22 lines
1.3 KiB
TypeScript
22 lines
1.3 KiB
TypeScript
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import { spawn } from "node:child_process";
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/** Kernel-owned lock: a crashed coordinator cannot leave a stale ownership file.
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* The persistent file is just an inode; EOF releases the helper's lock. */
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export async function withFileLock<T>(filename: string, work: () => Promise<T>): Promise<T> {
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const child = spawn("flock", ["--exclusive", "--nonblock", "--conflict-exit-code", "75", filename,
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process.execPath, "-e", 'process.stdout.write("locked\\n"); process.stdin.resume();'], {stdio: ["pipe", "pipe", "pipe"]});
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let diagnostics = "";
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child.stdin.on("error", () => { /* acquisition/exit handling reports helper failure */ });
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child.stderr.on("data", chunk => { diagnostics = (diagnostics + String(chunk)).slice(-2000); });
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const closed = new Promise<void>((resolve) => { child.once("close", () => resolve()); });
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try {
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await new Promise<void>((resolve, reject) => {
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let output = "";
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child.once("error", reject);
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child.once("exit", code => reject(new Error(code === 75 ? "Another authoring command owns this repository; retry when it finishes" : `Cannot acquire authoring lock: ${diagnostics}`)));
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child.stdout.on("data", chunk => { output += chunk; if (output.includes("locked\n")) resolve(); });
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});
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return await work();
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} finally { child.stdin.end(); await closed; }
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}
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