Kjell Tore Guttormsen
4a615b10ce
Foundation lib for status-fil + lock-fil writes in v1.12.0 cron rewrite. Pattern: writeFileSync to <path>.tmp.<pid>.<random> then renameSync to target. Defends against half-written files; readers either see the previous version or the new one, never a partial. - atomicWriteSync(path, content) — string or Buffer - atomicWriteJson(path, obj) — 2-space indent, trailing newline - Windows EEXIST/EPERM defensive fallback (unlink target + rename) - Best-effort tmp cleanup on writeFileSync failure - crypto.randomInt(0, 2**32) two-arg form (unambiguous across Node) 9/9 tests pass including 50-way concurrent-write fuzzer (async-aware withTmp helper). Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
53 lines
1.5 KiB
JavaScript
53 lines
1.5 KiB
JavaScript
// atomic-write.mjs — Crash-safe writes via tmp+rename.
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// Zero dependencies. Defends against half-written files; readers either see
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// the previous version or the new one, never a partial.
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import { writeFileSync, renameSync, unlinkSync } from 'node:fs';
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import { randomInt } from 'node:crypto';
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/**
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* Atomically write content to filePath via a tmp file + rename.
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* @param {string} filePath — target absolute path
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* @param {string|Buffer} content — bytes to write
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*/
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export function atomicWriteSync(filePath, content) {
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if (!filePath || typeof filePath !== 'string') {
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throw new Error('atomicWriteSync: filePath required');
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}
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const tmp = `${filePath}.tmp.${process.pid}.${randomInt(0, 2 ** 32)}`;
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try {
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writeFileSync(tmp, content);
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try {
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renameSync(tmp, filePath);
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} catch (err) {
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// Windows ERROR_ALREADY_EXISTS / EPERM defensive fallback.
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if (err && (err.code === 'EEXIST' || err.code === 'EPERM')) {
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try {
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unlinkSync(filePath);
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} catch {
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// best-effort
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}
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renameSync(tmp, filePath);
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} else {
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throw err;
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}
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}
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} catch (err) {
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// Best-effort cleanup of the tmp file on failure.
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try {
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unlinkSync(tmp);
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} catch {
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// best-effort
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}
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throw err;
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}
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}
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/**
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* Atomically write a JSON-serialized object with 2-space indent.
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* @param {string} filePath
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* @param {unknown} obj
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*/
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export function atomicWriteJson(filePath, obj) {
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atomicWriteSync(filePath, JSON.stringify(obj, null, 2) + '\n');
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}
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