Basic Server Setup (Heroku)¶
Heroku is a commercial cloud hosting provider. If you are not experienced with web server administration, Heroku may be the simplest option for you.
The Heroku free plan is sufficient for small-scale testing of your app, but once you are ready to launch a study, you should upgrade to a paid server, which can handle more traffic. However, Heroku is quite inexpensive, because you only pay for the time you actually use it. If you run a study for only 1 day, you can turn off your dynos and addons, and then you only pay 1/30 of the monthly cost. Often this means you can run a study for just a few dollars.
Heroku setup (quick version)¶
Assuming Heroku is already installed & logged in:
git init git add . git commit -am "my commit message" heroku create heroku addons:create heroku-redis:premium-0 git push heroku master heroku run otree resetdb
Heroku setup (detailed version)¶
Create an account¶
Create an account on Heroku. Select Python as your main language. However, you can skip the “Getting Started With Python” guide.
Install the Heroku Toolbelt¶
Install the Heroku Toolbelt.
This provides you access to the Heroku Command Line utility.
Once installed open PowerShell (Windows) or Terminal (Mac), and go to your project folder.
Log in using the email address and password you used when creating your Heroku account:
$ heroku login
heroku command is not found,
close and reopen your command prompt.
Initialize your Git repo¶
If you haven’t already initialized a git repository run this command from your project’s root directory:
Create the Heroku app¶
Create an app on Heroku, which prepares Heroku to receive your source code:
$ heroku create Creating lit-bastion-5032 in organization heroku... done, stack is cedar-14 http://lit-bastion-5032.herokuapp.com/ | https://git.heroku.com/lit-bastion-5032.git Git remote heroku added
When you create an app, a git remote (called heroku) is also created and associated with your local git repository.
Heroku generates a random name (in this case lit-bastion-5032) for your
app. Or you can specify your own name; see
heroku help create for more info.
heroku help for general help.)
Install Redis add-on¶
You need to install Heroku’s Redis add-on.
If you don’t do it, you will see an “Application Error”:
If Redis is not set up, you may also see messages in your
saying “Connection refused”, or an error mentioning port 6379.
After adding Redis, if it’s still not working,
you may need to wait for a few minutes, or restart with
Upgrade oTree, to get the latest bugfixes:
$ pip3 install -U otree-core
Save to requirements_base.txt¶
The version that is output will look something like
Open the file in your project’s root directory
requirements_base.txt, and modify the line with
to that version. The file should look like this (substitute actual version for
otree-core>=1.X.X # Heroku requires Django to be explicitly in requirements file # in order to run collectstatic Django==1.8.8
Heroku will read this file and install the
same version of each library on your server.
If you are depending on any extra Python libraries (e.g. Numpy or Pandas),
they need to be added to your
Push your code to Heroku¶
Commit your changes (note the dot in
git add .):
git add . git commit -am "your commit message"
Transfer (push) the local repository to Heroku:
$ git push heroku master
Reset the oTree database on Heroku.
You can get your app’s name by typing
$ heroku run otree resetdb
Open the site in your browser:
$ heroku open
(This command must be executed from the directory that contains your project.)
That’s it! You should be able to play your app online. If not, see the next section.
If your app fails to load, e.g. “application error”, try the following:
- Use the command
heroku logsto check the server logs for any error messages (or, better yet, enable Papertrail, which provides a nice UI for browsing logs).
- Make sure you remembered to enable the Heroku Redis add-on (see here).
heroku run otree --versionto check that you are using the latest version of otree-core on Heroku.
Making updates and modifications¶
When you make modifications to your app and want to push the updates to Heroku, enter:
git add . git commit -am "my commit message" git push heroku master # next command only required if you added/removed a field in models.py heroku run otree resetdb
You should also regularly update your requirements_base.txt.
Further steps with Heroku¶
Below are the steps you should take before launching a real study, or to further configure your server’s behavior.
Turn on timeout worker Dyno¶
To enable full functionality, you should go to the Heroku Dashboard,
click on your app, click to edit the dynos, and turn on the
Turning on the second dyno is free, but you may need to register a credit card with Heroku.
If you are just testing your app, oTree will still function without the
but if you are running a study with real participants and your pages have
timeouts defined by
timeout_seconds, then the
timeoutworker will ensure
that the user will be automatically advanced to the next page
even if they closes their browser. This can be useful for online experiments
If you do not see a
timeoutworker entry, make sure your
looks like this:
web: otree webandworkers timeoutworker: otree timeoutworker
To add an existing remote:¶
If you previously created a Heroku app and want to link your local oTree git repository to that app, use this command:
$ heroku git:remote -a [myherokuapp]
Scaling up the server¶
The Heroku free plan is sufficient for small-scale testing of your app, but once you are ready to go live, you need to upgrade to a paid plan.
After you finish your experiment, you can scale your dynos and database back down, so then you don’t have to pay the full monthly cost.
Postgres (upgrade required)¶
You need to upgrade your Postgres database to a paid tier (at least the cheapest paid plan), because the free version can only store a small amount of data.
To provision the “Hobby Basic” database:
$ heroku addons:create heroku-postgresql:hobby-basic Adding heroku-postgresql:hobby-basic to sushi... done, v69 Attached as HEROKU_POSTGRESQL_RED Database has been created and is available
This command will give you the name of your new DB (in the above example,
Then you need to promote (i.e. “activate”) this new database:
$ heroku pg:promote HEROKU_POSTGRESQL_RED # substitute your color here Promoting HEROKU_POSTGRESQL_RED_URL to DATABASE_URL... done
After purchasing the upgraded Postgres, it’s recommended to delete the hobby-dev (free) database, to avoid accidentally using the wrong database.
In the Heroku dashboard, click on your app’s “Resources” tab, and in the “dynos” section, select “Upgrade to Hobby”. Then select either “Hobby” or “Professional”.
You can also increase the number of web dynos, but if you do so, you may need to upgrade your Redis plan also, because more dynos means more Redis connections.
You should not increase the number of timeoutworker dynos.
If running a study, you should upgrade to one of the paid Redis plans, because it allows more connections and gives you more memory, which can prevent the following errors:
- “ConnectionError: max number of clients reached”
- “ResponseError: OOM command not allowed when used memory > ‘maxmemory’.”
Setting environment variables¶
If you would like to turn off debug mode, you should set the
environment variable, like this:
$ heroku config:set OTREE_PRODUCTION=1
However, this will hide error pages, so you should set up Logging with Sentry.
To password protect parts of the admin interface,
you should set
$ heroku config:set OTREE_AUTH_LEVEL=DEMO
More info at Password protection.
Logging with Papertrail¶
If using Heroku, we recommend installing the free “Papertrail” logging add-on:
heroku addons:create papertrail:choklad
Papertrail gives you an easy-to-use interface for exploring the Heroku server logs.
It is much easier to use than running
(This is useful even if you are already using Sentry, because it shows different types of errors.)
When running studies, it is your responsibility to back up your database.