How to know when all cluster workers are up?

Question

I am looking to bootstrap a node cluster with a start and stop methods.

I wanted to write something similar to:

myCluster.start().then(()=>{
    return myCluster.stop().then(()=>{console.log('smooth stop! nice.')});
}).catch(err=>{console.log('something went wrong')});

How can i exactly tell when all my workers are running?

PS: It doesn't have to be with promises.

Answer 1

I managed to engineer a solution by sending a message from a worker to the master as soon as the worker is listening:

private sendMaster(pid: number, msg: ClusterMessage) {
    process.send({ pid, msg });
}

 self.server.listen(self.options.port, () => {
       self.sendMaster(process.pid, ClusterMessage.WORKER_LISTENING);
       resolve();
    }).on('error', () => {
       logError('Failed to start the server on port %O', self.options.port);
       reject();
});

And in the master code i would grab the messages like this:

cluster.on('message', (worker, data) => {
    logInfo('Process %O listening on port %O', data.pid, self.options.port);
    self.startedWorkersCount++;
    if (self.startedWorkersCount === self.options.workers) {
       logInfo('Server ready');
       resolve(self.startedWorkersCount);
    }
 });

You can check my code with more detail here