Heroku launched the review apps beta earlier in May 2015, which completes the continuous delivery experience when deploying on Heroku, along with the Heroku flow. To try out this new flow, I spinned up a rails review app, everything else looks good except that all the assets were broken on the review app server.

It turns out that the assets was depending on an ENV variable, WWW_HOST which is url of the Heroku app and I’ve to fix this manually by doing heroku config:set WWW_HOST=blablabla.com for each review app. But isn’t it too tedious? I think so.

Then I was prying around in the Heroku server and found this HEROKU_APP_NAME which allows me to update the WWW_HOST env via the postdeploy script. I’ve configured the app.json as following:

{
"name":"my-app",
"scripts":{
"postdeploy":"bin/rake dev:bootstrap"
},
"env":{
"MY_SECRET_KEY":{
"required":true
},
"FACEBOOK_URL":{
"required":true
},
"HEROKU_API_TOKEN":{
"required":true
}
},
"addons":[
"heroku-postgresql"
]
}

It should run bin/rake dev:bootstrap after the deployment, and I’ve added a rake task to update the environment variable with Heroku Platform API.

desc 'Bootstrap review app'
task bootstrap: ['db:schema:load', 'db:seed'] do
heroku = PlatformAPI.connect_oauth(ENV['HEROKU_API_TOKEN'])
heroku.config_var.update(ENV['HEROKU_APP_NAME'], 'WWW_HOSTNAME' => "#{ENV['HEROKU_APP_NAME']}.herokuapp.com")
end