Is there a way to launch an app on connect so it can stay closed when unused but still have the web access running?

[pugly-tech]

Some apps don't really need to be runnign 24/7, is there a way to set up a container so that you can quit the app and the docker goes into an idle mode with just a login page, and when someone logs in it relaunches the app automatically?

[deimi]

One solution I can think of is putting your own reverse proxy in front of it. E.g. Nginx can execute LUA/shell scripts https://www.baeldung.com/ops/nginx-run-shell-script

You can then write your own script which starts the main application container and also stops the container if there has not been a request for some time.

[jlesage]

Yeah that could be an easier solution than doing something built-in in the baseimage.

Note that there is also the cases of VNC clients. The web is not the only interface.

[deimi]

True that! Don't know VNC and the RFB protocoll enough, but is there no way to connect to a VNC server through a proxy as well?

[pugly-tech]

Is it not possible to set a docker container that basically goes to sleep until it detects an incoming ping through http and/or vnc?

Or even just one where instead of launching the app it launches a button to launch the app, which pops up again when the app is closed

[deimi]

Seems like there exist already tools for this, so you don't need to write your own scripts. Basically they are reverse proxies.

https://github.com/vmorganp/Lazytainer https://github.com/NathanDecou/wakontainer https://sablierapp.dev/

But I don't know if they also are able to handle the case with VNC client connections.

[deimi]

Ok, I tried it now with Lazytainer

version: "3"
services:
  lazytainer:
    container_name: lazytainer
    image: ghcr.io/vmorganp/lazytainer:master
    environment:
      - VERBOSE=true
    ports:
      - 5800:5800
      - 5900:5900
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro
    labels:
      - "lazytainer.group.xterm.sleepMethod=stop"
      - "lazytainer.group.xterm.ports=5800,5900"
      - "lazytainer.group.xterm.inactiveTimeout=30" # 30 seconds
      - "lazytainer.group.xterm.minPacketThreshold=10"
      - "lazytainer.group.xterm.pollRate=5"
  xterm:
    image: docker-xterm
    build:
      dockerfile: Dockerfile
      context: .
    network_mode: service:lazytainer
    restart: unless-stopped
    labels:
      - "lazytainer.group=xterm"
    depends_on:
      - lazytainer

It basically works. I can connect through web and VNC. After the container is stopped, I can wake it up and by connecting. Configuration is a little bit tricky and one has to play around with the settings in order to find a balance between not staying awake all the time and being able to wake it up. What I also have seen is that pause instead of stop works better for a vnc connection in order to wake it up. But with VNC it was most of the time not really realiable to wake it up, but I had to try to cannot multiple times in order to generate enough traffic that lazytrainer detects a enough packets for waking up. It helps to explicitly send tcp packets before trying to connect. E.g. when I add

bash -c 'for run in {1..3}; do dd if=/dev/urandom count=100 bs=100 > /dev/tcp/127.0.0.1/5900 ; done; sleep 5'

as "Before connecting" command in Remmina, it reliable wakes up before establising the VNC connection.