lib/internal/worker.js

'use strict';

const EventEmitter = require('events');
const assert = require('internal/assert');
const path = require('path');

const {
  ERR_WORKER_PATH,
  ERR_WORKER_UNSERIALIZABLE_ERROR,
  ERR_WORKER_UNSUPPORTED_EXTENSION,
  ERR_WORKER_INVALID_EXEC_ARGV,
  ERR_INVALID_ARG_TYPE,
} = require('internal/errors').codes;
const { validateString } = require('internal/validators');
const { getOptionValue } = require('internal/options');

const {
  drainMessagePort,
  MessageChannel,
  messageTypes,
  kPort,
  kIncrementsPortRef,
  kWaitingStreams,
  kStdioWantsMoreDataCallback,
  setupPortReferencing,
  ReadableWorkerStdio,
  WritableWorkerStdio,
} = require('internal/worker/io');
const { deserializeError } = require('internal/error-serdes');
const { pathToFileURL } = require('url');

const {
  ownsProcessState,
  isMainThread,
  threadId,
  Worker: WorkerImpl,
} = internalBinding('worker');

const kHandle = Symbol('kHandle');
const kPublicPort = Symbol('kPublicPort');
const kDispose = Symbol('kDispose');
const kOnExit = Symbol('kOnExit');
const kOnMessage = Symbol('kOnMessage');
const kOnCouldNotSerializeErr = Symbol('kOnCouldNotSerializeErr');
const kOnErrorMessage = Symbol('kOnErrorMessage');
const kParentSideStdio = Symbol('kParentSideStdio');

let debuglog;
function debug(...args) {
  if (!debuglog) {
    debuglog = require('internal/util/debuglog').debuglog('worker');
  }
  debuglog(...args);
}

class Worker extends EventEmitter {
  constructor(filename, options = {}) {
    super();
    debug(`[${threadId}] create new worker`, filename, options);
    validateString(filename, 'filename');
    if (options.execArgv && !Array.isArray(options.execArgv)) {
      throw new ERR_INVALID_ARG_TYPE('options.execArgv',
                                     'array',
                                     options.execArgv);
    }
    if (!options.eval) {
      if (!path.isAbsolute(filename) &&
          !filename.startsWith('./') &&
          !filename.startsWith('../') &&
          !filename.startsWith('.' + path.sep) &&
          !filename.startsWith('..' + path.sep)) {
        throw new ERR_WORKER_PATH(filename);
      }
      filename = path.resolve(filename);

      const ext = path.extname(filename);
      if (ext !== '.js' && ext !== '.mjs') {
        throw new ERR_WORKER_UNSUPPORTED_EXTENSION(ext);
      }
    }

    const url = options.eval ? null : pathToFileURL(filename);
    // Set up the C++ handle for the worker, as well as some internal wiring.
    this[kHandle] = new WorkerImpl(url, options.execArgv);
    if (this[kHandle].invalidExecArgv) {
      throw new ERR_WORKER_INVALID_EXEC_ARGV(this[kHandle].invalidExecArgv);
    }
    this[kHandle].onexit = (code) => this[kOnExit](code);
    this[kPort] = this[kHandle].messagePort;
    this[kPort].on('message', (data) => this[kOnMessage](data));
    this[kPort].start();
    this[kPort].unref();
    this[kPort][kWaitingStreams] = 0;
    debug(`[${threadId}] created Worker with ID ${this.threadId}`);

    let stdin = null;
    if (options.stdin)
      stdin = new WritableWorkerStdio(this[kPort], 'stdin');
    const stdout = new ReadableWorkerStdio(this[kPort], 'stdout');
    if (!options.stdout) {
      stdout[kIncrementsPortRef] = false;
      pipeWithoutWarning(stdout, process.stdout);
    }
    const stderr = new ReadableWorkerStdio(this[kPort], 'stderr');
    if (!options.stderr) {
      stderr[kIncrementsPortRef] = false;
      pipeWithoutWarning(stderr, process.stderr);
    }

    this[kParentSideStdio] = { stdin, stdout, stderr };

    const { port1, port2 } = new MessageChannel();
    this[kPublicPort] = port1;
    this[kPublicPort].on('message', (message) => this.emit('message', message));
    setupPortReferencing(this[kPublicPort], this, 'message');
    this[kPort].postMessage({
      type: messageTypes.LOAD_SCRIPT,
      filename,
      doEval: !!options.eval,
      workerData: options.workerData,
      publicPort: port2,
      manifestSrc: getOptionValue('--experimental-policy') ?
        require('internal/process/policy').src :
        null,
      hasStdin: !!options.stdin
    }, [port2]);
    // Actually start the new thread now that everything is in place.
    this[kHandle].startThread();
  }

  [kOnExit](code) {
    debug(`[${threadId}] hears end event for Worker ${this.threadId}`);
    drainMessagePort(this[kPublicPort]);
    drainMessagePort(this[kPort]);
    this[kDispose]();
    this.emit('exit', code);
    this.removeAllListeners();
  }

  [kOnCouldNotSerializeErr]() {
    this.emit('error', new ERR_WORKER_UNSERIALIZABLE_ERROR());
  }

  [kOnErrorMessage](serialized) {
    // This is what is called for uncaught exceptions.
    const error = deserializeError(serialized);
    this.emit('error', error);
  }

  [kOnMessage](message) {
    switch (message.type) {
      case messageTypes.UP_AND_RUNNING:
        return this.emit('online');
      case messageTypes.COULD_NOT_SERIALIZE_ERROR:
        return this[kOnCouldNotSerializeErr]();
      case messageTypes.ERROR_MESSAGE:
        return this[kOnErrorMessage](message.error);
      case messageTypes.STDIO_PAYLOAD:
      {
        const { stream, chunk, encoding } = message;
        return this[kParentSideStdio][stream].push(chunk, encoding);
      }
      case messageTypes.STDIO_WANTS_MORE_DATA:
      {
        const { stream } = message;
        return this[kParentSideStdio][stream][kStdioWantsMoreDataCallback]();
      }
    }

    assert.fail(`Unknown worker message type ${message.type}`);
  }

  [kDispose]() {
    this[kHandle].onexit = null;
    this[kHandle] = null;
    this[kPort] = null;
    this[kPublicPort] = null;

    const { stdout, stderr } = this[kParentSideStdio];

    if (!stdout._readableState.ended) {
      debug(`[${threadId}] explicitly closes stdout for ${this.threadId}`);
      stdout.push(null);
    }
    if (!stderr._readableState.ended) {
      debug(`[${threadId}] explicitly closes stderr for ${this.threadId}`);
      stderr.push(null);
    }
  }

  postMessage(...args) {
    if (this[kPublicPort] === null) return;

    this[kPublicPort].postMessage(...args);
  }

  terminate(callback) {
    if (this[kHandle] === null) return;

    debug(`[${threadId}] terminates Worker with ID ${this.threadId}`);

    if (typeof callback !== 'undefined')
      this.once('exit', (exitCode) => callback(null, exitCode));

    this[kHandle].stopThread();
  }

  ref() {
    if (this[kHandle] === null) return;

    this[kHandle].ref();
    this[kPublicPort].ref();
  }

  unref() {
    if (this[kHandle] === null) return;

    this[kHandle].unref();
    this[kPublicPort].unref();
  }

  get threadId() {
    if (this[kHandle] === null) return -1;

    return this[kHandle].threadId;
  }

  get stdin() {
    return this[kParentSideStdio].stdin;
  }

  get stdout() {
    return this[kParentSideStdio].stdout;
  }

  get stderr() {
    return this[kParentSideStdio].stderr;
  }
}

function pipeWithoutWarning(source, dest) {
  const sourceMaxListeners = source._maxListeners;
  const destMaxListeners = dest._maxListeners;
  source.setMaxListeners(Infinity);
  dest.setMaxListeners(Infinity);

  source.pipe(dest);

  source._maxListeners = sourceMaxListeners;
  dest._maxListeners = destMaxListeners;
}

module.exports = {
  ownsProcessState,
  isMainThread,
  threadId,
  Worker,
};