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fix: Make caching work correctly in async context
BREAKING CHANGE: The file-IO caches now contains promises instead of the actual result. Previously the cache was only populated after the function call succeed which in a async context was leading to multiple file IO or analyze tasks started for the same file at once. Caching the Promise instead of the result makes this problem go away.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,116 @@ | ||
| import type { Stats } from "fs"; | ||
| import { resolve } from "path"; | ||
| import fs from "graceful-fs"; | ||
| import { Sema } from "async-sema"; | ||
|
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| const fsReadFile = fs.promises.readFile; | ||
| const fsReadlink = fs.promises.readlink; | ||
| const fsStat = fs.promises.stat; | ||
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| export class CachedFileSystem { | ||
| private fileCache: Map<string, Promise<string | null>>; | ||
| private statCache: Map<string, Promise<Stats | null>>; | ||
| private symlinkCache: Map<string, Promise<string | null>>; | ||
| private fileIOQueue: Sema; | ||
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| constructor({ | ||
| cache, | ||
| fileIOConcurrency, | ||
| }: { | ||
| cache?: any; | ||
| fileIOConcurrency: number; | ||
| }) { | ||
| this.fileIOQueue = new Sema(fileIOConcurrency); | ||
| this.fileCache = (cache && cache.fileCache) || new Map(); | ||
| this.statCache = (cache && cache.statCache) || new Map(); | ||
| this.symlinkCache = (cache && cache.symlinkCache) || new Map(); | ||
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| if (cache) { | ||
| cache.fileCache = this.fileCache; | ||
| cache.statCache = this.statCache; | ||
| cache.symlinkCache = this.symlinkCache; | ||
| } | ||
| } | ||
|
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| async readlink(path: string): Promise<string | null> { | ||
| const cached = this.symlinkCache.get(path); | ||
| if (cached !== undefined) return cached; | ||
| // This is not awaiting the response, so that the cache is instantly populated and | ||
| // future calls serve the Promise from the cache | ||
| const readlinkPromise = this.executeFileIO(path, this._internalReadlink); | ||
| this.symlinkCache.set(path, readlinkPromise); | ||
|
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| return readlinkPromise; | ||
| } | ||
|
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| async readFile(path: string): Promise<string | null> { | ||
| const cached = this.fileCache.get(path); | ||
| if (cached !== undefined) return cached; | ||
| // This is not awaiting the response, so that the cache is instantly populated and | ||
| // future calls serve the Promise from the cache | ||
| const readFilePromise = this.executeFileIO(path, this._internalReadFile); | ||
| this.fileCache.set(path, readFilePromise); | ||
|
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| return readFilePromise; | ||
| } | ||
|
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| async stat(path: string): Promise<Stats | null> { | ||
| const cached = this.statCache.get(path); | ||
| if (cached !== undefined) return cached; | ||
| // This is not awaiting the response, so that the cache is instantly populated and | ||
| // future calls serve the Promise from the cache | ||
| const statPromise = this.executeFileIO(path, this._internalStat); | ||
| this.statCache.set(path, statPromise); | ||
|
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| return statPromise; | ||
| } | ||
|
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| private async _internalReadlink(path: string) { | ||
| try { | ||
| const link = await fsReadlink(path); | ||
| // also copy stat cache to symlink | ||
| const stats = this.statCache.get(path); | ||
| if (stats) this.statCache.set(resolve(path, link), stats); | ||
| return link; | ||
| } catch (e: any) { | ||
| if (e.code !== "EINVAL" && e.code !== "ENOENT" && e.code !== "UNKNOWN") | ||
| throw e; | ||
| return null; | ||
| } | ||
| } | ||
|
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||
| private async _internalReadFile(path: string): Promise<string | null> { | ||
| try { | ||
| return (await fsReadFile(path)).toString(); | ||
| } catch (e: any) { | ||
| if (e.code === "ENOENT" || e.code === "EISDIR") { | ||
| return null; | ||
| } | ||
| throw e; | ||
| } | ||
| } | ||
|
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||
| private async _internalStat(path: string) { | ||
| try { | ||
| return await fsStat(path); | ||
| } catch (e: any) { | ||
| if (e.code === "ENOENT") { | ||
| return null; | ||
| } | ||
| throw e; | ||
| } | ||
| } | ||
|
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| private async executeFileIO<Return>( | ||
| path: string, | ||
| fileIO: (path: string) => Promise<Return> | ||
| ): Promise<Return> { | ||
| await this.fileIOQueue.acquire(); | ||
|
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||
| try { | ||
| return fileIO.call(this, path); | ||
| } finally { | ||
| this.fileIOQueue.release(); | ||
| } | ||
| } | ||
| } |
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