Seed relay: a stalled compressed XOVER is fetched again uncompressed

The four ranges kept failing on fresh connections too: in gzip mode Eweka
stops some chunks partway (a.b.ath 49701720000: 19,672 of 20,000
overviews, the last line cut, then silence), while the same chunk without
compression comes in 0.3 s. A failed relay chunk is now retried once
without compression on a connection of its own (dead pooled connections are
covered by the same retry).

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

app/services/SeedFetchPool.ts

@@ -30,15 +30,45 @@ class SeedFetchPool {
     return indexerConfig.seed.nntpConnections
   }
 
-  /** Retried once on a fresh connection: a failure is nearly always a dead connection, not the articles. */
+  /**
+   * A failure is retried once without compression, on a connection of its
+   * own: either the pooled connection was dead (dropped while idle), or the
+   * server stalled mid-reply in compressed mode. Eweka does that for some
+   * chunks: it stops after most of the stream and never sends the rest
+   * (a.b.ath 49701720000: 19,672 of 20,000 overviews, then silence), while
+   * the same chunk uncompressed comes in 0.3 s (LOG.md 2026-10-05 (11)).
+   */
   async fetch(group: string, from: number, to: number): Promise<Buffer> {
     try {
       return await this.fetchOnce(group, from, to)
     } catch {
-      return this.fetchOnce(group, from, to)
+      return this.fetchPlain(group, from, to)
     }
   }
 
+  private async fetchPlain(group: string, from: number, to: number): Promise<Buffer> {
+    const client = await this.connect(false)
+    try {
+      await client.group(group)
+      return await client.xoverRaw(from, to)
+    } finally {
+      client.close()
+    }
+  }
+
+  private connect(compress: boolean) {
+    return XoverClient.connect({
+      host: nntpConfig.host,
+      port: nntpConfig.port,
+      secure: nntpConfig.secure,
+      servername: nntpConfig.tlsServername,
+      user: nntpConfig.user,
+      password: nntpConfig.password?.release(),
+      timeoutMs: indexerConfig.seed.nntpTimeoutMs,
+      compress,
+    })
+  }
+
   private async fetchOnce(group: string, from: number, to: number): Promise<Buffer> {
     const slot = await this.acquire()
     let ok = false
@@ -75,17 +105,7 @@ class SeedFetchPool {
       if (this.open < this.size) {
         this.open++
         try {
-          const client = await XoverClient.connect({
+          return { client: await this.connect(true), usedAt: Date.now() }
-            host: nntpConfig.host,
-            port: nntpConfig.port,
-            secure: nntpConfig.secure,
-            servername: nntpConfig.tlsServername,
-            user: nntpConfig.user,
-            password: nntpConfig.password?.release(),
-            timeoutMs: indexerConfig.seed.nntpTimeoutMs,
-            compress: true,
-          })
-          return { client, usedAt: Date.now() }
         } catch (error) {
           this.open--
           this.waiters.shift()?.()

tests/unit/seed_fetch_pool.spec.ts

@@ -7,8 +7,9 @@ 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 }) => {
+  test('a chunk that fails (dead connection, stalled compressed reply) is fetched again uncompressed', async ({ assert }) => {
     let connections = 0
+    const compressAsked: Record<number, boolean> = {}
     const server = net.createServer((sock) => {
       const n = ++connections
       sock.write('200 welcome\r\n')
@@ -16,7 +17,7 @@ test.group('SeedFetchPool', () => {
         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('XFEATURE')) (compressAsked[n] = true), 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()
@@ -32,6 +33,8 @@ test.group('SeedFetchPool', () => {
       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)
+      // The pooled connection asked for gzip; the retry didn't.
+      assert.deepEqual(compressAsked, { 1: true })
     } finally {
       SeedFetchPool.closeIdle()
       Object.assign(nntpConfig, { host: saved.host, port: saved.port, secure: saved.secure })