55 lines
1.6 KiB
TypeScript
55 lines
1.6 KiB
TypeScript
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(
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"flock",
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[
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"--exclusive",
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"--timeout",
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"120",
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"--conflict-exit-code",
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"75",
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filename,
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process.execPath,
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"-e",
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'process.stdout.write("locked\\n"); process.stdin.resume();',
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],
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{ stdio: ["pipe", "pipe", "pipe"] },
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);
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let diagnostics = "";
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child.stdin.on("error", () => {
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/* acquisition/exit handling reports helper failure */
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});
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child.stderr.on("data", (chunk) => {
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diagnostics = (diagnostics + String(chunk)).slice(-2000);
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});
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const closed = new Promise<void>((resolve) => {
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child.once("close", () => resolve());
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});
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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) =>
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reject(
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new Error(
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code === 75
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? "Timed out after 120 seconds waiting for another authoring command; inspect that command before retrying"
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: `Cannot acquire authoring lock: ${diagnostics}`,
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),
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),
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);
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child.stdout.on("data", (chunk) => {
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output += chunk;
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if (output.includes("locked\n")) resolve();
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});
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});
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return await work();
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} finally {
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child.stdin.end();
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await closed;
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}
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}
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