I have a golang web application associated with MySQL database. I need to deploy that web application in number of servers provided by different vendors. So I am going to used docker images to deploy this web app. The thing I need to know is, it is okay to keep Mysql server on same docker image or should I make a separate docker image to deploy MySQL on those servers.
A rule of thumb with Docker which you should follow is "One application, one container" It's always the best practice to have separate containers for different parts of your application. The main reason is that down the line if you want to replace MySQL with some NoSQL database, you could simply kill the container and spin up a new one and not worry about it affecting your golang application
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I am migrating an application from openshift 2 such consists of a Java(jetty) webserver and a mongo database.
Both the webserver and mongo need access to persistent storage, as well as the server accessing the database.
As the volume available to me can't (I believe) be accessed by two pods my current goal is to include both the server and dB into the same pod as separate containers.
I have tried copying the mongo container into the deploy config for the server but I just get an error saying the config is invalid with no description of why.
Is this an approach that could work and how can I find out why it isn't?
It is possible to do it if you really needed to, but not normally recommended for production systems.
In doing it, you are limited to a single replica and cannot scale your application, also, you can't use Rolling deployment strategy and must use Recreate.
For some examples of templates which deploy a database with front end together in same pod which you might adapt, see the 'testing' variants of the templates at:
https://github.com/openshift-evangelists/wordpress-quickstart/tree/master/templates
For those templates the build of the application image was done as separate manual step and they were just handling the deployment, so you will need to incorporate the build configuration into them yourself after you have copied and modified them for your own purposes.
UPDATE 1
Those templates do now include build configurations as have been tweaking the way they work.
We are using Docker Images for Spring Boot Rest Services. the current setup is working fine in Production. We want to use the similar setup in Development Environment. The spring boot image needs to connect to the database. At this point we have couple of options:
Have a centralized database server and have all the docker images from each development machine to connect to it.
Create a separate database image and have the developers run it along with the Spring boot image in the same Dev Machine.
Option #1 is easier to implement but if there is a change in the database, it may impact the whole development community in the organization, Option #2 mitigates that risk but it creates the problem of DataSync i.e when someone starts both these images, how to make sure it has all the required data.
I am wondering if there is any other option I need to consider or given these two options, which makes sense?
I went with option #2, it helps to provide isolated work environment.
I have several questions regarding Docker.
First my project:
I have a blog on a shared host and want to move it to the cloud to have all the server sides in my hands and to have the possibility to scale my server on my needs.
My first intend was to setup a nice ubuntu 14 lts as a server with nginx, php 7 and mysql. But I think it's not that easy to transfer such a server to another cloud i.e. from gce to aws. I then thought about using docker, as a friend told me how easy it is to setup containers and how easy it is to move them from one server to another.
I then read a lot about docker but stumbled upon a few things I wondered about.
In my understanding docker runs just services like php, mysql or similar, but doesn't hold data, right?
Where would I store all the data like database, nginx.conf, php.ini and all the Files I want to serve with nginx (ie. /var/www/)?
Are they stored on the host system? If yes, it would not be easier to move a docker setup then move a whole server, no?
Do I really have an advantage of using Docker to serve a Wordpress Blog or another Website using MySQL and so on?
Thanks in advance
Your data is either stored on the host machine or you data is attached to the docker containers remotely (using a network-attached block device).
When you store your data on the host machine, you have a number of options.
The data can be 'inside' one of your containers (e.g. your mysql databases live inside your mysql container).
You can mount one or more directories from your host machine inside your containers. So then the data lives on your host.
You can create Docker volumes or Docker volume containers that are used to store your data. These volumes or volume containers are mounted inside the container with your application. The data then lives in directories managed by Docker.
For details of these options, see dockervolumes
The last option is that you mount remote storage to your docker containers. Flocker is one of the options you have for this.
At my work I've set up a host (i.e. server) that runs a number of services in docker containers. The data for each of these services 'lives' in a Docker data volume container.
This way, the data and the services are completely separated. That allows me to start, stop, upgrade and delete the containers that are running my services without affecting the data.
I have also made separate Docker containers that are started by cron and these back up the data from the data volume containers.
For mysql, the backup container connects to the mysql container and executes mysqldump remotely.
I can also run the (same) containers that are running my services on my development machine, using the data that I backed up from the production server.
This is useful, for instance, to test upgrading mysql from 5.6 to 5.7.
I'm planning to migrate my application stack to Docker. Let me describe the services I'm currently using:
HAProxy, which is used for SSL termination on all service's connections (HTTP and raw TCP connections), and forwards traffic to the services below.
Nginx, which serves static files, like updates and some information pages.
Node.js, which runs the main applications.
MySQL (MariaDB), the database used and shared by all the applications.
My question is about the database.
What's the proper way of running MariaDB in this case?
Install and run it inside my container, along with the other services?
Run the official image in a separate container, and link my container to it with the --link option of Docker's run command?
Does the first option have any disadvantage?
TeamSpeak docker container uses the second option and that's what made me question myself about the correct way of running the database in my case, but I particularly feel more inclined to package all the services inside my own image.
Docker Philosophy: Split your application into microservices and use a container for each microservice.
In your case, I recommend a MariaDB container, Using official (Library) Image gives you easier update management, but feel free to use your custom image.
An HAProxy Container, A nginx container and a nodejs container.
This way you divided your application into microservices, and you can upgrade, manage and troubleshoot them easier in an isolated environment.
If you are thinking about delivering your application to end users via docker, a simple docker-compose file will do the trick for easy launching the required containers.
Wordpress is running inside a Docker container on hostA and MySQL is running inside a Docker container on hostB. Is it possible to link these two containers to communicate to each other? Is this even possible to do something like this?
Any help on this is much appreciated as am pretty new to Docker
I can not answer you question but there is a part in the documentation about this:
https://docs.docker.com/engine/userguide/networking/default_network/container-communication/
You will find a section called: Communication between containers
Yes this is possible with docker overlay network.
The setup is not as easy as setting up a link or private network on the same host.
You will have to configure a key value store to get this working.
Here is the relevant docker documentation.
An overlay network:
https://docs.docker.com/engine/userguide/networking/dockernetworks/#an-overlay-network
Here are the steps for setup
https://docs.docker.com/engine/userguide/networking/get-started-overlay/
In my opinion, its not bad to isolate the app and database containers and connect outside the docker network. If you end up adding the key/value store like consul, you can always leverage the service discovery that comes along with it to dynamically discover the services.
I would go for https://github.com/weaveworks/weave.
Weave Net creates a virtual network that connects Docker containers across multiple hosts and enables their automatic discovery.
It might be overkill for your usecase. But it would be very helpful if you want to move the containers around in the future.