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Preparing dev environment for Rails app


(Oscar) #1

Hello!

I’m planning on making my 1st dev environment for Rails app.
I’ll be using mysql as DB.

When using docker, is it a good practice to have separate containers for an app and mysql ?
So, when I’ll docker in production, my understanding I can just replace a docker container for an app with the newer content as a deployment, while keeping mysql container untouched… Is that correct idea?

Let me know if there’s anything missing.
Maybe I will need to separate web server to a different container as well?
I don’t want to re-invent the wheel. :smile:

Thanks.


(Jeff Anderson) #2

It is indeed best practice to keep processes in their own containers. This allows you to do upgrades for one type of service without affecting others as you mentioned.

For a simple web application setup, I generally prefer to have three services: db, app, load_balancer.

Generally, I’d have one load balancer container that reverse proxies to one or more app containers. Each app container would access the db.

Cheers!


(Oscar) #3

Thank you, Jeff!

My understanding is 1 service = 1 container.
Maybe I’m mistaken and we have more than 1 services per 1 container, but it maybe a good practice to have 1 service = 1 container?

And service = process, correct?


(Jeff Anderson) #4

Yes, in my example I am suggesting that one service is one container.

It is certainly possible to put more than one service into a single container. A common approach is to run something like supervisord in the container, and define multiple supervisord services that all get launched.

Generally speaking one service is a single process. There are some cases where a service might launch multiple subprocesses. Apache’s workers, or postfix’s various processses are examples of this.

Some more information on general deploy design can be found at http://12factor.net/. Docker was designed with many of the 12 factor principles and concepts, so it works really well together.

Cheers!


(Oscar) #5

Thanks, Jeff.

I see many new information, which is very helpful. :thumbsup:

Thanks a lot!


(Oscar) #6

Where can I read more about load balancer (including implementation) you’ve mentioned?


(Jeff Anderson) #7

Usually, I’ll fire up an nginx instance to act as a load balancer. It will then use its proxy_pass feature to route requests to the backend application server(s)