Change default Rust distribution downloads from .tar.gz to .tar.xz #2399
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UebelAndre
approved these changes
Jan 5, 2024
auto-merge was automatically disabled
January 5, 2024 19:27
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Rust infra folks requested that I send this change.
According to Rust's logs, currently 30% of bytes served by static.rust-lang.org are .gz tarballs, and primarily that is attributed to Bazel according to user-agent.
The .gz tarballs are needlessly large and consume more bandwidth for Rust than we want to serve.
This PR changes rules_rust to default to .xz tarballs instead. Rustup has been using xz downloads for the past 6.5 years.
The default set of tars downloaded by rules_rust (rustc, rust-std, cargo, clippy, rustfmt, llvm-tools) is 215M in gz and 127M in xz, which is 41% smaller. If adopted, this PR would save static.rust-lang.org more than 12% of its bandwidth.
As a tradeoff, decompressing that set of 6 files with xz is slower: 3.6 seconds for gz and 8.4 seconds for xz. (Single-threaded. If Bazel extracts different files in parallel than the magnitude of the difference would be smaller but the ratio is similar.)
In rust-lang/infra-team#89 we intend to sunset gz downloads, or do something to push users away from them (such as throttling), so gz will be the wrong choice no matter what. To make up for decompression speed we are investigating providing zstd tarballs in rust-lang/infra-team#97 which decompress significantly faster than gz while being not much larger than xz.