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Every Heroku app runs in at least two environments: on the Heroku platform (we’ll call that production) and on your local machine (development). If more than one person is working on the app, then you’ve got multiple development environments - one per machine, usually. Usually, each developer will also have a test environment for running tests.
This separation keeps changes from breaking things. You write code and check the site in development, but you run your tests in the test environment to keep them from overwriting your development database. Similarly, you might have broken features in your development environment most of the time, but you only deploy working code to production.
Unfortunately, this approach breaks down as the environments become less similar. Windows and Macs, for instance, both provide different environments than the Linux stack on Heroku, so you can’t always be sure that code that works in your local development environment will work the same way when you deploy it to production.
The solution is to have a staging environment that is as similar to production as is possible. This can be achieved by creating a second Heroku application that hosts your staging application. With staging, you can check your code in a production-like setting before having it affect your actual users. As you already deploy with git, setting up and managing these multiple remote environments is easy.
Starting from scratch
Say you’ve already got an application on your local machine, and you’re ready to push it to Heroku. We’ll need to create both remote environments, staging and production. To get in the habit of pushing to staging first, we’ll start with it:
$ heroku create --remote staging Creating strong-river-216.... done http://strong-river-216.heroku.com/ | email@example.com:strong-river-216.git Git remote staging added
If you forget the
--remote flag, you can always rename the default
heroku remote later with
git remote rename <old> <new>.
By default, the heroku CLI creates projects with a
heroku git remote (thus the normal
git push heroku master). Here, we’re specifying a different name with the
--remote flag, so pushing code to Heroku and running commands against the app look a little different than the normal
git push heroku master:
$ git push staging master ... $ heroku ps --remote staging === web: `bundle exec thin start -p $PORT -e production` web.1: up for 21s
Once your staging app is up and running properly, you can create your production app:
$ heroku create --remote production Creating fierce-ice-327.... done http://fierce-ice-327.heroku.com/ | firstname.lastname@example.org:fierce-ice-327.git Git remote production added $ git push production master ... $ heroku ps --remote production === web: `bundle exec thin start -p $PORT -e production` web.1: up for 16s
You will need to do some work to keep these apps in sync as you continue to develop them. You’ll need to add contributors, config vars, and add-ons to each individually, for instance.
And with that, you’ve got the same codebase running as two separate Heroku apps – one staging and one production, set up identically.
In the example
heroku commands above we’ve specified the target app using the
--remote option. In the course of your normal work, however, you may tire of always typing either
--remote staging or
--remote production at the end of every command. To make things easier, you can use your git config to specify a default app. For example, if you wanted “staging” to be your default remote, you could set it with the following command:
$ git config heroku.remote staging
This will add a section to the project’s
.git/config file that looks something like this:
[heroku] remote = staging
Once this is set up, all
heroku commands will default to the staging app. To run a command on the production app, simply use the
--remote production option.
The pipelines Heroku Labs feature can be used as an alternative method of deploying from staging to production environments.
Starting from an existing app
An alternative way to create a staging application is to fork an existing application.
Imagine you want to duplicate the staging application and use it for integration tests. The following command will do that:
$ heroku fork -a staging integration $ git remote add integration email@example.com:integration.git
Forking an application is very powerful: it copies over the config vars, re-provisions all add-ons, and copies all Heroku Postgres data too. See the documentation on Fork to learn more.
Managing staging and production configurations
Many languages and frameworks support flipping a development/production switch. For example, when in development mode, you may use a different database, have increased logging levels, and send all emails to yourself instead of to end users.
You typically want to do this for the staging apps. For example, in Ruby you can set the
RAILS_ENV for your staging app (you’ll also need a
config/environments/staging.rb file to make this work, of course.):
$ heroku config:set RACK_ENV=staging RAILS_ENV=staging --remote staging
The services and libraries that your application uses may also need their own configuration variables set, mirroring those on production. For example, you may use a different S3 bucket in development than you do on production, so you will use different values for the keys:
$ heroku config:set S3_KEY=XXX --remote staging $ heroku config:set S3_SECRET=YYY --remote staging
Advanced: Linking local branches to remote apps
It’s simple to type
git push staging master and
git push production master when you’ve followed the steps above. Many developers like to take advantage of git’s branches to separate in-progress and production-ready code, however. In this sort of setup, you might deploy to production from your
master branch, merging in changes from a
development branch once they’ve been reviewed on the staging app. With this setup, pushing is a littler trickier:
$ git push staging development:master
This command tells git that you want to push from your local
development branch to the
master branch of your
staging remote. (It might look a little disorderly, but there’s a lot more going on - take a look at the git book for a very in-depth exploration of refspecs.)
If you want to simplify your git commands, you can make things easier by forcing your local git branches to track your remote applications. Assuming you’ve got git remotes for
production, you can do the following:
If you want to set
push.default for all git repositories (instead of just this one), add
--global to the command.
$ git config push.default tracking $ git checkout -b staging --track staging/master Branch staging set up to track remote branch master from staging. Switched to a new branch 'staging'
Now, you’re in the
staging branch and you’re set up so that
git pull and
git push will work against your staging environment without any further arguments. Change some code, commit it, and push it up:
$ git commit -a -m "changed code" $ git push Counting objects: 11, done. ...
Notice that you said
git push, not
git push staging staging:master. The
push.default setting is what makes this possible; with that set to
tracking, your local branches will automatically push changes to the remote repositories that they track.
If you’d like your local
master branch to point to your
production remote (and you’re running git 1.7 or later), you can do the following:
$ git fetch production $ git branch --set-upstream master production/master
And with that,
git push from
master will update your production app on Heroku.