build-ubuntu.sh Ignores CPU_CORES Environment Variable

[c-ewing]

Description:

I encountered an issue while using the build-ubuntu.sh script to build Docker images. Despite the ${CPU_CORES} environment variable being set (via check-cpu.sh), CMake utilizes all available cores instead of respecting the specified number.

When check-cpu.sh is run independently, it correctly returns a value of 3. However, during the Docker build process, all cores are still used.

Is this the intended behavior?

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Reproduction Steps:

1. Run check-cpu.sh independently and observe that it returns the expected number of cores.
2. Run build-ubuntu.sh and observe that CMake uses all available CPU cores instead of the value defined in ${CPU_CORES}.

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Expected Behavior:

CMake should respect the ${CPU_CORES} value calculated by check-cpu.sh.

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Relevant Code:
The issue appears to stem from the following lines:

AliceVision/docker/Dockerfile_ubuntu_deps

Lines 73 to 74 in 303ff47

	COPY docker/check-cpu.sh ${AV_DEV}/docker/check-cpu.sh
	RUN export CPU_CORES=`${AV_DEV}/docker/check-cpu.sh` && echo "Build multithreading number of cores: ${CPU_CORES}"

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Proposed Fix:

To ensure the ${CPU_CORES} environment variable is properly calculated and used, I suggest rewriting the lines as:

RUN CPU_CORES=`${AV_DEV}/docker/check-cpu.sh` && \
    echo "Build multithreading number of cores: ${CPU_CORES}" && \
    echo "export CPU_CORES=${CPU_CORES}" >> /etc/profile.d/alicevision.sh

This change will:

1. Execute the check-cpu.sh script to calculate the number of cores.
2. Log the value of CPU_CORES for visibility.
3. Persist the CPU_CORES variable if needed in later build steps by saving it to /etc/profile.d/cpu_cores.sh.

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Next Steps:

If this is indeed an issue, I’m happy to submit a pull request with the proposed fix. If I am misunderstanding the intended behavior, please let me know, and I’ll close this report.

Thank you for your time and support!

Best regards,
cewing

[c-ewing]

Additional Issue: Environment Variables in /etc/profile.d/alicevision.sh Are Not Used in the Build Process

While investigating the original issue, I discovered that none of the environment variables written to /etc/profile.d/alicevision.sh are actually used during the build process.

The root cause is that Docker uses non-login shells for its RUN commands. As a result, the scripts in /etc/profile.d/ are not sourced during the build process. These scripts are only executed if the shell is a login shell, which is not the case for Docker’s default behavior.

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Impact:

Environment variables written to /etc/profile.d/alicevision.sh are effectively ignored during Docker’s build steps and not availible in the future unless a login shell is specifically created.

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Proposed Fix:
To ensure these environment variables are accessible during the build process, the relevant commands should be moved to use the ENV directive in the Dockerfile. For example:

ENV VAR_NAME=value

This approach guarantees that the environment variables are properly set and persist throughout the Docker build process.