and this breaks support for unix socket.

The problem is that once you called DockerCmdExecFactoryImpl.init() once with a configuration containing uri : unix:///var/run/docker.sock , you can't reuse the configuration for a second DockerCmdExecFactoryImpl instance, because the new value set into DockerClientConfig is not supported but init() method.

The obvious fix is to prevent configuration from being modified.

I'll propose a PR soon.