`docker swarm leave` removes port mapping of standalone containers

Docker Engine Swarm
1

When I do a docker swarm leave, all port mapping from any standalone container is removed. The containers themselves keep running, and I can restart them to recover from the issue. I’d expect standalone containers to stay unaffected by swarm nodes/services in general.

Am I understanding something wrong or Is this a known bug?

I confirmed this issue on Docker 20.0 and 24.0.

2

Sounds like a bug. I have no idea if this is a known bug.

You can raise an issue in the Swarmkit Github project::

1 Like
3

I filed this here: `docker swarm leave` removes port mapping from standalone containers started via docker-compose · Issue #47392 · moby/moby · GitHub

I should add that actually only containers started via docker-compose seem affected. When preparing a test case that uses the docker command line to start a simple nginx, the issue wasn’t reproducible. I could reproduce it on a simple nginx docker-compose.yaml however.

4

I am very interested in this issue, as new Traefik v3 enables local and swarm containers.

I tried to reproduce in a fresh Debian VM, but I don’t see ports removed as in not working anymore.

# Update Debian
sudo apt update
sudo apt -y upgrade

# Install Docker
curl -fsSL https://get.docker.com | sh -

# Run independent Docker container on port 80
docker run -d -p 80:80 --name whoami80 traefik/whoami

# Run independent Docker container on port 8080 with compose
cat << EOF > docker-compose.yml
version: '3'
services:
  whoami8080:
    image: traefik/whoami
    container_name: whoami8080
    ports:
      - 8080:80
EOF
docker compose up -d

# Check independent Docker containers
docker ps
curl http://localhost
curl http://localhost:8080

# Wait 1 minute to get a meaningful uptime 
echo sleep 65
sleep 65

# Init Docker Swarm
docker swarm init

# Wait 10 secs to settle
echo sleep 10
sleep 10

# Remove Swarm
docker swarm leave --force

# Check independent Docker containers
docker ps
curl http://localhost
curl http://localhost:8080

# Wait 10 secs to settle
echo sleep 10
sleep 10

# Check independent Docker containers
docker ps
curl http://localhost
curl http://localhost:8080

It always shows this, before and after swarm:

CONTAINER ID   IMAGE            COMMAND     CREATED              STATUS              PORTS                                   NAMES
b7e41cfb6dc5   traefik/whoami   "/whoami"   About a minute ago   Up About a minute   0.0.0.0:8080->80/tcp, :::8080->80/tcp   whoami8080
dc000729ef56   traefik/whoami   "/whoami"   About a minute ago   Up About a minute   0.0.0.0:80->80/tcp, :::80->80/tcp       whoami80

But I am using Docker v25.

5

I just tried your docker-compose example (not the docker CLI) on Docker version 24.0.5, build 24.0.5-0ubuntu1~22.04.1 and docker-compose version 1.29.2, build unknown – it reproduced the issue.