promise<void> {178	let repos: string[];179	try {180		repos = await listRepos(target.bucket);181	} catch (error) {182		keepState(target.kepr, "bucket_error", String(error));183		throw error;184	}185	// What the console's status shows, so it never asks the bucket itself.186	keepState(target.kepr, "bucket_error", null);187	keepState(target.kepr, "bucket_read_at", String(Math.floor(Date.now() / 1000)));188	keepState(target.kepr, "bucket_repos", JSON.stringify(repos));189	for (const repo of repos) {190		registerRepo(target.kepr, repo);191		let error: string | null = null;192		if (RESERVED_NAMES.has(repo)) {193			error = `not synced: the name "${repo}" clashes with Kepr's own /${repo} route; rename the repo`;194		} else {195			try {196				const mirror = openMirror(target.mirrorDir, repo);197				const events = await syncRepo(target.bucket, mirror, repo, hiddenPaths(target.kepr, repo));198				if (events.some((event) => event.kind === "strip")) await dropTarballs(target.bucket, repo);199			} catch (cause) {200				error = cause instanceof Error ? cause.message : String(cause);201			}202		}203		recordSync(target.kepr, repo, Math.floor(Date.now() / 1000), error);204		await handHidden(target, repo);205	}206}207208/**209 * Hands a repo's hidden paths to Koh at `.kepr/hidden/<repo>`, one per line, for it to add to210 * `.kohignore`, unless they are known to be there already, then drops the tarballs kept under the211 * old list. The sync does it rather than the console, so a failed write or a restart is retried at212 * the next pass, and it never overlaps a rename.213 */214async function handHidden(target: SyncTarget, repo: string): Promise<void> {215	const list = hiddenToHand(target.kepr, repo);216	if (list === null) return;217	const paths = list.split("\n").filter(Boolean);218	const bytes = new TextEncoder().encode(paths.map((path) => `${path}\n`).join(""));219	// Unknown until the write is confirmed, so a restart or failure mid-write is written again220	// even if the list changes back to the one recorded before.221	recordHiddenHanded(target.kepr, repo, null);222	try {223		await target.bucket.put(`${KEPR_PREFIX}hidden/${repo}`, bytes, "text/plain");224	} catch (error) {225		console.error(`kepr: handing ${repo}'s hidden paths to Koh failed: ${error}`);226		return;227	}228	recordHiddenHanded(target.kepr, repo, list);229	// Only storage: a kept tarball is never served once its generation's hidden list has changed.230	await dropTarballs(target.bucket, repo).catch((error) =>231		console.error(`kepr: dropping ${repo}'s kept tarballs failed: ${error}`),232	);233}234235/**236 * Koh's steal flow (§9.4) against a mirror: walk back from the remote head to a save the mirror has,237 * fetch what is missing, and land it, in batches oldest first. Events are listed every time, since a238 * flag or a strip arrives without moving `head`; releases only when `head` or `releases/latest`239 * moved (§18), since publishing one moves both. A path §5.5 refuses, or one whose object inflates240 * past Koh's file limit, is quarantined: the save lands without it, as if stripped. `hidden` is241 * applied first, so a list changed since the last sync takes effect even with nothing new. Returns242 * the events it landed.243 */244export async function syncRepo(245	bucket: Bucket,246	mirror: Database,247	repo: string,248	hidden: string[] = [],249	landingBytes = LANDING_BYTES,250	readBytes = READ_BYTES,251): Promise<EventRecord[]> {252	applyHidden(mirror, hidden);253	await checkFormat(bucket, repo);254	const head = await readHead(bucket, repo);255	if (head === null) return [];256	const unknown = new Set<string>();257	for (let cursor = head; cursor !== "" && !knownSave(mirror, cursor); ) {258		if (unknown.has(cursor)) throw new BucketError(`${repo}: save ${cursor} is its own ancestor`);259		unknown.add(cursor);260		cursor = (await readSave(bucket, repo, cursor)).parent;261	}262	// Oldest first, landing whenever the batch passes `landingBytes` of objects or LANDING_SAVES263	// records: a first sync of a big repo never holds its whole history in memory, and one cut short264	// resumes from the last batch. Records are read again here rather than kept from the walk, since265	// each lists every file of its tree.266	let saves: SaveRecord[] = [];267	let objects = new Map<string, StoredObject>();268	let quarantined: string[] = [];269	let fetched = 0;270	const oversized = new Set<string>();271	const landBatch = (batchHead: string) => {272		land(mirror, {273			head: batchHead,274			releasesLatest: mirrorState(mirror, "releases_latest") ?? "",275			saves,276			objects,277			events: [],278			releases: [],279			quarantined,280		});281		saves = [];282		objects = new Map();283		quarantined = [];284		fetched = 0;285	};286	const gate = byteGate(readBytes);287	let failure: unknown = null;288	// Reads one object into `ahead`. A read the gate admits after the batch filled, or after another289	// read failed, puts its hash back for the next batch instead.290	const readInto = async (ahead: Map<string, StoredObject>, wanted: string[], hash: string) => {291		const size = await objectSize(bucket, repo, hash);292		await gate.enter(size);293		try {294			if (failure !== null || fetched >= landingBytes) {295				wanted.unshift(hash);296				return;297			}298			const object = await readObject(bucket, repo, hash);299			ahead.set(hash, object);300			fetched += object.compressed.length;301		} catch (cause) {302			if (!(cause instanceof OversizedObject)) throw cause;303			oversized.add(hash);304		} finally {305			gate.leave(size);306		}307	};308	const ids = [...unknown].reverse();309	for (let start = 0; start < ids.length; start += READS_AT_ONCE) {310		const records = await inTurn(ids.slice(start, start + READS_AT_ONCE), READS_AT_ONCE, (id) =>311			readSave(bucket, repo, id),312		);313		for (const save of records) {314			quarantined.push(...save.quarantined);315			// One save can hold more than a batch, as a first import does: its objects are stored316			// ahead of it, after the saves before it have landed, so no landing's cleanup sees them317			// unreferenced.318			const ahead = new Map<string, StoredObject>();319			const wanted = [...new Set(save.files.map((file) => file.hash))].filter(320				(hash) => !objects.has(hash) && !oversized.has(hash) && !knownObject(mirror, hash),321			);322			while (wanted.length > 0) {323				// No read starts once the batch is full, so a batch passes `landingBytes` by at most324				// the reads under way, which the gate holds to `readBytes` or one larger object.325				const reader = async () => {326					while (failure === null && fetched < landingBytes && wanted.length > 0) {327						await readInto(ahead, wanted, wanted.shift() as string).catch((cause) => {328							failure ??= cause;329						});330					}331				};332				// Every reader settles before a failure is reported, so none outlives this sync.333				await Promise.all(Array.from({ length: READS_AT_ONCE }, reader));334				if (failure !== null) throw failure;335				if (fetched >= landingBytes) {336					const last = saves.at(-1);337					if (last) landBatch(last.id);338					storeObjects(mirror, ahead);339					ahead.clear();340					fetched = 0;341				}342			}343			for (const [hash, object] of ahead) objects.set(hash, object);344			quarantined.push(345				...save.files.filter((f) => oversized.has(f.hash)).map((f) => escapePath(f.path)),346			);347			save.files = save.files.filter((file) => !oversized.has(file.hash));348			saves.push(save);349			if (saves.length >= LANDING_SAVES && save.id !== head) landBatch(save.id);350		}351	}352	const known = knownEventIds(mirror);353	const newEvents = (await listEventIds(bucket, repo)).filter((id) => !known.has(id));354	const events = (355		await inTurn(newEvents, READS_AT_ONCE, (id) => readEvent(bucket, repo, id))356	).filter(357		// Koh ignores it too: no save can hold an illegal path (§5.5).358		(event) => event.kind !== "strip" || isSafePath(event.path),359	);360	const releasesLatest = (await readReleasesLatest(bucket, repo)) ?? "";361	const moved =362		mirrorState(mirror, "head") !== head ||363		mirrorState(mirror, "releases_latest") !== releasesLatest;364	const releases = moved ? await newReleases(bucket, mirror, repo) : [];365	if (!moved && events.length === 0) return [];366	land(mirror, {367		head,368		releasesLatest,369		saves,370		objects,371		events,372		releases,373		quarantined,374	});375	return events;376}377378/** Admits reads while their bytes in flight stay within `limit`; a larger one waits to go alone. */379function byteGate(limit: number) {380	let inFlight = 0;381	let waiting: (() => void)[] = [];382	return {383		async enter(size: number): Promise<void> {384			while (inFlight > 0 && inFlight + size > limit) {385				await new Promise<void>((resolve) => waiting.push(resolve));386			}387			inFlight += size;388		},389		leave(size: number): void {390			inFlight -= size;391			const woken = waiting;392			waiting = [];393			for (const wake of woken) wake();394		},395	};396}397398async function newReleases(399	bucket: Bucket,400	mirror: Database,401	repo: string,402): Promise<ReleaseRecord[]> {403	const known = knownReleases(mirror);404	const versions = (await listReleaseVersions(bucket, repo)).filter((v) => !known.has(v));405	return inTurn(versions, READS_AT_ONCE, (version) => readRelease(bucket, repo, version));406}