Deploying Django to DreamHost

Presented at PyYYC, 2014-01-22

You have a Django site that works on your local machine, and you want to run it on the public internet cheaply with a one-line command to immediately push your local changes to the live site.

Here are the steps used to get the tutorial polls Django app in this mercurial repository running on a real web server.

Feedback and questions are welcome

If you use this and like it, have trouble getting it working, or have questions about doing more stuff with it, drop me a note! My email is andrew@neitsch.ca.

Introduction

Everyone who works with Django has worked their way through the Django tutorial, building the polls app and running it on their local machine. It’s fun and easy to go from there to building little Django apps for your own use. But there’s a huge jump to go from running Django sites on your local machine to running them on the web. Instead of a simple manage.py command, you need to configure apache modules and stuff like that, which requires a publicly-accessible webserver that’s properly configured, secured, and monitored, which can be a lot of work and expense for a toy site.

In the old days when people wrote static web sites, deployment was easy: you’d pay a few dollars a month for a shared web host and rsync your files over. The host would monitor and secure the server, and if the site had problems, you’d email support and they’d fix it for you.

It turns out you can still do that with Django: DreamHost is one of the most popular shared web hosts, and you can run as many Django sites as you want on it using their standard hosting plan which costs $5.95–$8.95/month depending on how many months in advance you prepay. For that you get unlimited domains, unlimited databases, and unlimited bandwidth, full SSH access to the server, and support when things break.

This is the basic setup I’ve used for about half a dozen Django projects. It’s allowed me to continuously deploy changes with a minimum of fuss, and with it you can write a new app and get it running on the web in minutes, with push-button update ability.

Preliminary steps

First you need the resources to deploy your site to: a domain, an SSH user, and a database.

1. Log into the DreamHost panel.

2. Under Domains → Manage Domains, click Add New Domain / Sub-Domain

3. Enter the domain name, select “Create a New User” and enter a username, and check off the “Passenger (Ruby/Python apps only)” option. Then click “Fully host this domain.”

4. Under Users → Manage Users, edit the user you just created and change the User Type to a Shell User. Disallow FTP while you’re in there.

5. Under Goodies → MySQL Databases, create a new database. Pick your own username and password.

6. It may take a few minutes for SSH to be enabled for the new user. Once it is, log in and add your SSH public key:

   $ mkdir -m 0700 .ssh
   $ (umask 0077 && cat > .ssh/authorized_keys)
   [paste ~/.ssh/id_rsa.pub from your dev machine]
   ^D
   

7. Configure ssh to remember your username by adding lines like this to ~/.ssh/config:

   Host newdomain.example.org
       User newuser
   

8. Update the DOMAIN in settings.py to point to this new domain.

Getting your site running on DreamHost

You’ll need to do some initial setup on the server, and then push your code to the server.

These steps work with the code in this repository. You can fork this repo, deploy it yourself, then pull out the polls app and add your own. Or, you can look at the commit history of this repo to see the relatively few things that were done to polls to make it deployable.

1. Download the Python source tarball, unpack it, and install it. DreamHost servers have Python already but this gets the latest version and makes it easier to install additional packages.

   $ mkdir src && cd src
   $ wget 'http://www.python.org/ftp/python/2.7.6/Python-2.7.6.xz'
   $ tar xf Python-2.7.6.xz
   $ cd Python-2.7.6
   $ nice sh -c './configure --with-system-expat --prefix=$HOME/local \
       && make -j2 && make install'
   

2. Add $HOME/local/bin to your path in ~/.bashrc and/or ~/.bash_profile as needed, then logout and log back in.

3. Download setuptools to ~/src, unpack it, and install it:

   $ cd ~/src
   $ curl -LO 'https://pypi.python.org/packages/source/s/setuptools/setuptools-2.1.tar.gz'
   $ tar xf setuptools-2.1.tar.gz
   $ cd setuptools-2.1
   $ python setup.py install
   

4. Use easy_install to install pip and mercurial.

   $ easy_install pip mercurial
   

5. Set up the mysql configuration file:

   (umask 0077 && echo '[client]
   password="password"
   host="mysql.example.org"
   user="username"
   database="database_name"' > ~/.my.cnf)
   

6. Push your code to the server.

   On the server:

    $ mkdir ~/hg
    $ cd ~/hg
    $ hg init
   

   Then on your local machine, update .hg/hgrc with the new path:

    [paths]
    default-push = ssh://newdomain.example.org/hg
   

   and run hg push.

7. Now run ./manage.py deploy on your local machine and you’re good to go!

8. To add a superuser on the server, run

   ssh -t newhost.example.org newhost.example.org/code/manage.py createsuperuser
   

Deploying changes to DreamHost

Run ./manage.py deploy. That’s it!

Demo

Andrew logs in to the DreamHost web panel, creates a new subdomain, updates DOMAIN in settings.py, waits for DNS to propagate, runs deploy, and immediately gets a deployed website. “Hello world” is added to a page, deploy is run, and the live site picks up the new text.

The actual presentation did not go quite this smoothly, and I sort of blamed DreamHost, but it was really my forgetting to configure ALLOWED_HOSTS properly.

Questions

• How scalable is this?

  One website I helped set up with this was once linked to by a very popular blog and started getting around 15 requests/s at which point it basically fell over. My friend tweaked some things like caching and moving some things to be served statically instead of dynamically, and subsequent testing showed that it would be able to stand 30 requests/s.

  I think we were using a DreamHost VPS at that point though—if your site is using tons of CPU or you want better performance, you can move it from the shared hosting environment at DreamHost to a VPS that you get root access on for around $50/month extra.

• My site uses a third-party library like markdown. How do I deploy that?

  Just add it to requirements.txt, commit, and run manage.py deploy. The deploy script automatically installs everything in there.

• What about database migrations?

  Add South to requirements.txt, and update the deploy management command to pass --migrate to syncdb, or wait for Django 1.7.

Next steps

• Pingdom is an awesome web service that checks your website every minute to make sure it’s up and displaying the right stuff. It has two great functions with DreamHost: it alerts you to check your code and/or contact DreamHost support if there’s ever a problem with your site, and since it visits your site every minute, the Django processes on the server never time out and you don’t get a delayed load when someone first visits your low-traffic site.

• See the Django Deploying Checklist for other Django-specific deployment steps.

• See the Web Operations textbook for guidance on keeping your site running smoothly and professionally, setting up logging, monitoring, and alerting, tuning your database, and much more.

• See Continuous Delivery for how to build more advanced high-availability deployment pipelines.

Future work

If anyone’s interested, or if I need the functionality myself, here are some ways that this could be extended:

• This setup doesn’t let your site send email, but DreamHost absolutely allows you to send email. These instructions could be updated to include how to set that up.

• Automating database and log file backups. This is made easier by the fact that DreamHost unix users can install crontabs.

• The deployment command could take a revision argument to support rollbacks.

• Instead of requiring people to add deployment stuff to individual sites, the deploy command and the stuff it needs could be packaged as its own PyPI module. Instead of forking this module or reproducing the steps in the commit history, making a project deployment could be as simple as adding a module to requirements.txt and INSTALLED_APPS.

• DreamHost actually offers an API that lets you create and edit domains, users, databases, and email addresses. All the steps in this document could be totally automated and packaged in a module. That way, you could just add a new deployment app to the project, and run something like ./manage.py --deploy --initial newsubdomain.example.org to have everything automatically set up for you.

It would be really cool if this grew into something that could automate initial and continuous deployment of Django apps to different web hosts!