Multiple docker deamon leads to swarm problem

[silgon]

This is somehow a continuation of this answer about multiple docker deamons.

They use the following script to create the second docker deamon:

#!/bin/sh
## name: altdocker.sh
set -e -x

: ${bridge=altdocker}
: ${base=$HOME/$bridge}

# Set up bridge network:
if ! ip link show $bridge > /dev/null 2>&1
then
   sudo ip link add name $bridge type bridge
   sudo ip addr add ${net:-"10.20.30.1/24"} dev $bridge
   sudo ip link set dev $bridge up
fi

sudo dockerd \
  --bridge=$bridge \
  --data-root=$base.data \
  --exec-root=$base.exec \
  --host=unix://$base.socket \
  --pidfile=$base.pid

Now, I set my DOCKER_HOST to the unix socket that was created. I initialize a docker swarm with docker swarm init with absolutely no problem. However, once I create a stack with docker stack deploy -c myfile.yaml I have to problems:

• DNS resolution doesn't work (a service cannot call another by hostname, however with the container ip I'm able to ping)
• Connection to the internet is really slow, compared to the connection inside the containers of the default docker deamon.

Note: I created a stackoverflow question, however I realized that it might be better here. Anyway, here is the link to the question.

[cpuguy83]

You also will have issues with iptables, swarm socket addresses... honestly you should not run two dockerd's in the same host unless they are isolated by containers.

[silgon]

The thing is in my case, I need one swarm configuration which is connected to another computer and another to be isolated in local for development. Another use-case is for people who want several isolated docker environments in a single computer, let's say one dockerd for every user, thus they can have isolated configurations.

Looking a bit more in depth, I saw in the documentation the configuration that should be enable in order to use swarm mode:

• Port 7946 TCP/UDP for container network discovery.
• Port 4789 UDP for the container ingress network.

I realized because I saw an error message given by dockerd:

 ERRO[2019-05-21T14:46:02.807800662+02:00] error in agentInit: failed to create memberlist: Could not set up network transport: failed to obtain an address: Failed to start TCP listener on "0.0.0.0" port 7946: listen tcp 0.0.0.0:7946: bind: address already in use 

Is there a way to change these ports?

[thaJeztah]

Let me close this ticket for now, as it looks like it went stale.