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Default to no Docker image compression in local environment

Pedro Pombeiro (OOO from July 16th till Aug 7th) requested to merge 27503-configurable-compression into master

What does this MR do?

It makes the compression level used by the Makefile to generate tarfiles default to no compression, but still use maximum compression on CI jobs.

Comparison of compression levels (on Mac):

$ tar --version
bsdtar 3.3.2 - libarchive 3.3.2 zlib/1.2.11 liblzma/5.0.5 bz2lib/1.0.6

$ la out/helper-images/prebuilt-x86_64.?.tar.xz
-rw-r--r--  1 pedropombeiro  staff    22M Jan 27 19:25 out/helper-images/prebuilt-x86_64.0.tar.xz
-rw-r--r--  1 pedropombeiro  staff    21M Jan 27 19:26 out/helper-images/prebuilt-x86_64.1.tar.xz
-rw-r--r--  1 pedropombeiro  staff    18M Jan 27 19:27 out/helper-images/prebuilt-x86_64.2.tar.xz
-rw-r--r--  1 pedropombeiro  staff    18M Jan 27 19:29 out/helper-images/prebuilt-x86_64.3.tar.xz
-rw-r--r--  1 pedropombeiro  staff    17M Jan 27 19:31 out/helper-images/prebuilt-x86_64.4.tar.xz
-rw-r--r--  1 pedropombeiro  staff    16M Jan 27 19:33 out/helper-images/prebuilt-x86_64.5.tar.xz
-rw-r--r--  1 pedropombeiro  staff    16M Jan 27 19:36 out/helper-images/prebuilt-x86_64.6.tar.xz
-rw-r--r--  1 pedropombeiro  staff    16M Jan 27 19:39 out/helper-images/prebuilt-x86_64.7.tar.xz
-rw-r--r--  1 pedropombeiro  staff    14M Jan 27 19:42 out/helper-images/prebuilt-x86_64.8.tar.xz
-rw-r--r--  1 pedropombeiro  staff    14M Jan 27 19:45 out/helper-images/prebuilt-x86_64.9.tar.xz

FWIW, the difference in time required to compress at level 8 and level 9 is only 10 seconds, so probably not worth changing it.

Why was this MR needed?

While developing the Runner, we often need to rebuild the Dockerfiles for the helper image, and that entails an xz -f -9 command, selecting the highest level of compression. This is wasteful for a development environment, where we should favor speed over disk space.

What's the best way to test this MR?

  • Check the helper image job artifacts to see if the image size is still the same as in master
  • Run make helper-dockerarchive-host and notice that xz -f -0 is run at the end, resulting in a much faster job.

What are the relevant issue numbers?

Closes #27503 (closed)

Edited by Pedro Pombeiro (OOO from July 16th till Aug 7th)

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