Blame · child.ts

b69ab31	1	/**
b69ab31	2	* Copyright (c) Meta Platforms, Inc. and affiliates.
b69ab31	3	*
b69ab31	4	* This source code is licensed under the MIT license found in the
b69ab31	5	* LICENSE file in the root directory of this source tree.
b69ab31	6	*/
b69ab31	7
b69ab31	8	/**
b69ab31	9	* This file is expected to be run via child_process.fork() where:
b69ab31	10	*
b69ab31	11	* - The arguments to `startServer()` are JSON-serialized as the value
b69ab31	12	* of the ISL_SERVER_ARGS environment variable.
b69ab31	13	* - Communication to the parent process must be done via process.send()
b69ab31	14	* and the parent process expects messages that conform to
b69ab31	15	* `ChildProcessResponse`.
b69ab31	16	*/
b69ab31	17
b69ab31	18	import type {StartServerArgs, StartServerResult} from './server';
b69ab31	19
b69ab31	20	import * as fs from 'node:fs';
b69ab31	21
b69ab31	22	/**
b69ab31	23	* This defines the shape of the messages that the parent process accepts.
b69ab31	24	* As such, it is imperative that these types are serializable.
b69ab31	25	*/
b69ab31	26	export type ChildProcessResponse =
b69ab31	27	\| {
b69ab31	28	type: 'message';
b69ab31	29	args: Parameters<typeof console.log>;
b69ab31	30	}
b69ab31	31	\| {
b69ab31	32	type: 'result';
b69ab31	33	result: StartServerResult;
b69ab31	34	};
b69ab31	35
b69ab31	36	function sendMessageToParentProcess(msg: ChildProcessResponse): void {
b69ab31	37	process.send?.(msg, undefined, {swallowErrors: true});
b69ab31	38	}
b69ab31	39
b69ab31	40	function info(...args: Parameters<typeof console.log>): void {
b69ab31	41	const msg = {
b69ab31	42	type: 'message',
b69ab31	43	args,
b69ab31	44	} as ChildProcessResponse;
b69ab31	45	sendMessageToParentProcess(msg);
b69ab31	46	}
b69ab31	47
b69ab31	48	const args: StartServerArgs = JSON.parse(process.env.ISL_SERVER_ARGS as string);
b69ab31	49	args.logInfo = info;
b69ab31	50	import('./server')
b69ab31	51	.then(({startServer}) => startServer(args))
b69ab31	52	.then((result: StartServerResult) => {
b69ab31	53	sendMessageToParentProcess({type: 'result', result});
b69ab31	54	})
b69ab31	55	.catch(error =>
b69ab31	56	sendMessageToParentProcess({type: 'result', result: {type: 'error', error: String(error)}}),
b69ab31	57	);
b69ab31	58
b69ab31	59	process.on('uncaughtException', err => {
b69ab31	60	const {logFileLocation} = args;
b69ab31	61	fs.promises.appendFile(
b69ab31	62	logFileLocation,
b69ab31	63	`\n[${new Date().toString()}] ISL server child process got an uncaught exception:\n${
b69ab31	64	err?.stack ?? err?.message
b69ab31	65	}\n\n`,
b69ab31	66	'utf8',
b69ab31	67	);
b69ab31	68	});