Docker As Application Registry

Docker As Application Registry

Docker is great and solves a lot of problems with deployments. It taught VMs to share the resources, like how VMs taught hardware to share resources! Along with production, I have found that docker can work great as an application registry in a local development environment.
By applications I mean software that you install on your OS and launch them with shortcuts and they continue to live and retain state till you uninstall them; not exactly what containers are designed for but can work as. Something like snap or flatpak but with docker and for servers as well, not just for UI apps.

One advantage this has over using standard installers (like apt-get) is you are at complete liberty to start and stop the background processes, like mysql. If you installed mysql this way, you do not need to go and disable the autostart for it, it just does not matter! Similarly for your SonarQube server, you do not need to install it as a daemon, neither do you need to remember where you downloaded it to be able to restart it. Another advantage is most of such applications do have official docker images, it is the intended way to use them now!

One disadvantage of this method is that you always need to address them with their IP, you will not be able to bind them on host network then. But in my view, it is always better to have a dedicated IP, it emulates production scenario better and does not clutter your local machine ports.
So for apps what you need is containers to live long, be able to identify them with name, start and stop them easily and have a dedicated, static address to be able to reach to them. Most of these things are easy, except for a static IP. But once you create a network, you are set. That is it, it is that easy! Create a virtual network, and start your dockers with a name and static IP in that network. Simple!

To create a network:
docker network create -d bridge --subnet="172.30.0.0/24" --gateway="172.30.0.100" --ip-range="172.30.0.0/24" permanet

Now any app you need, just specify this network and a static IP of your choice; like this:
docker run --name mysql-server --network="permanet" --ip="172.30.0.1" -e MYSQL_ROOT_PASSWORD=my-secret-pw -d mysql/mysql-server:5.7

More complex containers can be created like this:
docker run -it --name gocd-server --network="permanet" --ip="172.30.0.5" -v /yourhome/docker-volumes/gocd/godata:/godata -v /yourhome/docker-volumes/gocd/home:/home/go gocd/gocd-server

I keep a dedicated directory in my home for docker volumes, so I can back it up and use them as is when I change machines or OS. I also have a script where I add all the containers I need, so it is just a matter of copying the volume directory and running the script to create identical setups. Then even your .desktop files work as is!

Here is an interesting setup script for Jenkins (gist), it externalises all data directories from Jenkins, including the plugins and users and mounts your local m2 repository inside Jenkins so as to avoid downloading the libs again :
docker run -it --name jenkins --network="permanet" --ip="172.30.0.6" \
  -v /yourhome/.m2:/var/jenkins_home/.m2 \
  -v /yourhome/docker-volumes/jenkins/workspace:/var/jenkins_home/workspace \
  -v /yourhome/docker-volumes/jenkins/jobs:/var/jenkins_home/jobs \
  -v /yourhome/docker-volumes/jenkins/plugins:/var/jenkins_home/plugins \
  -v /yourhome/docker-volumes/jenkins/users:/var/jenkins_home/users \
jenkins:2.32.3-alpine

You can create as many such networks as you wish for logical separation of groups of such apps; in my case this is the third network (172.30 for that reason), since first two were taken up by some compose scripts.

A list of few such containers I use: mysql (different versions), SonarQube, hystrix-dashboard, zipkin, swagger-ui, a redis-cluster for local use, gocd-server, Jenkins, portainer, postgres, pgadmin etc. I even have a couple Windows software running on wine in such containers, we shall talk about it some day.

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