Trouble with Heroku buildpacks and environment variables

I recently migrated from Heroku to render. Everything is working fine, except that deployments are slow.

The application is build using maven, and the problem is that the MAVEN_CUSTOM_GOALS are being ignored.

During the migration from Heroku:

The environment variables MAVEN_CUSTOM_GOALS and MAVEN_CUSTOM_OPTS were correctly brought into the environment.

And the Dockerfile.render file was created with:

ARG HEROKU_STACK=v2-heroku-20

When I read the deployment logs, I see that the maven build runs with the command ./mvnw -DskipTests clean dependency:list install which is the default for heroku-buildpack-java.

How can I get these environment variables to flow through and affect the build?

Hey there,
If you crack open the Dockerfile.render that was created, in there you should see a commented-out section of ARG examples to bring into the environment at build time - you’ll need to list whatever environment variables you want available to the build in there,


John B

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Thanks, I appreciate the answer, and I’ll look into using ARGs. However, the generated Dockerfile.render file doesn’t have a section of ARG examples. Here’s the generated file in its entirety.

# "v2-" stacks use our new, more rigorous buildpacks management system. They
# allow you to use multiple buildpacks in a single application, as well as to
# use custom buildpacks. We do not support using the original stack images with
# @renderinc/heroku-import v3.0.0 and above.
ARG HEROKU_STACK=v2-heroku-20

# The FROM statement above triggers the following steps
# 1. Copy the contents of the directory containing this Dockerfile to a Docker image
# 2. Build the app using the appropriate Heroku buildpacks. This supports both Heroku and custom buildpacks.

# For running the app, we use a clean base image and also one without Ubuntu development packages

# Copy build artifacts to runtime image
COPY --from=builder --chown=1000:1000 /render /render/
COPY --from=builder --chown=1000:1000 /app /app/

# Switch to non-root user
USER 1000:1000

# Source all /app/.profile.d/*.sh files before process start.
# These are created by buildpacks.
ENTRYPOINT [ "/render/setup-env" ]

# 3. By default, run the 'web' process type defined in the app's Procfile
# You may override the process type that is run by replacing 'web' with another
# process type name in the CMD line below. That process type must have been
# defined in the app's Procfile during build.
CMD [ "/render/process/web" ]

Ah, that looks like an older generation, if you do a heroku update then you’ll get a newer version of the plugin and then a new run of the import command and you’ll get a Dockerfile.render which will make sense based on what I said originally


John B

Thank you very much! I was able to reimport, found the ARG section, added two ARGs for the maven environment variables, and everything is working now!

Great, thanks for the update, I’m glad you got things sorted

John B

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