Running on Heroku¶
Normally, deploying a Django site would make you want to flip your desk:
Luckily for us, Heroku has made the process a complete joy! If you’re aren’t familiar with Heroku–they are the best web host, and you will love them if you don’t already.
django-skel ships with a production ready Heroku configuration module, and this section will walk you through creating your Heroku app, and getting your site running in production.
While this section is quite long, don’t be intimidated! It’s only long because I’m explaining everything along the way–the reality of it is that deploying your site this way really only consists of a couple commands.
If you’d like to read some official documentation on the topic, check out Heroku’s Django documentation.
Step 1 - Create Your Heroku Application¶
The first step in getting your site running on Heroku is, as I’m sure you’ve guessed, to create a Heroku app! Let’s do it now:
$ heroku create [your_app_name_here]
If you don’t specify an app name, one will be automatically assigned to you. I like to name my apps explicitly, because I have a bunch of them, and it’s a lot easier to track.
The next thing you’ll need to do is push your project code to Heroku. When you ran the heroku create command above, the heroku command added a new Git remote to your project. To push your code to Heroku, all you do is push to the heroku remote:
$ git push heroku master
That will ‘deploy’ your code straight to Heroku! From now on, whenever you want to deploy your code, just run this command.
Step 2 - Install the Addons¶
Now that you’ve got your Heroku application going, let’s install some Heroku Addons. Heroku is a modular system. The core of Heroku allows you to run your code, but doesn’t provide any extra infrastructure services.
To get things like PostgreSQL, memcache, RabbitMQ, etc.–you need to install Heroku addons to do what you want.
Let’s install our required addons now–these addons are all free (you can upgrade them at any time in the future). django-skel already supports all of these, and requires most of them to function:
$ heroku addons:add cloudamqp:lemur $ heroku addons:add heroku-postgresql:dev $ heroku addons:add scheduler:standard $ heroku addons:add memcachier:dev $ heroku addons:add newrelic:standard $ heroku addons:add pgbackups:auto-month $ heroku addons:add sentry:developer
cloudamqp is a hosted RabbitMQ service. This is what makes our task queueing (via Celery) possible.
heroku-postgresql is a hosted PostgreSQL service that kicks ass.
scheduler is a cron replacement.
memcachier is a hosted memcache service.
newrelic is the best application monitoring tool ever created.
pgbackups is an excellent PostgreSQL backup tool that stores backups automatically to S3, and lets you download and manage your backups easily.
sentry is a pretty neat error aggregation and searching tool that makes debugging issues simple.
Just for the record, if you’d like to upgrade any of these free addons, you can do so by running the heroku addons:upgrade command. For example–to switch from the free newrelic addon to their paid addon which has lots more features, you can simply run:
$ heroku addons:upgrade newrelic:professional
The last thing you’ll need to do is specify a default PostgreSQL database (django-skel requires this). To do this, run:
$ heroku pg:info
And you should see a database name, something like HEROKU_POSTGRESQL_NAVY. Once you’ve got that name, run:
$ heroku pg:promote HEROKU_POSTGRESQL_NAVY
To set your database as the default.
Step 3 - Configure the Environment¶
Heroku operates via environment variables. This is the preferred place to store all those secret things (passwords, API keys, etc.) that you don’t want lurking around your version control system.
django-skel requires several environment variables be set. To set these variables, run the following commands:
# Your AWS security credentials: $ heroku config:add AWS_ACCESS_KEY_ID=xxx $ heroku config:add AWS_SECRET_ACCESS_KEY=xxx $ heroku config:add AWS_STORAGE_BUCKET_NAME=xxx # Replace 'woot' with the name of your project: $ heroku config:add DJANGO_SETTINGS_MODULE=woot.settings.prod # A random long (40 characters or so) string: $ heroku config:add SECRET_KEY=xxx
Not sure what to use for your SECRET_KEY setting? You can always do something like:
from random import choice print ''.join([choice('abcdefghijklmnopqrstuvwxyz0123456789!@#$%^&*(-_=+)') for i in range(50)])
And copy the resulting string for usage :)
If you’d like to, you can also enable email support out of the box by setting the optional email environment variables as well:
$ heroku config:add EMAIL_HOST=xxx $ heroku config:add EMAIL_HOST_PASSWORD=xxx $ heroku config:add EMAIL_HOST_USER=xxx $ heroku config:add EMAIL_PORT=xxx
EMAIL_HOST and EMAIL_PORT will default to the proper settings for Google apps, so if you’re using that–feel free to leave those out.
Step 4 - Spin It Up!¶
Now that everything is configured and ready to go, let’s spin up our backend!
Instead of spinning up ‘servers’, Heroku allows us to spin up ‘dynos’, which are essentially locked-down virtual server instances. The Procfile defined at the root of your django-skel project defines our three service types:
- web - The service that runs our Django application behind gunicorn.
- scheduler - The service that runs a Celery worker and the Celerybeat daemon.
- worker - The service that runs a Celery worker only.
To spin up a web dyno, run: heroku scale web=1. You can confirm that everything is working by running heroku ps afterwards. That will run a single web dyno.
If you’d like run a Celery worker, run: heroku scale scheduler=1. If you need more than one worker, you can add additional power by spinning up the worker dynos, via heroku scale worker=1.
No matter what, never EVER spin up more than one scheduler. The scheduler process runs Celerybeat, which schedules background tasks. Having more than one scheduler running can cause serious duplicate task problems. Instead, you should always have one scheduler running, and as many worker instances as you need.
Need to add more web servers? No problem:
$ heroku scale web=100
Need to add more workers? No problem:
$ heroku scale worker=100
Need to check and see how many dynos you have running? Easy:
$ heroku ps
Step 5 - Deploy Your Static Assets¶
The last step in successfully deploying your production Django application is to compress and then upload all your static assets to Amazon S3 (css, js, images, etc.).
To do this, simply run the following commands:
$ heroku run python manage.py collectstatic --noinput $ heroku run python manage.py compress
And that’s it!
You are now running a best practices Django website, on top of Heroku, using Amazon S3 to serve your static content!
If you’d like to learn more about Heroku, scaling, and stuff like that, you should probably check out my blog because I write about this stuff all the time >:)
Oh, and also, read Heroku’s documentation :)
Now... Go and be happy!