Bug: persistence.list() walks every session directory one libuv round-trip at a time (~2.3k event-loop turns per call), and session_trace has no timeoutMs

[longjucheng]

中文摘要 — SessionCorpus.listSessions、filterSessions 授权、以及 readSession 的持久化分支，每次调用都对 ~/.dsh/sessions 全库逐目录串行 I/O（readdir → open/read/zstd/close → stat；库里有 pre-v4 日志时 historicalCorpusRevision 再走一遍），一次约 2.3k 个事件循环轮、无并发、无缓存。事件循环空闲时 0.1 s；每轮多 10 ms 阻塞时 23 s，25 ms 时 57 s。session_trace 注册时没有 timeoutMs，两个 search 工具有 searchTimeoutMs。

Summary

Three paths list the whole persisted store before their own work, and the listing is strictly sequential:

• session_trace → sessionQuery.traceSession → SessionCorpus.listSessions → persistence.list() (packages/session-query/session-query/src/index.ts:327–331, corpus.ts:61–80);
• session_event_read on a non-caller target → authorizeTarget → filterSessions → the same listing (packages/session-query/tool-session-query/src/workspace-access.ts:85); then readEvent → SessionCorpus.load → the listing again when the session is not live (session-query/src/index.ts:370);
• sessionQuery.readSession(id) of a non-live session → SessionCorpus.load → persistence.list() before the one log is read (corpus.ts:91–98).

JsonlSessionPersistence.list() (packages/session/session-persistence-jsonl/src/index.ts:475–509) runs listArtifacts (:1056–1084: per directory readdir, then open + read + zstdDecompress + close for the header line (readFirstZstdLine, :1410–1444), then realpath when needed), then historicalCorpusRevision (:1038–1054: a second full listGenerations pass plus one stat per log while pre-v4 logs remain), then one stat per artifact. Each step is one libuv round-trip; none run concurrently. Wall time is turns × event-loop turn cost.

session_trace is registered without timeoutMs (packages/session-query/tool-session-query/src/index.ts:85–93); the two search tools take searchTimeoutMs. The cost scales with store size × loop delay, not with lineage size.

Reproduction (offline, no session content)

// node bench.mjs <copy-of-~/.dsh/sessions> <blockMs>
import { createRequire } from 'node:module'
import { pathToFileURL } from 'node:url'
import { createHook } from 'node:async_hooks'
const PKG = '<checkout>/packages/session/session-persistence-jsonl'
const req = createRequire(PKG + '/package.json')
const { Context } = await import(pathToFileURL(req.resolve('@deepseek-ai/cordis')).href)
const { default: Jsonl } = await import(pathToFileURL(PKG + '/lib/index.js').href)
const [root, blockMs] = [process.argv[2], Number(process.argv[3] ?? 0)]
const ctx = new Context()
await ctx.plugin(Jsonl, { root, compression: 'zstd' })
await new Promise(r => setTimeout(r, 200))
let turns = 0
createHook({ init(_id, type) { if (type === 'Immediate') turns++ } }).enable()
if (blockMs > 0) { const spin = () => { const end = Date.now() + blockMs; while (Date.now() < end); setImmediate(spin) }; setImmediate(spin) }
const t0 = performance.now()
const n = (await ctx.sessionPersistence.list()).length
console.log({ blockMs, sessions: n, listMs: Math.round(performance.now() - t0), loopTurns: turns })
process.exit(0)

Copy of a 228-session, 89 MB store:

emulated per-turn block	list() wall time
0 ms	102–125 ms
10 ms	22.9 s
25 ms	57.3 s

Per call: ~1.6k FSREQPROMISE, 228 ZLIB, 228 FILEHANDLECLOSEREQ, ~2.29k event-loop turns.

Current behavior

On a host whose event loop was congested (the heap-growth phase of #7414), session_trace {} took 447 s (aborted) and 558.7 s (retry, ok); session_event_read on a non-live session took 1428.7 s (two listings). No timeout applies. After a restart the same calls return in under a second.

Expected behavior

• Reading one session by id does not enumerate the store (load's live branch does not; observeSession caches one id by revision).
• The directory walk runs with bounded concurrency and/or is cached by corpus revision; the pre-v4 second pass is a one-time migration or cached.
• session_trace takes timeoutMs like the search tools.

Related: #7414 (comment "Cold-corpus re-enumeration": the same walk measured from the I/O side); #7356 (readEvent deep-clones the whole session on the live branch; this report is the persisted branch).

Environment

• @deepseek-ai/dsh source checkout at tag dsh-v0.2.0-rc.1, dev launch pnpm dsh web (node --import tsx/esm apps/cli/src/bin.ts web)
• Node v22.23.1, macOS 15.7.5 (arm64)
• Store: ~230 session directories, ~90 MB zstd JSONL, pre-v4 logs (session.jsonl.zstd, .v2, .v3) present