Adding dependencies to a Docker container

So let’s suppose that you’re me a few weeks ago, and that you find and follow havlev’s guide here. Getting the docker running is quite easy, you just need to set up Docker, and then find the line in the tutorial that starts with docker run…. You’ll get Shiny running with its hello world app. Now, how can you add more packages, either to the base Debian image, or R packages? For this part, I followed this guide. The idea is to “log in” to the console of the base Debian distro that is running from the container. First, find the ID of the container by typing the following command in the terminal:

docker ps

You should see something like this:

ubuntu@ubuntu:~$ docker ps
CONTAINER ID        IMAGE                                COMMAND                  CREATED              STATUS              PORTS                    NAMES
69420blazeit        brodriguesco/shiny_1_5:firstcommit   "/etc/shiny-server/i…"   About a minute ago   Up About a minute   0.0.0.0:3838->3838/tcp   rpi-shiny-server

now with the ID in hand, you can start any command line program from your Docker container, for instance bash:

docker exec -it 69420blazeit bash

You’ll be “logged in” as root:

root@69420blazeit:/# 

and from there, you can install Debian packages. The following two packages are necessary to install many R packages from source, so I recommend you install them:

root@69420blazeit:/# apt-get install libssl-dev libxml2-dev

Once these Debian packages are installed, you can start R by simply typing R in the same console, and install whatever packages your Shiny apps will need. In my case, I installed {golem} and several others, but this will be the subject of another blog post. We’re almost done with that; we now need to save the changes because if you restart the container, you’ll lose all these changes. To save these changes, let’s run the following command, but in a new terminal on your Raspberry Pi (on the “local” Ubuntu, not the Debian running in the container):

ubuntu@ubuntu:~$ docker commit -m "added some dependencies" 69420blazeit shiny_with_deps

So now you could run this container with the command from above, by replacing the adequate parts:

docker run -d -p 3838:3838 -v shiny-apps:/srv/shiny-server/ -v shiny-logs:/var/log/ -v shiny-conf:/etc/shiny-server/ --name rpi-shiny-server shiny_with_depsshiny_with_deps

Using your Shiny server

Ok so now that the server is running, you can you deploy apps on it? Remember the folders that we created at the beginning of the blog post (or that you created if you followed havlev’s guide)? This is where you’ll drop your apps, the usual way. You create a folder there, and simply put the ui.R and server.R files in here, and that it. These folders can be found in your $HOME directory, and they are accessible to your docker container as well. Once you dropped one or two apps, you’ll be able to access them on a link similar as this one:

http://192.168.178.55:3838/hello/

where 192.168.178.55 is the local IP address of the Raspberry Pi, 3838 is the port the server is listening to, and /hello/ is the name of the subfolder contained in the ~/shiny-server/apps folder that you created before. What is left doing is making your Raspberry Pi a proper server that can be accessed from the internet. For this, you’ll need to ask your ISP for a dynamic IP address. Generally, you’ll have to pay some money for it; in my case, I’m paying 2€ a month. This address can then be used to access your Raspberry Pi from the internet. The problem, is that being dynamic, the address changes every time you restart your server. To solve this issue, you can use a free dynamic DNS. I use duckdns. This will allow you to have domain that you can share with the world. What’s nice is that if you follow their guide the redirection to the dynamic IP address will happen seamlessly every time it changes, so no need to think about it and do it manually.

Finally, you’ll also have to open up port 3838 on your router. The procedure changes from router to router, but you should be able to find the instructions for your router quite easily. If not, you should also be able to get help from your ISP.

The end result is that you’ll have your own Shiny server running off a Raspberry Pi, and accessible over the internet! You’ll be able to deploy as many apps as you want, but of course, don’t forget that you’re running all this on a Raspberry Pi. While these machines have become quite powerful over the years, they won’t be powerful enough if you’re running some heavy duty apps with hundreds of concurrent users.

In my next blog post, I’ll walk you through the development of a Shiny app using the {golem} package, which you can find here.

Hope you enjoyed! If you found this blog post useful, you might want to follow me on twitter for blog post updates and buy me an espresso or paypal.me, or buy my ebook on Leanpub.

Buy me an Espresso