A source-fallback percentage stopped being a readiness signal once
bincraft learned to keep a matching-minor generic binary out of a
fallback's shadow. What survives now is the case where the generic
binary was built under a different minor: unsafe for this client anyway,
so serving source is correct, just slow. Failing on that share would
block slots that are in fact ready - amd64/noble sits at 53% for 4.5 and
4.6 while regressing nobody.
Gate on the thing that decides it instead: packages this client would
receive as source through per-minor routing while the generic slot holds
a binary built under its own minor. That is strictly worse than not
routing, and must be zero. Fallback share is still printed, as context
rather than a verdict.
Measured zero across every reindexed slot and minor.
A Path: target returning 200 is not the same as a per-minor binary
existing. Roughly 53% of steered entries are source fallbacks: they
resolve and install correctly, but they compile on the client, which is
not the binary service we advertise.
Entries without a Built: field are source fallbacks, so this is readable
straight from the index with no downloads.
Falling back to the flat index for an excluded minor is the silent case:
risky packages there are built under another minor and fail at load time,
far from the cause. Send those clients to CRAN for sources instead, which
is what the router already does for an unidentifiable distro.
The whole interaction has to move, not just the index. R resolves tarball
URLs against the repo it was configured with, so serving the index from
CRAN and tarballs from here would hand R a binary where it expects a
source tarball.
A client reporting no R minor at all is not excluded: mirror scripts and
image builds keep getting the flat slot.
- Declare the supported window once in cdn.tf as local.rpkgs_supported_minors
and set KNOWN_MINORS from it on both zones, so the router cannot drift
from build-env-images' LATEST/PREV1/PREV2 unnoticed.
- Split the verification script into supported and excluded minors: the
former must have published indexes, the latter must have none and must
redirect to CRAN under --live.
Enabling UNION_SLOTS today would break every client on an R minor we do
not publish. contribPath() redirects on any minor the User-Agent carries,
without checking that the target exists and without a fallback, and only
4.4, 4.5 and 4.6 are published: a 4.3 client would be sent to a 404 and
see no packages at all.
- Gate routing on KNOWN_MINORS, falling back to the flat index otherwise.
- Honour EXTRA_PUBLIC_HOSTS so the same script can run on a staging zone
and redirect within itself instead of into production.
- Add the cran-rpkgs-test pull zone with UNION_SLOTS pre-enabled, served
on the bunny default hostname so it needs no DNS record.
- Add scripts/verify-r-minor-routing.sh, covering all 16 slots: index
reachability, the union property against flat, Path: target
resolution, coverage parity across minors, and (--live) real
User-Agent routing.
- Cover the fallback in the edge test suite.
