Rebuild: the coordinator spools replies without inflating them

On homelab (1 Gbit, 20 connections, ~630k articles/s) the coordinator
used 1.3-1.7 cores, mostly GC of the text it inflated only to know a
compressed reply was complete, plus a copy of every reply. A raw reply
is now complete when it ends in ".\r\n" (no copy): 0.4-0.5 cores at
the same rate.

".\r\n" can also end a network read inside the compressed data (~1 in
16M reads, a few dozen times over the whole target). Such a chunk
doesn't inflate on the worker: it reports it (POST ranges/:id/corrupt),
the spooled chunk is removed and the range goes back to the queue; the
prefetcher fetches it again. The rest of that reply breaks the
connection's next command, so the connection is replaced.

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

app/services/leases.ts

@@ -58,6 +58,18 @@ class Leases {
     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)
+    await db.from('ranges').where('id', rangeId).update({ status: 'planned', node_id: null })
+  }
+
   /** A stopping worker gives its range back; the next one resumes it. */
   async release(rangeId: number, nodeId: number) {
     await this.leased(rangeId, nodeId)

app/services/spool.ts

@@ -53,6 +53,11 @@ class Spool {
     return readFile(this.path(rangeId, span))
   }
 
+  /** One chunk, e.g. one that doesn't inflate (a false end of reply; see XoverClient.compressedRaw). */
+  async removeChunk(rangeId: number, span: ChunkSpan) {
+    await rm(this.path(rangeId, span), { force: true })
+  }
+
   async remove(rangeId: number) {
     await rm(join(this.dir, String(rangeId)), { recursive: true, force: true })
   }