Docker containers standalone versus using docker-compose

Docker Hub
1

Hello,
I have an application where the UI connects to the backend on udp port. When i run the backend process in a standalone docker container, the UI connects fine with the backend. However, if i run the same backend container using docker-compose, UI doesn’t seem to connect to the backend. when i see standalone the container using docker container ls, i don’t see any ports explicitly exposed but it works. However, i even tried to expose the ports in docker-compose, the container hosted doesn’t show connections. Any idea what could be different between running the container standalone versus with docker compose?

Thank you in advance!

Best Regards
SG

2

Please provide the exact commands you use to start your containers from the cli and your compose file. There must be a configuration difference.

I have yet to encounter a docker run command that is not expressable as a compose file and vice versa. They are just different representations of a “client-frontend” that drive the very same api endpoints of the docker engine.

3

Thanks for the prompt response. My standalone command is:

docker run -d --pid=host --network=host -u $(id -u):$(id -g) --rm test-container

whereas my docker-compose.yaml:

version: '3.7'
services:
  mycontainer:
    image: test-container
    command: test
    restart: unless-stopped
    ports:
      - "1114:1114/udp"

Not sure what difference is causing this:

Thanks in advance for your help!

SG

4

The most obvious differences between your docker run and compose file are:
equivalent of --pid=host missing in compose file
equivalent of --network=host missing in compose file (uses bridge instead and published ports)
equivalent of -u $(id -u):$(id -g) missing in compose file
your comose file has a command, you docke run does not.

Let me take a look at the compose specs and fill the voids. Which is the prefered network approach? host network OR brige + published ports?

update: I reformated your post, now the -u parameter makes sense.

5

Host network is fine. Thank you

6

The compose equivalent of docker run -d --name=mycontainer --pid=host --network=host -u $(id -u):$(id -g) --rm test-container

note: I added --name=mycontainer to reflect the service configuration in the compose file

is this compose file:

version: '2.4'
services:
  mycontainer:
    pid: host
    network: host
    user:  ${UID}:${GID}
    image: test-container

But, you can not run sub-commands in a compose file: so neither its $() or backtick syntax will work. As such the variables must exist in the shell before running docker-compose. Either by exporting them before or by prefixing your docker-compose command with it.

This should work(haven’t tested it though):
UID=$(id -u) GID=$(id -g) docker-compose up -d

7

Small correction: I think you wanted to write “network_mode: host”, not just network which would work in the build section according to the documentation. i don’t know why Docker uses two different names for the same purpose in two different place. I didn’t even know I could use network: host during build until today :smiley: so thanks.

8

good catch! indeed I ment network_mode: host.
Thanks @rimelek

Actualy this one should work without sub-process magic relying on internal bash variables:

version: '2.4'
services:
  mycontainer:
    pid: host
    network_mode: host
    user:  ${UID}:${GROUPS}
    image: test-container
9

Thank you for the prompt help and clarification!!!