Problem with getting IP from host

[synergiator]

Hi, Dustin,

first of all, thank you for creating and publishing this software!

I have a question regarding a problem I have seen recently. Sometimes, it seems that the driver does not get the IP address of a remote VM properly, or there is some other error.

The following function should do that and in most cases it works well:

// GetURL returns a Docker compatible host URL for connecting to this host
// e.g. tcp://1.2.3.4:2376
func (d *Driver) GetURL() (string, error) {
	ip, err := d.GetIP()
	if err != nil {
		return "", err
	}
	return fmt.Sprintf("tcp://%s:%d", ip, dockerPort), nil
}

But then, sometimes the docker-machine ls would output the following:

NAME         ACTIVE       DRIVER       STATE     URL               SWARM   DOCKER        ERRORS
host-name     -          cloudstack    Running   tcp://:2376                Unknown     Unable to query docker version: Cannot connect to the docker engine endpoint

It looks like the IP is empty and this is not being checked. That is the URL is considered to be tcp://:2376. Do you have any idea why could this happen?

Possibly, the call is put to the API very early, and the program would never refresh this information? Because I am able to login per SSH to the host-name using its IP.

The problem appears for all machines if we try to deploy batches larges than 4 instances. Possibly, this leads to longer IP association times which needs to be tracked by the driver I suppose.

Additional side question - how do I know whether the driver would pick the private or public IP?