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child.js
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child.js
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// @flow
import type {
CallRequest,
WorkerDataResponse,
WorkerErrorResponse,
WorkerMessage,
WorkerRequest,
WorkerResponse,
ChildImpl,
} from './types';
import type {Async, IDisposable} from '@parcel/types';
import type {SharedReference} from './WorkerFarm';
import invariant from 'assert';
import nullthrows from 'nullthrows';
import Logger, {patchConsole, unpatchConsole} from '@parcel/logger';
import ThrowableDiagnostic, {anyToDiagnostic} from '@parcel/diagnostic';
import {deserialize} from '@parcel/core';
import bus from './bus';
import Profiler from './Profiler';
import _Handle from './Handle';
// The import of './Handle' should really be imported eagerly (with @babel/plugin-transform-modules-commonjs's lazy mode).
const Handle = _Handle;
type ChildCall = WorkerRequest & {|
resolve: (result: Promise<any> | any) => void,
reject: (error: any) => void,
|};
export class Child {
callQueue: Array<ChildCall> = [];
childId: ?number;
maxConcurrentCalls: number = 10;
module: ?any;
responseId: number = 0;
responseQueue: Map<number, ChildCall> = new Map();
loggerDisposable: IDisposable;
child: ChildImpl;
profiler: ?Profiler;
handles: Map<number, Handle> = new Map();
sharedReferences: Map<SharedReference, mixed> = new Map();
sharedReferencesByValue: Map<mixed, SharedReference> = new Map();
constructor(ChildBackend: Class<ChildImpl>) {
this.child = new ChildBackend(
m => {
this.messageListener(m);
},
() => this.handleEnd(),
);
// Monitior all logging events inside this child process and forward to
// the main process via the bus.
this.loggerDisposable = Logger.onLog(event => {
bus.emit('logEvent', event);
});
}
workerApi: {|
callMaster: (
request: CallRequest,
awaitResponse?: ?boolean,
) => Promise<mixed>,
createReverseHandle: (fn: (...args: Array<any>) => mixed) => Handle,
getSharedReference: (ref: SharedReference) => mixed,
resolveSharedReference: (value: mixed) => void | SharedReference,
runHandle: (handle: Handle, args: Array<any>) => Promise<mixed>,
|} = {
callMaster: (
request: CallRequest,
awaitResponse: ?boolean = true,
): Promise<mixed> => this.addCall(request, awaitResponse),
createReverseHandle: (fn: (...args: Array<any>) => mixed): Handle =>
this.createReverseHandle(fn),
runHandle: (handle: Handle, args: Array<any>): Promise<mixed> =>
this.workerApi.callMaster({handle: handle.id, args}, true),
getSharedReference: (ref: SharedReference) =>
this.sharedReferences.get(ref),
resolveSharedReference: (value: mixed) =>
this.sharedReferencesByValue.get(value),
};
messageListener(message: WorkerMessage): Async<void> {
if (message.type === 'response') {
return this.handleResponse(message);
} else if (message.type === 'request') {
return this.handleRequest(message);
}
}
send(data: WorkerMessage): void {
this.child.send(data);
}
async childInit(module: string, childId: number): Promise<void> {
// $FlowFixMe this must be dynamic
this.module = require(module);
this.childId = childId;
if (this.module.childInit != null) {
await this.module.childInit();
}
}
async handleRequest(data: WorkerRequest): Promise<void> {
let {idx, method, args, handle: handleId} = data;
let child = nullthrows(data.child);
const responseFromContent = (content: any): WorkerDataResponse => ({
idx,
child,
type: 'response',
contentType: 'data',
content,
});
const errorResponseFromError = (e: Error): WorkerErrorResponse => ({
idx,
child,
type: 'response',
contentType: 'error',
content: anyToDiagnostic(e),
});
let result;
if (handleId != null) {
try {
let fn = nullthrows(this.handles.get(handleId)?.fn);
result = responseFromContent(fn(...args));
} catch (e) {
result = errorResponseFromError(e);
}
} else if (method === 'childInit') {
try {
let [moduleName, childOptions] = args;
if (childOptions.shouldPatchConsole) {
patchConsole();
} else {
unpatchConsole();
}
result = responseFromContent(await this.childInit(moduleName, child));
} catch (e) {
result = errorResponseFromError(e);
}
} else if (method === 'startProfile') {
this.profiler = new Profiler();
try {
result = responseFromContent(await this.profiler.startProfiling());
} catch (e) {
result = errorResponseFromError(e);
}
} else if (method === 'endProfile') {
try {
let res = this.profiler ? await this.profiler.stopProfiling() : null;
result = responseFromContent(res);
} catch (e) {
result = errorResponseFromError(e);
}
} else if (method === 'takeHeapSnapshot') {
try {
let v8 = require('v8');
result = responseFromContent(
v8.writeHeapSnapshot(
'heap-' +
args[0] +
'-' +
(this.childId ? 'worker' + this.childId : 'main') +
'.heapsnapshot',
),
);
} catch (e) {
result = errorResponseFromError(e);
}
} else if (method === 'createSharedReference') {
let [ref, _value] = args;
let value =
_value instanceof ArrayBuffer
? // In the case the value is pre-serialized as a buffer,
// deserialize it.
deserialize(Buffer.from(_value))
: _value;
this.sharedReferences.set(ref, value);
this.sharedReferencesByValue.set(value, ref);
result = responseFromContent(null);
} else if (method === 'deleteSharedReference') {
let ref = args[0];
let value = this.sharedReferences.get(ref);
this.sharedReferencesByValue.delete(value);
this.sharedReferences.delete(ref);
result = responseFromContent(null);
} else {
try {
result = responseFromContent(
// $FlowFixMe
await this.module[method](this.workerApi, ...args),
);
} catch (e) {
result = errorResponseFromError(e);
}
}
try {
this.send(result);
} catch (e) {
result = this.send(errorResponseFromError(e));
}
}
handleResponse(data: WorkerResponse): void {
let idx = nullthrows(data.idx);
let contentType = data.contentType;
let content = data.content;
let call = nullthrows(this.responseQueue.get(idx));
if (contentType === 'error') {
invariant(typeof content !== 'string');
call.reject(new ThrowableDiagnostic({diagnostic: content}));
} else {
call.resolve(content);
}
this.responseQueue.delete(idx);
// Process the next call
this.processQueue();
}
// Keep in mind to make sure responses to these calls are JSON.Stringify safe
addCall(
request: CallRequest,
awaitResponse: ?boolean = true,
): Promise<mixed> {
// $FlowFixMe
let call: ChildCall = {
...request,
type: 'request',
child: this.childId,
// $FlowFixMe Added in Flow 0.121.0 upgrade in #4381
awaitResponse,
resolve: () => {},
reject: () => {},
};
let promise;
if (awaitResponse) {
promise = new Promise((resolve, reject) => {
call.resolve = resolve;
call.reject = reject;
});
}
this.callQueue.push(call);
this.processQueue();
return promise ?? Promise.resolve();
}
sendRequest(call: ChildCall): void {
let idx;
if (call.awaitResponse) {
idx = this.responseId++;
this.responseQueue.set(idx, call);
}
this.send({
idx,
child: call.child,
type: call.type,
location: call.location,
handle: call.handle,
method: call.method,
args: call.args,
awaitResponse: call.awaitResponse,
});
}
processQueue(): void {
if (!this.callQueue.length) {
return;
}
if (this.responseQueue.size < this.maxConcurrentCalls) {
this.sendRequest(this.callQueue.shift());
}
}
handleEnd(): void {
this.loggerDisposable.dispose();
}
createReverseHandle(fn: (...args: Array<any>) => mixed): Handle {
let handle = new Handle({
fn,
childId: this.childId,
});
this.handles.set(handle.id, handle);
return handle;
}
}