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a tool for shared writing and social publishing
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12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273747576777879import Client from "ioredis";import Redlock from "redlock";
// Publishing reads "does this draft already have a document?" and then writes// one, so two overlapping publishes of the same draft each mint a fresh rkey// and one of the resulting posts is left unlinked from the draft. Publishes// are serialized per leaflet: an in-process set catches overlap within one// server instance and, in production, a Redis lock catches overlap across// instances. A busy caller is refused rather than queued — a queued duplicate// would run as an "update" and hand its caller a second success (and a second// Bluesky post).const LOCK_TTL_MS = 5 * 60_000;const inFlight = new Set<string>();
const globalForPublishLock = globalThis as unknown as { __publishRedlock?: Redlock | null;};
function getRedlock(): Redlock | null { if (globalForPublishLock.__publishRedlock === undefined) { globalForPublishLock.__publishRedlock = process.env.NODE_ENV === "production" && process.env.REDIS_URL ? new Redlock([new Client(process.env.REDIS_URL)], { retryCount: 0 }) : null; } return globalForPublishLock.__publishRedlock;}
// Redlock reports a failed acquire as an ExecutionError whose per-attempt// votes carry the reason; only a ResourceLockedError vote means someone else// holds the lock (anything else is Redis being unreachable, which should// surface). The classes aren't reachable through the repo's redlock type shim,// so they're matched by name.type ExecutionStats = { votesAgainst: Map<unknown, Error> };async function isHeldElsewhere(error: unknown): Promise<boolean> { if (!(error instanceof Error) || error.name !== "ExecutionError") return false; let attempts = ( error as { attempts?: ReadonlyArray<Promise<ExecutionStats>> } ).attempts; let stats = await Promise.all(attempts ?? []); return stats.some((attempt) => [...attempt.votesAgainst.values()].some( (vote) => vote.name === "ResourceLockedError", ), );}
export type PublishLockResult<T> = | { acquired: true; value: T } | { acquired: false };
export async function withPublishLock<T>( leaflet_id: string, fn: () => Promise<T>,): Promise<PublishLockResult<T>> { if (inFlight.has(leaflet_id)) return { acquired: false }; inFlight.add(leaflet_id); try { let redlock = getRedlock(); let lock = null; if (redlock) { try { lock = await redlock.acquire([`publish:${leaflet_id}`], LOCK_TTL_MS); } catch (error) { if (await isHeldElsewhere(error)) return { acquired: false }; throw error; } } try { return { acquired: true, value: await fn() }; } finally { if (lock) await lock.release().catch(console.error); } } finally { inFlight.delete(leaflet_id); }}