Question

I have this utility function which launches a child process. As soon as the child process writes a certain message to stdout, we are supposed to stop listening and fire the callback:

export const launchBrokerInChildProcess = function (opts: any, cb: Function) {

  const host = opts.host || 'localhost';
  const port = opts.port || 8019;
  const detached = Boolean(opts.detached);

  ping.probe(host, port, function (err, available) {

    if (err) {
      return cb(err)
    }

    if (available) {
      log.info(`live-mutex broker/server was already live at ${host}:${port}.`);
      return cb(null, {host, port, alreadyRunning: true});
    }

    log.info(`live-mutex is launching new broker at '${host}:${port}'.`);

    const n = cp.spawn('node', [p], {
      detached,
      env: Object.assign({}, process.env, {
        LIVE_MUTEX_PORT: port
      })
    });

    if (detached) {
      n.unref();
    }

    process.once('exit', function () {
      if (!detached) {
        n.kill('SIGINT');
      }
    });

    n.stderr.setEncoding('utf8');
    n.stdout.setEncoding('utf8');
    n.stderr.pipe(process.stderr);

    let stdout = '';
    n.stdout.on('data', function (d) {

      stdout += String(d);

      if (stdout.match(/live-mutex broker is listening/i)) {

        n.stdout.removeAllListeners();

        if (detached) {
          n.unref();
        }

        console.log(33333);
        cb(null, {
          liveMutexProcess: n,
          host,
          port,
          detached
        });
      }
    });
  });

};

what's happening is that console.log(33333); is being hit over and over and over again. Very strange - does anyone know why that would happen?

The ping.probe() callback is firing only once, I have confirmed that. So I don't know what's happening.

here is the script that gets launched:

import {Broker} from './broker';

const port = parseInt(process.argv[2] || process.env.LIVE_MUTEX_PORT || '6970');

new Broker({port: port}).ensure().then(function () {
  console.log(`live-mutex broker is listening on port ${port}.`);
})
.catch(function (err) {
  console.error(err.stack || err);
});

so that line ('live-mutex broker is listening') should only be logged once, given that it's a promise.

Answer 1

也许其他人使用端口8019，尝试使用其他端口，如3000。

Callback is being fired multiple times and I cannot figure out why

1 个答案: