Seed relay: dead NNTP connections found in 90 s and retried

Five ranges "never answered" in 10 minutes, yet their chunk came back in
0.3 s on a fresh connection: the news server drops idle connections
without telling, and the pool's next request on one waited for the
10-minute inactivity timeout. Now: SEED_NNTP_TIMEOUT_MS 90 s (inactivity;
slow ranges keep streaming), one retry on a fresh connection, and pooled
connections idle over 60 s are replaced before use.

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

tests/unit/seed_fetch_pool.spec.ts

@@ -0,0 +1,42 @@
+import { test } from '@japa/runner'
+import net from 'node:net'
+import { unzipSync } from 'node:zlib'
+import nntpConfig from '#config/nntp'
+import indexerConfig from '#config/indexer'
+import SeedFetchPool from '#services/SeedFetchPool'
+import { parseOverviews } from '#lib/nntp/xover_client'
+
+test.group('SeedFetchPool', () => {
+  test('a chunk that fails on a dead connection is fetched again on a fresh one', async ({ assert }) => {
+    let connections = 0
+    const server = net.createServer((sock) => {
+      const n = ++connections
+      sock.write('200 welcome\r\n')
+      sock.on('data', (chunk) => {
+        for (const line of chunk.toString().split('\r\n').filter(Boolean)) {
+          if (line.startsWith('AUTHINFO USER')) sock.write('381 more\r\n')
+          else if (line.startsWith('AUTHINFO PASS')) sock.write('281 ok\r\n')
+          else if (line.startsWith('XFEATURE')) sock.write('500 no\r\n')
+          else if (line.startsWith('GROUP')) sock.write('211 1 7 7 a.b.test\r\n')
+          // The first connection dies as the request arrives, like one the server dropped while idle.
+          else if (line.startsWith('XOVER') && n === 1) sock.destroy()
+          else if (line.startsWith('XOVER')) sock.write('224 overviews\r\n7\tsubject\tposter\tdate\t<a@b>\t\t10\t1\r\n.\r\n')
+        }
+      })
+    })
+    await new Promise<void>((resolve) => server.listen(0, '127.0.0.1', resolve))
+    const saved = { host: nntpConfig.host, port: nntpConfig.port, secure: nntpConfig.secure, connections: indexerConfig.seed.nntpConnections }
+    Object.assign(nntpConfig, { host: '127.0.0.1', port: (server.address() as net.AddressInfo).port, secure: false })
+    indexerConfig.seed.nntpConnections = 2
+    try {
+      const raw = await SeedFetchPool.fetch('a.b.test', 7, 7)
+      assert.deepEqual(parseOverviews(unzipSync(raw).toString('utf8')).map(([n]) => n), [7])
+      assert.equal(connections, 2)
+    } finally {
+      SeedFetchPool.closeIdle()
+      Object.assign(nntpConfig, { host: saved.host, port: saved.port, secure: saved.secure })
+      indexerConfig.seed.nntpConnections = saved.connections
+      server.close()
+    }
+  })
+})