CODEWITHSUNDEEP
dockerdockerfile
Valeriy Solovyov
Valeriy Solovyov

Reputation: 5648

How to deal with files of web applications in docker?

How do you guys deal with files of web applications for your docker containers? We are using same application for >400 customers. It's the same application with enabled/disabled modules (there are extra files).

I am currently using this approach: build the images, e.g. for Mysql, nginx+php, and then start the container with specific prepared application folder: 

docker create -v /dbdata --name dbstore x/mysql /bin/true
docker run -d --volumes-from dbstore --name db1 x/mysql
docker run -d -P --name web --link db1:db1 -v /webapp:/opt/webapp x/webapp php-start index.php

IMHO, it's a space overusing. I think it's a little bit complex to create >100 tags(revisions) of a webapp docker data container. Please advice how to manage this problem?

Upvotes: 0

Views: 486

Answers (2)

L0j1k
L0j1k

Reputation: 12645

First, recent versions of Docker let you create and use named volumes. This means that "data-only containers" are antiquated and no longer necessary, and in fact are considered an anti-pattern these days. It's pretty straightforward to create and use a named volume:

docker volume create --name=foo
docker run -d -v "foo:/dbdata" --name "db1" x/mysql

You can view your volumes with:

docker volume ls

As far as your main question, you could take advantage of Docker's union filesystem (which could also more simply be called a "shared layer") design. What this means is that if you create two containers from the ubuntu image (e.g. docker run -d --name=one ubuntu and docker run -d --name=two ubuntu), both of those containers are going to use the same filesystem objects in the base ubuntu image. So for example the /etc/passwd file in both of those containers point to the same /etc/passwd data stored on disk. This is part of what is meant by the term "union filesystem" in the context of Docker.

So just take this knowledge a step further and "bake" those modules into your base image for use by all of the containers for your different customers. That just means creating your own image from a Dockerfile which uses FROM wordpress:latest at the top. Continuing with the WordPress example, and if you wanted to make a bunch of WP plugins available, you could just store them in /var/www/html/wp-plugins (or whatever) and only enable certain ones in your configuration. Since they're baked into the image you have created (and used the same image to create all of your different containers), all of those module files point to the same exact data stored on disk, via the union filesystem. Of course, if someone changes the code in one of their modules, for example, the individual container's image will store the changes in its own image layer, but the base files will all be from the same data, not taking up any extra space. Of course, you can substitute in whichever CMS you're using.

Now, where I work, I've recently created a Docker-based hosting system for people to use. The issue is that we wanted each and every customer to have their own copy of the CMS filesystem. Even though the union filesystem means that changes to the base image would be stored in their own image layers, that wasn't good enough for the guy that signs my paycheck. They wanted each customer to have their own EBS volume with their own copy of the CMS filesystem on it. So in that situation, where you want each and every customer to have their own volume (for example in order to transport them for backup, or move to a new host, etc), then you won't be able to get around the issue of using extra storage for those files.

Upvotes: 2

Norbert
Norbert

Reputation: 6084

It depends:

If the files are static and you want to be able to move the container around easily, then I keep the files in the container by just copying them into the web location as single directory.

If you have a reliable external location, and you change the files more regular (for example by using some kind of CMS), you could just run an apache or a nginx container and mount the volume

Upvotes: 1

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