89 lines
2.8 KiB
TypeScript
89 lines
2.8 KiB
TypeScript
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// https://gist.github.com/nfantone/1eaa803772025df69d07f4dbf5df7e58
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'use strict';
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/**
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* @callback BeforeShutdownListener
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* @param {string} [signalOrEvent] The exit signal or event name received on the process.
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*/
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/**
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* System signals the app will listen to initiate shutdown.
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* @const {string[]}
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*/
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const SHUTDOWN_SIGNALS = ['SIGINT', 'SIGTERM'];
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/**
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* Time in milliseconds to wait before forcing shutdown.
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* @const {number}
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*/
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const SHUTDOWN_TIMEOUT = 15000;
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/**
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* A queue of listener callbacks to execute before shutting
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* down the process.
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* @type {BeforeShutdownListener[]}
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*/
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const shutdownListeners = [];
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/**
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* Listen for signals and execute given `fn` function once.
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* @param {string[]} signals System signals to listen to.
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* @param {function(string)} fn Function to execute on shutdown.
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*/
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const processOnce = (signals, fn) => {
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return signals.forEach(sig => process.once(sig, fn));
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};
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/**
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* Sets a forced shutdown mechanism that will exit the process after `timeout` milliseconds.
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* @param {number} timeout Time to wait before forcing shutdown (milliseconds)
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*/
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const forceExitAfter = timeout => () => {
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setTimeout(() => {
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// Force shutdown after timeout
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console.warn(`Could not close resources gracefully after ${timeout}ms: forcing shutdown`);
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return process.exit(1);
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}, timeout).unref();
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};
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/**
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* Main process shutdown handler. Will invoke every previously registered async shutdown listener
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* in the queue and exit with a code of `0`. Any `Promise` rejections from any listener will
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* be logged out as a warning, but won't prevent other callbacks from executing.
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* @param {string} signalOrEvent The exit signal or event name received on the process.
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*/
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async function shutdownHandler(signalOrEvent) {
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console.warn(`Shutting down: received [${signalOrEvent}] signal`);
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for (const listener of shutdownListeners) {
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try {
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await listener(signalOrEvent);
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} catch (err) {
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console.warn(`A shutdown handler failed before completing with: ${err.message || err}`);
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}
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}
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return process.exit(0);
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}
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/**
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* Registers a new shutdown listener to be invoked before exiting
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* the main process. Listener handlers are guaranteed to be called in the order
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* they were registered.
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* @param {BeforeShutdownListener} listener The shutdown listener to register.
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* @returns {BeforeShutdownListener} Echoes back the supplied `listener`.
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*/
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export function beforeShutdown(listener) {
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shutdownListeners.push(listener);
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return listener;
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}
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// Register shutdown callback that kills the process after `SHUTDOWN_TIMEOUT` milliseconds
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// This prevents custom shutdown handlers from hanging the process indefinitely
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processOnce(SHUTDOWN_SIGNALS, forceExitAfter(SHUTDOWN_TIMEOUT));
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// Register process shutdown callback
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// Will listen to incoming signal events and execute all registered handlers in the stack
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processOnce(SHUTDOWN_SIGNALS, shutdownHandler);
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