I have installed and configured a system in EC2s using Ansible. It is 1 EC2 master with a few EC2 workers. Sometimes when I use ansible to update or reinstall configuration, it fails because either some package has been removed from open-source repositories, or the package is updated so not compatible with some other packages. And I learned that using docker-container can resolve these kind of configuration problems.
However, according to what I learned, each docker image will create image of one application (I guess one application means one process). But mine is a system which has airflow master webserver, airflow worker webserver, flower webserver, rabbitmq, airflow celery, several configuration files, etc. how can I create docker images for that? Should I create one docker image for each process? How do I know which linux folder should I go to create each docker image? How do I know which applications/processes I need to create? And how to combine these images to make them work together as a system?
Or maybe in my case I should not use docker image, Instead I should just create an EC2 image?
Use docker-compose.
Compose is a tool for defining and running multi-container Docker applications
https://docs.docker.com/compose/
each docker image will create image of one application (I guess one application means one process)
That is basically correct. You should create one docker-container per application. In theory you can have multiple process per container, but that doesn't matter in this case.
how can I create docker images for that?
In your case you should make one docker-container for airflow master webserver, one for airflow worker webserver, one for flower webserver, etc. And the you use a docker-compose.yml to link them all together.
Should I create one docker image for each process?
generally yes. (It may depend on your exact setup though)
And how to combine these images to make them work together as a system?
docker-compose.
How do I know which linux folder should I go to create each docker image?
I don't understand that question
How do I know which applications/processes I need to create?
You could create a deployment-diagram and then start from there.
Related
I have been working on a project where I have had several docker containers:
Three OSRM routing servers
Nominatim server
Container where the webpage code is with all the needed dependencies
So, now I want to prepare a version that a user could download and run. What is the best practice to do such a thing?
Firstly, I thought maybe to join everything into one container, but I have read that it is not recommended to have several processes in one place. Secondly, I thought about wrapping up everything into a VM, but that is not really a "program" that a user can launch. And my third idea was to maybe, write a script, that would download each container from Docker Hub separately and launch the webpage. But, I am not sure if that is best practice, or maybe there are some better ideas.
When you need to deploy a full project composed of several containers.
You may use a specialized tool.
A well known for mono-server usage is docker-compose:
Compose is a tool for defining and running multi-container Docker applications
https://docs.docker.com/compose/
You could provide to your users :
docker-compose file
your application docker images (ex: through docker hub).
Regarding clusters/cloud, we talk more about orchestrator like docker swarm, Kubernetes, nomad
Kubernetes's documentation is the following:
https://kubernetes.io/
I have a docker stack deployed with 20+ services which comprise my application. I would like to know that is there a way to update this stack with the latest changes to the software from within one of the containers running as a part of the stack?
Approach i have tried:
In one of the containers for a service, mounted the docker socket and the /usr/bin/docker file and downloaded the latest compose file from the server.
Instantiated a script which downloads the latest images
Initiate a docker stack deploy with the new compose file
Everything works fine this way but if the service which is running this process itself has an update and if that docker stack deploy tries to create this service before any other service in the stack, then the stack update fails.
Any suggestion or alternative approaches for this?
There is no out of the box solution for docker swarm mode (something like watchtower for single docker). I think you already found the best solution for doing this automatically. I would suggest you put the update container (the one that is updating the services) on a ignore list. Then on one of your master nodes, create a cron that updates that one container. I know this is not a prefect solution, but it should work.
The standard way to do this is to build a new Docker image that contains your new application code. Tag it (as in the docker build -t argument) with some unique version, like a source control tag or date stamp. Start a new container with the new application code, then stop and delete the old container.
As a general rule you do not upgrade the software inside a running container. Delete the old container and start a new container with the software and version you want. Also, this is generally managed by an operator, a continuous deployment system, or an orchestration system, not by the container itself. (Mounting the Docker socket into a container is a significant security exposure.)
(Imagine setting up a second copy of your cluster that works exactly the same way as your production cluster, except that it has the software you want to deploy tomorrow. You don't want your production cluster picking that up on its own until you've tested it. This scheme should give you a reproducible deployment setup so that it's easy to start that pre-production cluster, but also give you control over which specific versions are running where.)
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.
Question about Docker best practices/intended use:
I have docker working, and it's cool. I run a PaaS company, and my intent is maybe to use docker to run individual instances of our service for a given user.
So now I have an image that I've created that contains all the stuff for our service... and I can run it. But once I want to set it up for a specific user, theres a set of config files that I will need to modify for each user's instance.
So... the question is: Should that be part of my image filesystem, and hence, I then create a new image (based on my current image, but with their specific config files inside it) for each user?
Or should I put those on the host filesystem in a set of directories, and map the host filesystem config files into the correct running container for each user (hence, having only one image shared among all users)?
Modern PAAS systems favour building an image for each customer, creating versioned copies of both software and configuration. This follows the "Build, release, run" recommendation of the 12 factor app website:
http://12factor.net/
An docker based example is Deis. It uses Heroku build packs to customize the software application environment and the environment settings are also baked into a docker image. At run-time these images are run by chef on each application server.
This approach works well with Docker, because images are easy to build. The challenge I think is managing the docker images, something the docker registry is designed to support.