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The element bind mounts a pip cache inside the image build chroot so that pip downloads can be reused across image builds. While similar in purpose to the PyPi element that sets up a mirror, this element just allows for a reusable download cache and doesn't require anything to be setup beforehand. The pip-cache element is not concurrency safe, and that is indicated in the README for the element. An upstream bug was file as well: https://github.com/pypa/pip/issues/1141 Change-Id: Ibd1d4ea17c24923ed939357ada95b781e3179cfd
18 lines
730 B
Markdown
18 lines
730 B
Markdown
# Use a cache for pip
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Using a download cache speeds up image builds.
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Including this element in an image build causes
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$HOME/.cache/image-create/pip to be bind mounted as /tmp/pip inside
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the image build chroot. The $PIP_DOWNLOAD_CACHE environment variable
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is then defined as /tmp/pip, which causes pip to cache all downloads
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to the defined location.
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Note that pip and its use of $PIP_DOWNLOAD_CACHE is not concurrency
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safe. Running multiple instances of diskimage-builder concurrently
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can cause issues. Therefore, it is advised to only have one instance
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of diskimage-builder that includes the pip-cache element running at a
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time.
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The pip concurrency issue is being tracked upstream at
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https://github.com/pypa/pip/issues/1141
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