Heroku run Docker image with port parameter

The question is quite old now, but still I will write my answer here if it can be of some help to others.

I have spring-boot App along with swagger-ui Dockerized and deployed on Heroku.

This is my application.yml looks like:

server:  port: ${PORT:8080}  forward-headers-strategy: framework  servlet:   contextPath: /my-appspringdoc:  swagger-ui:    path: '/swagger-ui.html'

Below is my DockerFile configuration.

FROM maven:3.5-jdk-8 as maven_buildWORKDIR /appCOPY pom.xml .RUN mvn clean package -Dmaven.main.skip -Dmaven.test.skip && rm -r targetCOPY src ./srcRUN mvn package spring-boot:repackage########run stage########FROM openjdk:8-jdk-alpineWORKDIR /appRUN apk add --no-cache bashCOPY --from=maven_build /app/target/springapp-1.1.1.jar ./#run the app# 256m was necessary for me, as I am using free version so Heroku was giving me memory quota limit exception therefore, I restricted the limit to 256mENV JAVA_OPTS "-Xmx256m"ENTRYPOINT  ["java","${JAVA_OPTS}", "-jar","-Dserver.port=${PORT}", "springapp-1.1.1.jar"]

The commands I used to create the heroku app:

heroku createheroku stack:set container

The commands I used to build image and deploy:

docker build -t app-image .heroku container:push webheroku container:release web

Finally make sure on Heroku Dashboard the dyno information looks like this:

web java \$\{JAVA_OPTS\} -jar -Dserver.port\=\$\{PORT\} springapp-1.1.1.jar

After all these steps, I was able to access the swagger-ui via

https://testapp.herokuapp.com/my-app/swagger-ui.html

Your Docker container is required to listen to HTTP traffic in the port specified by Heroku.

Looking at the Dockerfile in the Github repo for swaggerapi/swagger-ui, it looks like it already supports the PORT environment variable: https://github.com/swagger-api/swagger-ui/blob/be72c292cae62bcaf743adc6236707962bc60bad/Dockerfile#L13

So maybe you don't really need to do anything?It looks like this image would just work, if shipped to Heroku as a web app.