Seed relay: nodes get their headers through the seed API

The seed API keeps a pool of NNTP connections (SEED_NNTP_CONNECTIONS) and
serves GET /api/v1/seed/ranges/:id/chunk?from=&to= for leased ranges:
the gzip stream the news server sent, passed on unopened. seed:node fetches
that way by default (SEED_FETCH=relay), so a node needs only a token and
SEED_CONNECTIONS; SEED_FETCH=direct keeps its own NNTP connections. All
fetching then comes from the indexer's IP (the account allows two).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/controllers/seed_controller.ts

@@ -1,5 +1,6 @@
 import type { HttpContext } from '@adonisjs/core/http'
 import SeedOrchestrator, { LeaseLost } from '#services/SeedOrchestrator'
+import SeedFetchPool from '#services/SeedFetchPool'
 import type { SeedBatch } from '#lib/seed/wire'
 
 /**
@@ -31,6 +32,27 @@ export default class SeedController {
     })
   }
 
+  /**
+   * GET /api/v1/seed/ranges/:id/chunk?from=&to= → the overviews of those
+   * articles as a zlib/gzip stream (relay nodes fetch through the indexer).
+   */
+  async chunk({ seedNode, params, request, response }: HttpContext) {
+    if (SeedFetchPool.size === 0) return response.serviceUnavailable({ error: 'Relay is off (SEED_NNTP_CONNECTIONS=0); fetch directly' })
+    const from = Number(request.input('from'))
+    const to = Number(request.input('to'))
+    if (!Number.isSafeInteger(from) || !Number.isSafeInteger(to)) return response.badRequest({ error: 'Expected ?from=&to=' })
+    return this.leased(response, async () => {
+      try {
+        const raw = await SeedOrchestrator.chunk(seedNode.id, Number(params.id), from, to)
+        response.header('content-type', 'application/octet-stream')
+        return response.send(raw)
+      } catch (error) {
+        if (error instanceof RangeError) return response.badRequest({ error: error.message })
+        throw error
+      }
+    })
+  }
+
   /** POST /api/v1/seed/ranges/:id/done */
   async done({ seedNode, params, response }: HttpContext) {
     return this.leased(response, async () => {

app/services/SeedFetchPool.ts

@@ -0,0 +1,91 @@
+import nntpConfig from '#config/nntp'
+import indexerConfig from '#config/indexer'
+import { XoverClient } from '#lib/nntp/xover_client'
+
+interface Slot {
+  client: XoverClient
+  group?: string
+  usedAt: number
+}
+
+/** A pooled connection unused this long is replaced: the news server may have dropped it. */
+const IDLE_MS = 2 * 60 * 1000
+
+/**
+ * NNTP connections in the seed API for relay nodes (CONCEPT.md D38): the
+ * indexer fetches overview chunks and passes the gzip stream on unopened, so
+ * nodes need no news server account and every connection comes from this
+ * machine's IP. SEED_NNTP_CONNECTIONS (0: relay off).
+ */
+class SeedFetchPool {
+  private idle: Slot[] = []
+  private open = 0
+  private waiters: (() => void)[] = []
+
+  get size() {
+    return indexerConfig.seed.nntpConnections
+  }
+
+  async fetch(group: string, from: number, to: number): Promise<Buffer> {
+    const slot = await this.acquire()
+    let ok = false
+    try {
+      if (slot.group !== group) {
+        await slot.client.group(group)
+        slot.group = group
+      }
+      const raw = await slot.client.xoverRaw(from, to)
+      ok = true
+      return raw
+    } finally {
+      this.release(slot, ok)
+    }
+  }
+
+  private async acquire(): Promise<Slot> {
+    while (true) {
+      const slot = this.idle.pop()
+      if (slot) {
+        if (Date.now() - slot.usedAt < IDLE_MS) return slot
+        slot.client.close()
+        this.open--
+        continue
+      }
+      if (this.open < this.size) {
+        this.open++
+        try {
+          const client = await XoverClient.connect({
+            host: nntpConfig.host,
+            port: nntpConfig.port,
+            secure: nntpConfig.secure,
+            servername: nntpConfig.tlsServername,
+            user: nntpConfig.user,
+            password: nntpConfig.password?.release(),
+            timeoutMs: nntpConfig.commandTimeoutMs,
+            compress: true,
+          })
+          return { client, usedAt: Date.now() }
+        } catch (error) {
+          this.open--
+          this.waiters.shift()?.()
+          throw error
+        }
+      }
+      await new Promise<void>((resolve) => this.waiters.push(resolve))
+    }
+  }
+
+  private release(slot: Slot, ok: boolean) {
+    if (ok) {
+      slot.usedAt = Date.now()
+      this.idle.push(slot)
+    } else {
+      // A failed command can leave the connection mid-reply: start afresh.
+      slot.client.close()
+      this.open--
+    }
+    this.waiters.shift()?.()
+  }
+}
+
+export default new SeedFetchPool()

app/services/SeedOrchestrator.ts

@@ -3,6 +3,7 @@ import db from '@adonisjs/lucid/services/db'
 import NntpService from '#services/NntpService'
 import SeedService from '#services/SeedService'
 import BackfillService from '#services/BackfillService'
+import SeedFetchPool from '#services/SeedFetchPool'
 import { articleAtDate } from '#lib/nntp/date_search'
 import { normalizeSeedFile, type SeedBatch } from '#lib/seed/wire'
 
@@ -92,6 +93,19 @@ class SeedOrchestrator {
     return stored
   }
 
+  /**
+   * Relay: overviews of `from`..`to` of a leased range, fetched here and handed
+   * on as the gzip stream the news server sent. Keeps the lease alive.
+   */
+  async chunk(nodeId: number, rangeId: number, from: number, to: number): Promise<Buffer> {
+    const range = await this.leased(nodeId, rangeId)
+    const start = Math.max(from, Number(range.start_id))
+    const end = Math.min(to, Number(range.end_id), start + 49_999)
+    if (end < start) throw new RangeError(`Articles ${from}–${to} are outside range ${rangeId}`)
+    await db.from('seed_ranges').where('id', rangeId).update({ heartbeat_at: new Date() })
+    return SeedFetchPool.fetch(range.group_name, start, end)
+  }
+
   async finish(nodeId: number, rangeId: number) {
     await this.leased(nodeId, rangeId)
     await db.from('seed_ranges').where('id', rangeId).update({ status: 'done', done_at: new Date(), heartbeat_at: new Date(), error: null })

commands/SeedNode.ts

@@ -1,11 +1,11 @@
-import { gzipSync } from 'node:zlib'
+import { gzipSync, unzipSync } from 'node:zlib'
 import { setTimeout as sleep } from 'node:timers/promises'
 import { BaseCommand, flags } from '@adonisjs/core/ace'
 import { CommandOptions } from '@adonisjs/core/types/ace'
 import nntpConfig from '#config/nntp'
 import indexerConfig from '#config/indexer'
-import { XoverClient } from '#lib/nntp/xover_client'
-import { runRange } from '#lib/seed/runner'
+import { XoverClient, parseOverviews, type Overview } from '#lib/nntp/xover_client'
+import { runRange, type OverviewSource } from '#lib/seed/runner'
 import type { SeedBatch } from '#lib/seed/wire'
 import type { OverviewHeader } from '#lib/ingest/segment'
 
@@ -56,6 +56,13 @@ export default class SeedNode extends BaseCommand {
   @flags.number({ description: 'XOVER chunks per batch posted to the API', default: 5 })
   declare submitEvery: number
 
+  @flags.string({
+    description:
+      'relay: headers come through the seed API (no NNTP account needed); direct: own NNTP connections (default: SEED_FETCH or relay)',
+    default: process.env.SEED_FETCH || 'relay',
+  })
+  declare fetch: string
+
   @flags.boolean({ description: 'Stop when there is nothing to lease instead of waiting' })
   declare once: boolean
 
@@ -77,7 +84,9 @@ export default class SeedNode extends BaseCommand {
     process.on('SIGINT', stop)
 
     const api = new SeedApi(base, token, (message) => this.logger.warning(message))
-    this.logger.info(`Seeding node for ${base} with ${this.connections} connection(s).`)
+    this.logger.info(
+      `Seeding node for ${base}: ${this.connections} range(s) at once, ${this.fetch === 'direct' ? 'own NNTP connections' : 'headers through the seed API'}.`
+    )
     await Promise.all(Array.from({ length: this.connections }, (_, i) => this.work(api, i + 1)))
     this.logger.info('Seeding node stopped.')
   }
@@ -97,6 +106,10 @@ export default class SeedNode extends BaseCommand {
           await this.pause(60_000)
           continue
         }
+        if (this.fetch !== 'direct') {
+          await this.workRange(api, new RelaySource(api, lease.id), lease, log)
+          continue
+        }
         if (!client) {
           try {
             client = await this.connect()
@@ -151,7 +164,7 @@ export default class SeedNode extends BaseCommand {
   /** Works one leased range; false when the NNTP connection should be replaced. */
   private async workRange(
     api: SeedApi,
-    client: XoverClient,
+    client: OverviewSource,
     lease: Lease,
     log: (message: string) => void
   ): Promise<boolean> {
@@ -230,38 +243,66 @@ class SeedApi {
 
   async post(path: string, body?: unknown): Promise<unknown> {
     const payload = body === undefined ? undefined : gzipSync(JSON.stringify(body))
+    const result = await this.request('POST', path, payload)
+    if (result === null) return null
+    const text = result.toString('utf8')
+    return text ? JSON.parse(text) : null
+  }
+
+  /** A binary GET (a relay chunk). */
+  async get(path: string): Promise<Buffer> {
+    return (await this.request('GET', path)) ?? Buffer.alloc(0)
+  }
+
+  private async request(method: string, path: string, payload?: Buffer): Promise<Buffer | null> {
     for (let attempt = 1; ; attempt++) {
       let status = 0
-      let text = ''
+      let data = Buffer.alloc(0)
       try {
         const response = await fetch(this.base + path, {
-          method: 'POST',
+          method,
           headers: {
             authorization: `Bearer ${this.token}`,
-            accept: 'application/json',
             ...(payload ? { 'content-type': 'application/json', 'content-encoding': 'gzip' } : {}),
           },
           body: payload,
           signal: AbortSignal.timeout(10 * 60 * 1000),
         })
         status = response.status
-        text = await response.text()
+        data = Buffer.from(await response.arrayBuffer())
       } catch (error: any) {
-        text = error.message
+        data = Buffer.from(error.message)
       }
+      const text = () => data.toString('utf8').slice(0, 300)
       if (status === 204) return null
-      if (status >= 200 && status < 300) return text ? JSON.parse(text) : null
+      if (status >= 200 && status < 300) return data
       if (status === 401) throw new Unauthorized('The seed API rejected this node token')
-      if (status === 409) throw new LeaseLost(text)
+      if (status === 409) throw new LeaseLost(text())
       // 404 comes from the proxy while the seed API restarts (a deploy): this API has no 404s of its own.
       if (status >= 400 && status < 500 && status !== 404)
-        throw new Error(`Seed API ${path}: ${status} ${text.slice(0, 300)}`)
+        throw new Error(`Seed API ${path}: ${status} ${text()}`)
       // Network errors, 404 and 5xx: storing a batch twice is harmless, so try again.
-      if (attempt >= 8)
-        throw new Error(`Seed API ${path}: ${status || 'no response'} ${text.slice(0, 300)}`)
+      if (attempt >= 8) throw new Error(`Seed API ${path}: ${status || 'no response'} ${text()}`)
       const wait = Math.min(120_000, 2000 * 2 ** (attempt - 1))
-      this.warn(`Seed API ${path}: ${status || text}; retrying in ${wait / 1000} s`)
+      this.warn(`Seed API ${path}: ${status || text()}; retrying in ${wait / 1000} s`)
       await sleep(wait)
     }
   }
 }
+
+/** A range's overviews through the seed API's relay (CONCEPT.md D38): no news server account on the node. */
+class RelaySource implements OverviewSource {
+  constructor(
+    private api: SeedApi,
+    private rangeId: number
+  ) {}
+
+  async group() {}
+
+  async xover(from: number, to: number): Promise<Overview[]> {
+    const raw = await this.api.get(
+      `/api/v1/seed/ranges/${this.rangeId}/chunk?from=${from}&to=${to}`
+    )
+    return raw.length > 0 ? parseOverviews(unzipSync(raw).toString('utf8')) : []
+  }
+}

config/indexer.ts

@@ -63,6 +63,11 @@ export default {
    * Header backfill (`group:backfill`, CONCEPT.md D32): low-priority,
    * header-only fetch ranges walking back through a group's history.
    */
+  seed: {
+    /** NNTP connections the seed API fetches with for relay nodes (CONCEPT.md D38); 0: relay off. */
+    nntpConnections: env.get('SEED_NNTP_CONNECTIONS', 0),
+  },
+
   backfill: {
     /** Backfill ranges waiting or running at a time, over all groups. */
     maxQueued: env.get('BACKFILL_MAX_QUEUED', 40),

lib/nntp/xover_client.ts

@@ -1,6 +1,6 @@
 import net from 'node:net'
 import tls from 'node:tls'
-import { unzipSync } from 'node:zlib'
+import { deflateSync, unzipSync } from 'node:zlib'
 
 export interface XoverClientOptions {
   host: string
@@ -90,6 +90,20 @@ export class XoverClient {
     return this.timed(() => this.overviews(from, to))
   }
 
+  /**
+   * Overviews of `from`..`to` as one zlib/gzip stream, as the server sent it when it
+   * compresses (plain replies are deflated here): the seed API passes these to nodes
+   * without unpacking them (CONCEPT.md D38). `parseOverviews(unzipSync(raw).toString())`.
+   */
+  async xoverRaw(from: number, to: number): Promise<Buffer> {
+    return this.timed(async () => {
+      const reply = await this.command(`XOVER ${from}-${to}`)
+      if (reply.startsWith('420') || reply.startsWith('423')) return deflateSync(Buffer.alloc(0))
+      await this.expect(reply, ['224'])
+      return reply.includes('COMPRESS=GZIP') ? (await this.compressedRaw()).raw : deflateSync(Buffer.from(await this.plainBody()))
+    })
+  }
+
   /** A reply that stalls for timeoutMs fails the connection; idle time between commands doesn't count. */
   private async timed<T>(exchange: () => Promise<T>): Promise<T> {
     this.sock.setTimeout(this.timeoutMs)
@@ -179,15 +193,20 @@ export class XoverClient {
     }
   }
 
-  /** A zlib/gzip stream followed by a "." line: complete once it ends in ".\r\n" and inflates. */
   private async compressedBody(): Promise<string> {
+    return (await this.compressedRaw()).text
+  }
+
+  /** A zlib/gzip stream followed by a "." line: complete once it ends in ".\r\n" and inflates. */
+  private async compressedRaw(): Promise<{ raw: Buffer; text: string }> {
     while (true) {
       const all = this.buffer()
       if (all.length > DOT_LINE.length && all.subarray(all.length - DOT_LINE.length).equals(DOT_LINE)) {
+        const raw = all.subarray(0, all.length - DOT_LINE.length)
         try {
-          const text = unzipSync(all.subarray(0, all.length - DOT_LINE.length)).toString('utf8')
+          const text = unzipSync(raw).toString('utf8')
           this.take(all.length)
-          return text
+          return { raw: Buffer.from(raw), text }
         } catch {
           // ".\r\n" inside the compressed data: wait for more.
         }

lib/seed/runner.ts

@@ -1,10 +1,16 @@
-import type { XoverClient, Overview } from '../nntp/xover_client.js'
+import type { Overview } from '../nntp/xover_client.js'
 import { segmentFromHeader, type IngestSegment, type OverviewHeader } from '../ingest/segment.js'
 import { FileAggregator } from '../aggregate/index.js'
 import { toFragment, toSeedFile, type SeedBatch } from './wire.js'
 
+/** Where a range's overviews come from: an NNTP connection, or the seed API's relay. */
+export interface OverviewSource {
+  group(name: string): Promise<unknown>
+  xover(from: number, to: number): Promise<Overview[]>
+}
+
 export interface RunRangeOptions {
-  client: XoverClient
+  client: OverviewSource
   group: string
   /** Inclusive article numbers. */
   start: number

seed-node/README.md

@@ -1,10 +1,18 @@
 # Seeding node
 
 A seeding node indexes old article ranges for the indexer (CONCEPT.md D37,
-D38). It asks the seed API for a range over HTTPS, fetches that range's
-headers over its own NNTP connections, groups them into files, and posts the
+D38). It asks the seed API for a range over HTTPS, gets that range's headers
+(by default through the seed API, which fetches them from the news server and
+passes them on gzip-compressed), groups them into files, and posts the
 results back. It only makes outgoing connections: no port forwarding,
-database or Redis.
+database, Redis or news server account. Only a token and
+`SEED_CONNECTIONS` need setting.
+
+Headers through the seed API (`SEED_FETCH=relay`, the default) use the
+indexer's news server account: `SEED_NNTP_CONNECTIONS` in the indexer's
+`.env` sets how many connections it fetches with for all nodes together.
+With `SEED_FETCH=direct` a node uses its own NNTP account instead (fill in
+the NNTP lines in `node.env`).
 
 ## What a node needs
 

seed-node/node.env.example

@@ -1,17 +1,19 @@
 # --- Seed API: the orchestrator, and this node's token (`node ace seed:token <name>` on the indexer).
 SEED_URL=https://seed.exp.sforum.nl
 SEED_TOKEN=sn_replace_me
-# Ranges worked on at once; each uses one NNTP connection of the account below.
-SEED_CONNECTIONS=2
+# Ranges worked on at once (about 0.4 CPU core each).
+SEED_CONNECTIONS=4
+# relay: headers come through the seed API, no news server account needed (the default).
+# direct: the node fetches with its own NNTP account; then fill in the NNTP_* lines below.
+SEED_FETCH=relay
 
-# --- NNTP account this node fetches headers with (mind its connection limit across all nodes).
-NNTP_HOST=news.example.com
+# --- Only for SEED_FETCH=direct: the NNTP account (counts against its connection and IP limits).
+NNTP_HOST=localhost
 NNTP_PORT=563
 NNTP_SECURE=true
-NNTP_USER=replace_me
-NNTP_PASSWORD=replace_me
-# Only when NNTP_HOST is a tunnel or proxy (e.g. localhost:1563 forwarded to news.eweka.nl:563):
-# the hostname the server's TLS certificate is for.
+NNTP_USER=unused
+NNTP_PASSWORD=unused
+# Through a tunnel or proxy: the hostname the server's TLS certificate is for.
 # NNTP_TLS_SERVERNAME=news.eweka.nl
 
 # --- Required by the app's configuration, but unused on a seeding node (no database, Redis or web server).

start/env.ts

@@ -49,6 +49,7 @@ export default await Env.create(new URL('../', import.meta.url), {
   NNTP_POOL_SIZE: Env.schema.number.optional(),
   NNTP_COMMAND_TIMEOUT_MS: Env.schema.number.optional(),
   NNTP_TLS_SERVERNAME: Env.schema.string.optional(),
+  SEED_NNTP_CONNECTIONS: Env.schema.number.optional(),
 
   // Indexer (config/indexer.ts)
   BACKFILL_MAX_QUEUED: Env.schema.number.optional(),

start/routes.ts

@@ -55,6 +55,7 @@ router
   .group(() => {
     router.post('lease', [SeedController, 'lease'])
     router.post('ranges/:id/batches', [SeedController, 'batch']).where('id', router.matchers.number())
+    router.get('ranges/:id/chunk', [SeedController, 'chunk']).where('id', router.matchers.number())
     router.post('ranges/:id/done', [SeedController, 'done']).where('id', router.matchers.number())
     router.post('ranges/:id/release', [SeedController, 'release']).where('id', router.matchers.number())
     router.get('status', [SeedController, 'status'])

tests/functional/seed_api.spec.ts

@@ -5,6 +5,8 @@ import testUtils from '@adonisjs/core/services/test_utils'
 import SeedOrchestrator from '#services/SeedOrchestrator'
 import QueueService from '#services/QueueService'
 import indexerConfig from '#config/indexer'
+import SeedFetchPool from '#services/SeedFetchPool'
+import { deflateSync } from 'node:zlib'
 import { segmentFromHeader } from '#lib/ingest/segment'
 import { FileAggregator } from '#lib/aggregate/index'
 import { toFragment, toSeedFile, type SeedBatch } from '#lib/seed/wire'
@@ -99,4 +101,31 @@ test.group('Seed API', (group) => {
     assert.equal(row.status, 'queued')
     assert.equal(row.attempts, 0)
   })
+
+  test('relay: a leased range gets its overview chunks through the API', async ({ client, assert }) => {
+    const token = await SeedOrchestrator.issueToken('relay-node')
+    await db.table('seed_ranges').insert({ group_name: 'alt.binaries.test', start_id: 1, end_id: 100, next_id: 1 })
+    const auth = { authorization: `Bearer ${token}` }
+    const range = (await client.post('/api/v1/seed/lease').headers(auth)).body().range
+    const fetch = SeedFetchPool.fetch
+    const connections = indexerConfig.seed.nntpConnections
+    const asked: unknown[] = []
+    SeedFetchPool.fetch = async (group, from, to) => {
+      asked.push([group, from, to])
+      return deflateSync(Buffer.from('5\tsubject\r\n'))
+    }
+    try {
+      indexerConfig.seed.nntpConnections = 0
+      ;(await client.get(`/api/v1/seed/ranges/${range.id}/chunk`).qs({ from: 1, to: 50 }).headers(auth)).assertStatus(503)
+      indexerConfig.seed.nntpConnections = 1
+      const chunk = await client.get(`/api/v1/seed/ranges/${range.id}/chunk`).qs({ from: 50, to: 500 }).headers(auth)
+      chunk.assertStatus(200)
+      // Clamped to the range.
+      assert.deepEqual(asked, [['alt.binaries.test', 50, 100]])
+      ;(await client.get(`/api/v1/seed/ranges/${range.id}/chunk`).qs({ from: 200, to: 300 }).headers(auth)).assertStatus(400)
+    } finally {
+      SeedFetchPool.fetch = fetch
+      indexerConfig.seed.nntpConnections = connections
+    }
+  })
 })

tests/unit/xover_client.spec.ts

@@ -2,6 +2,7 @@ import { test } from '@japa/runner'
 import net from 'node:net'
 import { deflateSync } from 'node:zlib'
 import { XoverClient, parseOverviews } from '#lib/nntp/xover_client'
+import { unzipSync } from 'node:zlib'
 
 const LINES = [
   '101\tShow.S01E01 - "a.mkv" yEnc (1/2)\tposter <p@x>\tMon, 05 Oct 2026 10:00:00 +0000\t<one@test>\t\t700000\t5000\tXref: news.example a.b.test:101',
@@ -86,4 +87,20 @@ test.group('nntp / XoverClient', () => {
       close()
     }
   })
+
+  for (const compress of [false, true]) {
+    test(`hands out overviews as one zlib stream (${compress ? 'as the server sent it' : 'deflated here'})`, async ({ assert }) => {
+      const { port, close } = await server()
+      const client = await XoverClient.connect({ host: '127.0.0.1', port, user: 'u', password: 'p', compress })
+      try {
+        await client.group('a.b.test')
+        const raw = await client.xoverRaw(101, 102)
+        assert.deepEqual(parseOverviews(unzipSync(raw).toString('utf8')).map(([n]) => n), [101, 102])
+        assert.lengthOf(parseOverviews(unzipSync(await client.xoverRaw(1, 1)).toString('utf8')), 0)
+      } finally {
+        client.close()
+        close()
+      }
+    })
+  }
 })