usenet-indexer/app/services/leases.ts

import db from '@adonisjs/lucid/services/db'
import coordinatorConfig from '#config/coordinator'
import RuleSets from '#services/rule_sets'
import Spool from '#services/spool'
import type { Lease } from '#lib/edge/index'

export class LeaseLost extends Error {}

/**
 * Ranges for workers (REBUILD.md, coordinator): the next range with chunks
 * spooled, by priority (oldest era first), else the next planned one (the
 * prefetcher fetches leased ranges first; the worker's stream waits). A
 * worker never waits for prefetching to choose its range: refused leases
 * left workers idle for 30 s, so fewer ranges were leased and fewer
 * prefetched (LOG.md 2026-10-09). A lease whose worker went quiet for
 * LEASE_TTL_SECONDS is taken over and resumes at its resume point.
 */
class Leases {
  async lease(nodeId: number): Promise<Lease | null> {
    const rules = await RuleSets.current()
    const take = (spooled: boolean) =>
      db.rawQuery(
        `UPDATE ranges r SET status = 'leased', node_id = ?, leased_at = now(), heartbeat_at = now(), attempts = attempts + 1, rule_version = ?
         WHERE r.id = (
           SELECT id FROM ranges
           WHERE ${spooled ? 'spooled_chunks > 0' : 'true'} AND next_id <= end_id
             AND (status = 'planned' OR (status = 'leased' AND heartbeat_at < now() - make_interval(secs => ?)))
           ORDER BY priority, id LIMIT 1 FOR UPDATE SKIP LOCKED)
         RETURNING r.id, r.group_id, r.start_id, r.end_id, r.next_id`,
        [nodeId, rules.version, coordinatorConfig.leaseTtlSeconds]
      )
    let { rows } = await take(true)
    if (rows.length === 0) ({ rows } = await take(false))
    const row = rows[0]
    if (!row) return null
    await db.from('nodes').where('id', nodeId).update({ last_seen_at: new Date() })
    const group = await db.from('groups').where('id', row.group_id).select('name').firstOrFail()
    return { range: { id: Number(row.id), group: group.name, start: Number(row.start_id), end: Number(row.end_id), next: Number(row.next_id) }, rules }
  }

  async leased(rangeId: number, nodeId: number) {
    const range = await db.from('ranges').where('id', rangeId).first()
    if (!range || range.status !== 'leased' || Number(range.node_id) !== nodeId) throw new LeaseLost(`Range ${rangeId} is not leased to this node`)
    return range
  }

  async heartbeat(rangeId: number, nodeId: number) {
    await this.leased(rangeId, nodeId)
    await db.from('ranges').where('id', rangeId).update({ heartbeat_at: new Date() })
    await db.from('nodes').where('id', nodeId).update({ last_seen_at: new Date() })
  }

  /** The worker reached the range's end: done, and its spooled chunks go. */
  async finish(rangeId: number, nodeId: number) {
    const range = await this.leased(rangeId, nodeId)
    if (Number(range.next_id) <= Number(range.end_id)) throw new LeaseLost(`Range ${rangeId} is at ${range.next_id}, not past its end ${range.end_id}`)
    await db.from('ranges').where('id', rangeId).update({ status: 'done', done_at: new Date(), heartbeat_at: new Date() })
    await Spool.remove(rangeId)
  }

  /**
   * A worker got a chunk that doesn't inflate: the spooled chunk goes and
   * the range back to the queue (the prefetcher fetches leased ranges'
   * missing chunks again; the next worker resumes at the range's resume point).
   */
  async corrupt(rangeId: number, nodeId: number, from: number) {
    const range = await this.leased(rangeId, nodeId)
    const span = Spool.chunksOf({ start: Number(range.start_id), end: Number(range.end_id) }).find((s) => s.from === from)
    if (span) await Spool.removeChunk(rangeId, span)
    const plain: number[] = (range.plain_chunks ?? []).map(Number)
    if (plain.includes(from)) {
      // Fetched plain (deflated here) and still not inflating: not the server's compression; set aside.
      await db.from('ranges').where('id', rangeId).update({ status: 'failed', node_id: null, error: `chunk ${from} doesn't inflate, also fetched plain` })
      return
    }
    // The server's compressed reply is cut short (the same bytes every time): fetched plain next time.
    await db.rawQuery(`UPDATE ranges SET status = 'planned', node_id = NULL, plain_chunks = array_append(plain_chunks, ?::bigint) WHERE id = ?`, [from, rangeId])
  }

  /** A stopping worker gives its range back; the next one resumes it. */
  async release(rangeId: number, nodeId: number) {
    await this.leased(rangeId, nodeId)
    await db.from('ranges').where('id', rangeId).update({ status: 'planned', node_id: null })
  }
}

export default new Leases()