sccache can only cache compilation units whose --emit includes link. That
covers workspace rlibs and nothing else: clippy is metadata-only, and the ~100
test binaries, the rustfs bin and every build script invoke the system linker.
So the headline claim that started this — s3select-query costing 17m13s inside
a 19m32s nextest build — does not by itself justify sccache, because cargo
prints "Compiling" when a crate starts and never when it finishes: that number
is the whole compilation tail, not one crate.
Adding --timings behind a workflow_dispatch input on Cache Warm answers it with
data instead. Read two shares off the report: workspace lib codegen against the
whole build, and s3select-query's own rlib. The plan in rustfs/backlog#1601
adopts sccache only above 50% and 25%; if linking dominates instead, the answer
is mold/lld plus split-debuginfo, which is precisely the region sccache cannot
reach.
Off by default: it doubles the ci-dev build, and this only needs running once
per question. Nothing about the normal warm path changes.
Refs: rustfs/backlog#1598, rustfs/backlog#1601
Two cleanups, neither changing what is built or published.
docker.yml loses its type=gha layer cache. The image build compiles nothing —
it downloads a release zip and runs apk/apt — so the cache could only save the
minute or two those take, against a real correctness problem: with
RELEASE=latest the binary URL is resolved by curl inside a RUN layer, and the
layer key does not include what it resolved to. A rebuild at the same RELEASE
value (a dispatch with version=latest, or a re-run of the same version) would
hit the old layer and ship the previous release's binary. mode=max also drew on
the same repo-wide 10GB Actions cache quota the Rust lanes are contending for.
Only RELEASE is passed as a build-arg now; it is the sole one the Dockerfiles
declare besides TARGETARCH. BUILDTIME, VERSION, BUILD_TYPE, REVISION and CHANNEL
were read by no stage, and BUILDTIME's $(date ...) was a literal string in the
YAML block rather than a substitution. The DOCKER_CHANNEL computation that fed
CHANNEL evaluated to "release" down every branch and is gone with it. BUILD_DATE
and VCS_REF stay unset even though the Dockerfiles declare them: supplying them
would change the published image labels.
The setup composite stops installing tools its callers do not use. protobuf-
compiler comes out of the apt list entirely — setup-protoc installs 34.1 into
the tool cache and prepends it to PATH, so the apt build was shadowed on every
run and never used; the same duplicate install is removed from the io_uring lane.
musl-tools, zip and unzip move behind install-build-packaging-tools, off for the
CI and coverage lanes and left on for build.yml, whose native musl leg needs
musl-gcc and whose packaging steps need zip. cargo-nextest and the
rustfmt/clippy components move behind install-test-tools, off only for build.yml,
which runs no tests and no lints; coverage and the nightly replication lane keep
them because both invoke nextest.
The action's github-token input is deleted along with its 20 call sites. Its
runs block never referenced it — setup-protoc uses github.token directly — so it
was 20 places handing a token to something that ignored it.
Refs: rustfs/backlog#1598, rustfs/backlog#1600, rustfs/backlog#1603
#5532 consolidated ci.yml's nine cache sites into four keys with one writer
each, but the writers never run to completion: ci.yml cancels superseded runs
on main, and merges land far faster than its 70-minute pipeline. Measured over
15 consecutive main pushes — 12 cancelled, 2 failed, 0 succeeded. A cancelled
run never reaches rust-cache's post step (cache-on-failure does not cover
cancellation), so nothing was being saved and every PR paid a cold restore:
11.8-20.9 minutes of "Setup Rust environment" against 0.7-3.4 warm.
Move cache writing into its own workflow whose concurrency group does not
cancel in progress, and make every lane in ci.yml a pure reader. ci.yml keeps
cancelling superseded runs, which is correct — nobody needs test results for a
commit that is already three merges behind — while the caches still get
written.
Not simply disabling cancel-in-progress for main pushes in ci.yml: that would
run several full pipelines concurrently on a 15-21 runner self-hosted pool that
is already the bottleneck, which is the opposite of the goal. GitHub keeps at
most one running plus one pending run per concurrency group, so the new
workflow collapses a burst of merges into "current finishes, newest queued
follows" and occupies one runner at a time.
The warm builds are supersets of what the reading lanes compile, because a
reader restores only what the writer saved: --all-targets for the test binaries
nextest builds (including e2e_test, which test-and-lint excludes), plus the
e2e-test-hooks and rio-v2 feature combinations, whose different feature
resolution yields a different -Cmetadata. The ci-dev build carries the same
CARGO_BUILD_JOBS limit ci.yml puts on nextest, since it links the same ~100
test binaries and three concurrent links can wedge Cargo (#5394). ci-uring is
warmed on ubuntu-latest to match its reader: rust-cache's key covers runner.os
and arch but not the runner label or image.
Refs: rustfs/backlog#1598, rustfs/backlog#1600
Zhengchao An