Preparing Your App - Converting an existing Spring Boot app to use Dokku

Here are things that must be true about your app in order to deploy it on UCSB ECI’s implementation of Dokku:

Define spring.port in application.properties

In the file src/main/resources/application.properties you will need this line:

server.port=${PORT:8080}

This line says: if the variable PORT is defined, use that value; otherwise use 8080. This is necessary because in the Dokku environment, the server runs on port assigned by the environment variable PORT, and then that server is proxied through Nginx and exposed on the internet on port 80.

Failing to set this up is one of the reasons you might end up with the following screen:

Seeing that the server is running on port 8080 in your Dokku log can be another indication that this wasn’t done properly.

Define PRODUCTION=true

You will need to do this command at the command line on your assigned dokku-nn.cs.ucsb.edu server:

dokku config:set app-name-here PRODUCTION=true

Where app-name-here is the name of the application that shows up when you do dokku apps:list (e.g. jpa03-cgaucho or team02-prod).

If you don’t, you’ll get something like this:

Failed to connect to the frontend server...
On Dokku, be sure that PRODUCTION=true is defined