Docker buildpack build fails on RHEL: Only Ubuntu is supported at present, requested distribution: rhel

Issue

Mendix Docker buildpack fails with the following error:

INFO: Selecting Mono Runtime: 5

Traceback (most recent call last):
File "/opt/mendix/buildpack/./compilation.py", line 76, in <module>
compilation_globals = call_buildpack_compilation()
File "/opt/mendix/buildpack/./compilation.py", line 61, in call_buildpack_compilation
return runpy.run_module("buildpack.stage", run_name="__main__")
File "/opt/mendix/buildpack/buildpack/core/mxbuild.py", line 25, in build_from_source
mono_location = mono.ensure_and_get_mono(...)
File "/opt/mendix/buildpack/buildpack/core/mono.py", line 50, in _compose_mono_dependency_name
raise Exception(
Exception: Only Ubuntu is supported at present, requested distribution: rhel

Environment

Applications deployed with Docker

Cause

When an application is a source Mendix Package (MPK) file, a Modeler Project Repository (MPR) project directory, or a compressed Mendix Deployment Archive (MDA) file, it must be converted or compiled into a format supported by Cloud Foundry (CF) Buildpack. The build.py script performs this conversion by compiling the source into an extracted MDA format in the destination directory. If the build.py script is not executed before the container build, the build process attempts to compile the source directly, which is no longer supported by the CF buildpack for Mendix 8, 9, and 10 versions. This results in a build failure with the Mono dependency error.

Additionally, using unsupported branches, such as master instead of the maintained latest branch documentation will lead to this issue.

Solution/Workaround

Follow the validated Docker buildpack procedure for building from source.

1. Use the maintained Docker buildpack documentation from the latest branch, not the master branch.

2. Compile the source MPK file or MPR project directory, or compressed MDA file, into an extracted MDA format by running the build.py script:

   /build.py --source <path-to-source> --destination <destination-dir> build-mda-dir

3. After the build.py script completes, build the Docker image from the generated destination directory: 

   docker build --build-arg BUILDER_ROOTFS_IMAGE=mendix-rootfs:builder --build-arg ROOTFS_IMAGE=mendix-rootfs:app --tag <image-tag> <destination-dir>

Additional information

Mendix documentation: Compile MDA for Mendix Docker Buildpack