Let's assume scenario I'm using a set of CLI docker run commands for creating a whole environment of containers, networks (bridge type in my case) and connect containers to particular networks.
Everything works well till the moment I want to have only one such environment at a single machine.
But what if I want to have at the same machine a similar environment to the one I've just created but for a different purpose (testing) I'm having an issue of name collisions since I can't crate and start containers and networks with the same name.
So far I tried to start second environment the same way I did with the first but with prefixing all containers and networks names.That worked but had a flaw: in the application that run all requests to URIs were broken since they had a structure
<scheme>://<container-name>:<port-number>
and the application was not able to reach <prefix-container-name>.
What I want to achieve is to have an exact copy of the first environment running on the same machine as the second environment that I could use to perform the application tests etc.
Is there any concept of namespaces or something similar to it in Docker?
A command that I could use before all docker run etc commands I use to create environment and have just two bash scripts that differ only by the namespace command at their beginning?
Can using virtual machine, ie Oracle Virtualbox be the solution to my problem? Create a VM for the second environment? isn't that an overkill, will it add an additional set of troubles?
Perhaps there is a kind of --hostname for docker run command that will allow to access the container from other container by using this name? Unlucky --hostname only gives ability to access the container by this name form the container itself but not from any other. Perhaps there is an option or command that can make an alias, virtual host or whatever magic common name I could put into apps URIs <scheme>://<magic-name>:<port-number> so creating second environment with different containers and networks names will cause no problem as long as that magic-name is available in the environment network
My need for having exact copy of the environment is because of tests I want to run and check if they fail also on dependency level, I think this is quite simple scenario from the continues integration process. Are there any dedicated open source solutions to what I want to achieve? I don't use docker composer but bash script with all docker cli commands to get the whole env up and running.
Thank you for your help.
Is there any concept of namespaces or something similar to it in Docker?
Not really, no (but keep reading).
Can using virtual machine [...] be the solution to my problem? ... Isn't that an overkill, will it add an additional set of troubles?
That's a pretty reasonable solution. That's especially true if you want to further automate the deployment: you should be able to simulate starting up a clean VM and then running your provisioning script on it, then transplant that into your real production environment. Vagrant is a pretty typical tool for trying this out. The biggest issue will be network connectivity to reach the individual VMs, and that's not that big a deal.
Perhaps there is a kind of --hostname for docker run command that will allow to access the container from other container by using this name?
docker run --network-alias is very briefly mentioned in the docker run documentation and has this effect. docker network connect --alias is slightly more documented and affects a container that's already been created.
Are there any dedicated open source solutions to what I want to achieve?
Docker Compose mostly manages this for you, if you want to move off of your existing shell-script solution: it puts a name prefix on all of the networks and volumes it creates, and creates network aliases for each container matching its name in the YAML file. If your host volume mounts are relative to the current directory then that content is fairly isolated too. The one thing you can't easily do is launch each copy of the stack on a separate host port(s), so you have to resolve those conflicts.
Kubernetes has a concept of a namespace which is in fact exactly what you're asking for, but adopting it is a substantial investment and would involve rewriting your deployment sequence even more than Docker Compose would.
Related
I'm new with docker, and have some doubts.
In a dev environment (not server), is better to use just one container, with apache, php and mysql for exemple, and use just a docker and a Dockerfile, or is better to use one container for each service, and use docker-compose to do it?
I have made this here with docker-compose, but I don't know if it is the best way, seems to me unnecessary complexity, but I'm newb.
I have the following situation, I work with magento, and is a common need to have a clear instalation for isolate modules and test, so I want create my magento 2 docker environment, where have just a clear magento and must have some easy way of put my module files inside, for test, and ons shutdown, the environment backs to clear magento 2 instalation, without my files, what is the best way to get this environemnt?
Thanks in advance.
I'd certainly recommend using a docker stack (defined in a docker-compose), and not trying to spin up a whole application stack inside a single container. You should have one service per container generally.
I believe what you are looking for in the second part of your question is a deployment orchestration tool. Docker does not replace deployment orchestration, but you can run shell scripts that do application setup in the Dockerfiles that build the containers you use in your stack.
As for access to files inside your containers, I'd look into docker volumes.
I'm new to Docker. I wanted to create a Dockerfile to start services like RabbitMQ, ftp server and elastic search. But I'm not able to think from where should I start ?
I have asked a similar question here : How should I create a Dockerfile to run more than one services in one instance?
There I got to know, to create different containers : one for rabbitmq, one for ftp server and other for elasticsearch and run them using docker-compose file. There you'll find my created Dockerfile code.
It will be great if someone can help me out with this thing. Thanks!
They are correct. Each container & by extension, each image should be responsible for one concern & that is typically mapped to a single process. So if you need to run more than one thing (or more than one process, generally speaking, not strictly) then you most probably require to build separate images. One of the easiest & recommended ways of creating an image is writing a Dockerfile. This is expected to be an extremely simple process and most of it will be a copy paste of the same commands you would have used to install that component.
One you write the Dockerfile's for each service, you must build them using docker build command, which will result in the images.
When you run an image you get what is known as a container. Think of it roughly like an iso file is the image & the actual vm or running machine is the container.
Now you can use docker-compose to orchestrate how these various containers so they can communicate (or be isolated from) with each other. A docker-compose.yml file is a plain text file in the yaml format that describes the relationship between the different components within the app. Apps can be made up of several services - like webserver, appserver, searchengine, database server, cache engine etc etc. Each of these is a service and runs as a container, but it is also not necessary to run everything as a container. Some can remain running in the traditional way, on VM's or on bare metal servers.
I'll check your other post and add if there is anything needed. But I hope this helps you get started at least.
Is it a good or bad practice to configure docker container with ansible, from within the container, providing ansible command as an entrypoint? Using ansible it would be easier to configure things depending of some lookup conditions. This ansible command would also start the provided service. Is this a good or evil? Another option would be to use shell script, and third one to make all the configuration in Dockerfile (error prone). Last option would be to configure some base container from withing using any method (manual or CM) and commit changes (hard to reproduce). Which is the preferred way to configure containers?
IMO, using ansible would decouple business logic from docker platform, so same service could be easily ran at different virtualization platform or bare metal by just a singe ansible command. But is there drawbacks?
Also, is it endorsed to configure running containers with ansible, or does this violate docker doctrine?
Ansible is generally executed from outside the container but it doesn't have to be, it depends on what you want to achieve. For example Ansible installed locally is often used in small development environments such as on a developers laptop while a seperate server is used for something like a cloud environment where there are multiple systems, containers, etc.
I have just spent a few weeks looking at exactly this problem.
For the same application (based on a tomee and mongo), I have done the following patterns:
Just ansible deploying to one or more VMs
Creating containers which then run ansible scripts inside themselves as you did
Using ansible-container
I did them in that order because it meant going from simple to more complex. I am a product manager and my different customers are at different levels of maturity, so I had the same concerns as you. I wanted a repeatable script which would work both on VMs (or even bare metal), as well as on containerised environments.
The first solution is a good way to learn.
The second solutions works, but it means that your containers are bigger than they should be.
The third solution is better for the following reasons:
It basically forces you to start using roles. If you haven't started using roles, you should.
It effectively decouples the business logic from docker and keeps it in ansible (even more than the second solution)
If you are deploying to VMs, you should be able to use the playbooks from the roles
If you are deploying with docker-compose, you go up to ansible-container push and then supply your customer with a docker-compose file whey they can execute
If you deploying to cloud, ansible-container creates a playbook to pull and run the containers (thought I am still working through this one)
I'm new to Docker and was wondering if it was possible (and a good idea) to develop within a docker container.
I mean create a container, execute bash, install and configure everything I need and start developping inside the container.
The container becomes then my main machine (for CLI related works).
When I'm on the go (or when I buy a new machine), I can just push the container, and pull it on my laptop.
This sort the problem of having to keep and synchronize your dotfile.
I haven't started using docker yet, so is it something realistic or to avoid (spacke disk problem and/or pull/push timing issue).
Yes. It is a good idea, with the correct set-up. You'll be running code as if it was a virtual machine.
The Dockerfile configurations to create a build system is not polished and will not expand shell variables, so pre-installing applications may be a bit tedious. On the other hand after building your own image to create new users and working environment, it won't be necessary to build it again, plus you can mount your own file system with the -v parameter of the run command, so you can have the files you are going to need both in your host and container machine. It's versatile.
> sudo docker run -t -i -v
/home/user_name/Workspace/project:/home/user_name/Workspace/myproject <container-ID>
I'll play the contrarian and say it's a bad idea. I've done work where I've tried to keep a container "long running" and have modified it, but then accidentally lost it or deleted it.
In my opinion containers aren't meant to be long running VMs. They are just meant to be instances of an image. Start it, stop it, kill it, start it again.
As Alex mentioned, it's certainly possible, but in my opinion goes against the "Docker" way.
I'd rather use VirtualBox and Vagrant to create VMs to develop in.
Docker container for development can be very handy. Depending on your stack and preferred IDE you might want to keep the editing part outside, at host, and mount the directory with the sources from host to the container instead, as per Alex's suggestion. If you do so, beware potential performance issue on macos x with boot2docker.
I would not expect much from the workflow with pushing the images to sync between dev environments. IMHO keeping Dockerfiles together with the code and synching by SCM means is more straightforward direction to start with. I also carry supporting Makefiles to build image(s) / run container(s) same place.
I have a hunch that docker could greatly improve my webdev workflow - but I haven't quite managed to wrap my head around how to approach a project adding docker to the stack.
The basic software stack would look like this:
Software
Docker image(s) providing custom LAMP stack
Apache with several modules
MYSQL
PHP
Some CMS, e.g. Silverstripe
GIT
Workflow
I could imagine the workflow to look somewhat like the following:
Development
Write a Dockerfile that defines a LAMP-container meeting the requirements stated above
REQ: The machine should start apache/mysql right after booting
Build the docker image
Copy the files required to run the CMS into e.g. ~/dev/cmsdir
Put ~/dev/cmsdir/ under version control
Run the docker container, and somehow mount ~/dev/cmsdir to /var/www/ on the container
Populate the database
Do work in /dev/cmsdir/
Commit & shut down docker container
Deployment
Set up remote host (e.g. with ansible)
Push container image to remote host
Fetch cmsdir-project via git
Run the docker container, pull in the database and mount cmsdir into /var/www
Now, this looks all quite nice on paper, BUT I am not quite sure whether this would be the right approach at all.
Questions:
While developing locally, how would I get the database to persist between reboots of the container instance? Or would I need to run sql-dump every time before spinning down the container?
Should I have separate container instances for the db and the apache server? Or would it be sufficient to have a single container for above use case?
If using separate containers for database and server, how could I automate spinning them up and down at the same time?
How would I actually mount /dev/cmsdir/ into the containers /var/www/-directory? Should I utilize data-volumes for this?
Did I miss any pitfalls? Anything that could be simplified?
If you need database persistance indepent of your CMS container, you can use one container for MySQL and one container for your CMS. In such case, you can have your MySQL container still running and your can redeploy your CMS as often as you want independently.
For development - the another option is to map mysql data directories from your host/development machine using data volumes. This way you can manage data files for mysql (in docker) using git (on host) and "reload" initial state anytime you want (before starting mysql container).
Yes, I think you should have a separate container for db.
I am using just basic script:
#!/bin/bash
$JOB1 = (docker run ... /usr/sbin/mysqld)
$JOB2 = (docker run ... /usr/sbin/apache2)
echo MySql=$JOB1, Apache=$JOB2
Yes, you can use data-volumes -v switch. I would use this for development. You can use read-only mounting, so no changes will be made to this directory if you want (your app should store data somewhere else anyway).
docker run -v=/home/user/dev/cmsdir:/var/www/cmsdir:ro image /usr/sbin/apache2
Anyway, for final deployment, I would build and image using dockerfile with ADD /home/user/dev/cmsdir /var/www/cmsdir
I don't know :-)
You want to use docker-compose. Follow the tutorial here. Very simple. Seems to tick all your boxes.
https://docs.docker.com/compose/
I understand this post is over a year old at this time, but I have recently asked myself very similar questions and have several great answers to your questions.
You can setup a MySQL docker instance and have data persist on a stateless data container, aka the data container does not need to be actively running
Yes I would recommend having a separate instance for your web server and database. This is the power of Docker.
Check out this repo I have been building. Basically it is as simple as make build & make run and you can have a web server and database container running locally.
You use the -v argument when running the container for the first time, this will link a specific folder on the container to the host running the container.
I think your ideas are great and it is currently possible to achieve all that you are asking.
Here is a turn key solution achieving all of the needs you have listed.
I've put together an easy to use docker compose setup that should match your development workflow requirements.
https://github.com/ehyland/docker-silverstripe-dev
Main Features
Persistent DB
Your choice of HHVM + NGINX or Apache2 + PHP5
Debug and set breakpoints with xDebug
The README.md should be clear enough to get you started.