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'use strict';
var _types = require('../types');
/**
* Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*/
let file = null;
let setupArgs = [];
let initialized = false;
/**
* This file is a small bootstrapper for workers. It sets up the communication
* between the worker and the parent process, interpreting parent messages and
* sending results back.
*
* The file loaded will be lazily initialized the first time any of the workers
* is called. This is done for optimal performance: if the farm is initialized,
* but no call is made to it, child Node processes will be consuming the least
* possible amount of memory.
*
* If an invalid message is detected, the child will exit (by throwing) with a
* non-zero exit code.
*/
const messageListener = request => {
switch (request[0]) {
case _types.CHILD_MESSAGE_INITIALIZE:
const init = request;
file = init[2];
setupArgs = request[3];
break;
case _types.CHILD_MESSAGE_CALL:
const call = request;
execMethod(call[2], call[3]);
break;
case _types.CHILD_MESSAGE_END:
end();
break;
default:
throw new TypeError(
'Unexpected request from parent process: ' + request[0]
);
}
};
process.on('message', messageListener);
function reportSuccess(result) {
if (!process || !process.send) {
throw new Error('Child can only be used on a forked process');
}
process.send([_types.PARENT_MESSAGE_OK, result]);
}
function reportClientError(error) {
return reportError(error, _types.PARENT_MESSAGE_CLIENT_ERROR);
}
function reportInitializeError(error) {
return reportError(error, _types.PARENT_MESSAGE_SETUP_ERROR);
}
function reportError(error, type) {
if (!process || !process.send) {
throw new Error('Child can only be used on a forked process');
}
if (error == null) {
error = new Error('"null" or "undefined" thrown');
}
process.send([
type,
error.constructor && error.constructor.name,
error.message,
error.stack,
typeof error === 'object' ? {...error} : error
]);
}
function end() {
const main = require(file);
if (!main.teardown) {
exitProcess();
return;
}
execFunction(main.teardown, main, [], exitProcess, exitProcess);
}
function exitProcess() {
// Clean up open handles so the process ideally exits gracefully
process.removeListener('message', messageListener);
}
function execMethod(method, args) {
const main = require(file);
let fn;
if (method === 'default') {
fn = main.__esModule ? main['default'] : main;
} else {
fn = main[method];
}
function execHelper() {
execFunction(fn, main, args, reportSuccess, reportClientError);
}
if (initialized || !main.setup) {
execHelper();
return;
}
initialized = true;
execFunction(main.setup, main, setupArgs, execHelper, reportInitializeError);
}
const isPromise = obj =>
!!obj &&
(typeof obj === 'object' || typeof obj === 'function') &&
typeof obj.then === 'function';
function execFunction(fn, ctx, args, onResult, onError) {
let result;
try {
result = fn.apply(ctx, args);
} catch (err) {
onError(err);
return;
}
if (isPromise(result)) {
result.then(onResult, onError);
} else {
onResult(result);
}
}