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title: Configure Rake Tasks for Deployed Apps
owner: Buildpacks
<strong><%= modified_date %></strong>
For <%=vars.product_short%> to automatically invoke a Rake task while a Ruby or Ruby on Rails app is deployed, you must do the following:
* Include the Rake task in your app
* Configure the application start command using the `command` attribute in the application manifest
The following is an example that shows how to invoke a Rake database migration task at application startup.
1. Create a file with the Rake task name and the extension `.rake`, and store it in the `lib/tasks` directory of your application.
1. Add the following code to your rake file:
<pre class="code">
namespace :cf do
desc "Only run on the first application instance"
task :on_first_instance do
instance_index = JSON.parse(ENV["VCAP_APPLICATION"])["instance_index"] rescue nil
exit(0) unless instance_index == 0
This Rake task limits an idempotent command to the first instance of a deployed application.
1. Add the task to the `manifest.yml` file with the `command` attribute, referencing the idempotent command `rake db:migrate` chained with a start command.
<pre class="code">
&#8208; name: my-rails-app
command: bundle exec rake cf:on_first_instance db:migrate && rails s -p $PORT