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bazel: run CopyToDirectory locally in CI instead of via the cache - #12092
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maliberty merged 2 commits intoNov 1, 2026
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The hermetic toolchain stages libc++ headers (~1,700 files) with a CopyToDirectory action that every C++ compile depends on. A cache hit for that tree artifact checks every file, and on a cold or busy disk cache it took 160-380 s in CI while all compiles waited. Running the copy locally takes well under a second. Signed-off-by: Matt Liberty <mliberty@precisioninno.com>
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This pull request updates the .bazelrc configuration file to modify the execution info for CI builds. Specifically, it adds build:ci --modify_execution_info=CopyToDirectory=+no-cache to ensure that CopyToDirectory staging runs locally instead of using the disk cache, preventing potential delays on cold or busy disk caches. There are no review comments, and I have no additional feedback to provide.
The Docker and release builds use --config=release, so the CI-only setting did not reach them, and they stalled up to 435 s on the libc++ header tree copy. Signed-off-by: Matt Liberty <mliberty@precisioninno.com>
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The hermetic LLVM toolchain stages the libc++ headers (~1,700 files, 16 MB) into one include directory with a bazel_lib
CopyToDirectoryaction (@llvm-project//libcxx:libcxx_headers_include_search_directory, in both target and exec configs). Every C++ compile in that configuration takes the directory as an input, so nothing downstream can even start a cache lookup until the copy finishes.In CI (e.g. PR-12091-merge #1) this action sat in the
disk-cachestage for 160–380 s on cold or busy nodes while every compile waited ((16 actions, 0 running)). A cache hit on a tree artifact checks every file; running the copy locally takes well under a second.This adds
build:ci --modify_execution_info=CopyToDirectory=+no-cache, so allCopyToDirectoryactions in CI run locally and skip both caches. They are all cheap file copies.