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mitigating the problem with unreachable UNC paths by leaving at least one slot available for local operations #1115
Massimo Melina committed
Nov 2, 2025 at 16:18 UTC
7f56fbbe4f99942d7a8c0b6d2e6975d7866d501a
3 files changed
+51
-18
src/stat.ts
new
+42
@@ -0,0 +1,42 @@
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+import { defineConfig } from './config'
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+import { Stats } from 'node:fs'
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+import { haveTimeout, pendingPromise } from './cross'
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+import { stat } from 'fs/promises'
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+
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+const fileTimeout = defineConfig('file_timeout', 3, x => x * 1000)
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+
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+// since nodejs' UV_THREADPOOL_SIZE is limited, avoid using multiple slots for the same UNC host, and always leave one free for local operations
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+const poolSize = Number(process.env.UV_THREADPOOL_SIZE || 4)
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+const previous = new Map<string, Promise<Stats>>() // wrapped promises with haveTimeout
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+const working = new Set<Promise<Stats>>() // plain stat's promise
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+export async function statWithTimeout(path: string) {
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+ const uncHost = /^\\\\([^\\]+)\\/.exec(path)?.[1]
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+ if (!uncHost)
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+ return haveTimeout(fileTimeout.compiled(), stat(path))
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+ const busy = process.env.HFS_PARALLEL_UNC ? null : previous.get(uncHost) // by default we serialize requests on the same UNC host, to keep threadpool usage low
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+ const ret = pendingPromise<Stats>()
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+ previous.set(uncHost, ret) // reserve the slot before starting the operation
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+ const err = await busy?.then(() => false, e => e.message === 'timeout' && e) // only timeout error is shared with pending requests
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+ if (err) {
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+ if (previous.get(uncHost) === ret) // but we don't want to block forever, only involve those that were already waiting
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+ previous.delete(uncHost)
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+ ret.reject(err)
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+ return ret
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+ }
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+ while (working.size >= poolSize - 1) // always leave one slot free for local operations
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+ await Promise.race(working.values()).catch(() => {}) // we are assuming UV_THREADPOOL_SIZE > 1, otherwise race() will deadlock
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+ const op = stat(path)
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+ working.add(op)
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+ try {
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+ ret.resolve(await haveTimeout(fileTimeout.compiled(),
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+ op.finally(() => working.delete(op)) ))
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+ }
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+ catch (e) {
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+ ret.reject(e)
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+ }
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+ finally {
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+ if (previous.get(uncHost) === ret)
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+ previous.delete(uncHost)
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+ }
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+ return ret
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+}
src/util-files.ts
+5
-17
@@ -1,30 +1,18 @@
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// This file is part of HFS - Copyright 2021-2023, Massimo Melina <a@rejetto.com> - License https://www.gnu.org/licenses/gpl-3.0.txt
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-import { access, mkdir, readFile, stat } from 'fs/promises'
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-import { Promisable, try_, wait, isWindowsDrive, haveTimeout, splitAt } from './cross'
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-import { defineConfig } from './config'
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+import { access, mkdir, readFile } from 'fs/promises'
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+import { Promisable, try_, wait, isWindowsDrive } from './cross'
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import { createWriteStream, mkdirSync, watch, ftruncate } from 'fs'
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import { basename, dirname } from 'path'
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import glob from 'fast-glob'
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import { IS_WINDOWS } from './const'
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import { once } from 'events'
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import { Readable } from 'stream'
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+import { statWithTimeout } from './stat'
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// @ts-ignore
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import unzipper from 'unzip-stream'
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-const fileTimeout = defineConfig('file_timeout', 3, x => x * 1000)
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-
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-// since nodejs' UV_THREADPOOL_SIZE is 4 by default, avoid using multiple slots for the same UNC host. This doesn't solve the problem but at least mitigates it.
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-const uncStatWaiting = new Map<string, Promise<any>>()
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-export async function statWithTimeout(path: string) {
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- const uncHost = path.startsWith('\\\\') && splitAt('\\', path.slice(2))[0]
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- if (uncHost)
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- await uncStatWaiting.get(uncHost)
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- const op = stat(path)
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- if (uncHost)
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- uncStatWaiting.set(uncHost, op.finally(() => uncStatWaiting.delete(uncHost)).catch(() => {}))
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- return haveTimeout(fileTimeout.compiled(), op)
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-}
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+export { statWithTimeout }
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export async function isDirectory(path: string) {
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try { return (await statWithTimeout(path)).isDirectory() }
@@ -174,4 +162,4 @@ export async function parseFile<T>(path: string, parse: (path: string) => T) {
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export async function parseFileContent<T>(path: string, parse: (raw: Buffer) => T) {
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return parseFile(path, () => readFile(path).then(parse))
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-}
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+}
\ No newline at end of file
src/vfs.ts
+4
-1
@@ -172,7 +172,10 @@ export async function getNodeByName(name: string, parent: VfsNode) {
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}
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export let vfs: VfsNode = {}
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-defineConfig('vfs', vfs).sub(reviewVfs)
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+defineConfig('vfs', vfs).sub(async x => {
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+ await reviewVfs(x)
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+ console.log('VFS ready')
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+})
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async function reviewVfs(data=vfs) {
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await (async function recur(node) {