node/test/parallel/test-cluster-eaccess.js

// Copyright Joyent, Inc. and other Node contributors.
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'use strict';
const common = require('../common');

// Test that errors propagated from cluster workers are properly
// received in their master. Creates an EADDRINUSE condition by forking
// a process in child cluster and propagates the error to the master.

const assert = require('assert');
const cluster = require('cluster');
const fork = require('child_process').fork;
const net = require('net');

if (cluster.isMaster && process.argv.length !== 3) {
  // cluster.isMaster
  common.refreshTmpDir();
  const PIPE_NAME = common.PIPE;
  const worker = cluster.fork({ PIPE_NAME });

  // makes sure master is able to fork the worker
  cluster.on('fork', common.mustCall());

  // makes sure the worker is ready
  worker.on('online', common.mustCall());

  worker.on('message', common.mustCall(function(err) {
    // disconnect first, so that we will not leave zombies
    worker.disconnect();
    assert.strictEqual('EADDRINUSE', err.code);
  }));
} else if (process.argv.length !== 3) {
  // cluster.worker
  const PIPE_NAME = process.env.PIPE_NAME;
  const cp = fork(__filename, [PIPE_NAME], { stdio: 'inherit' });

  // message from the child indicates it's ready and listening
  cp.on('message', common.mustCall(function() {
    const server = net.createServer().listen(PIPE_NAME, function() {
      // message child process so that it can exit
      cp.send('end');
      // inform master about the unexpected situation
      process.send('PIPE should have been in use.');
    });

    server.on('error', function(err) {
      // message to child process tells it to exit
      cp.send('end');
      // propagate error to parent
      process.send(err);
    });
  }));
} else if (process.argv.length === 3) {
  // child process (of cluster.worker)
  const PIPE_NAME = process.argv[2];

  const server = net.createServer().listen(PIPE_NAME, common.mustCall(() => {
    process.send('listening');
  }));
  process.once('message', common.mustCall(() => server.close()));
} else {
  assert.fail('Impossible state');
}