A response arriving during a hold was sent before it began, so a late
success no longer releases the host; only one after the hold has ended
does.
Artifact fetches check RateLimitGate.Held before calling the fetcher, so
held cache misses fail with the HeldError without counting as failures
in the host's circuit breaker.
Every handler that answers an upstream fetch error with 502 now answers
a held request with 503 and Retry-After instead.
OnHold and RecordUpstreamRateLimitHold drop the unused duration.
A 429, or a 503 with Retry-After, from an upstream host now stops the
proxy sending that host anything for as long as it asked (capped at an
hour), or for a minute doubling up to fifteen when no Retry-After came.
Held requests fail locally: cached metadata is served stale as before,
and anything uncached answers 503 with the remaining Retry-After so the
client paces itself too.
The gate is a RoundTripper under the auth transport, so metadata,
artifact and passthrough fetches all obey it. Metadata fetches had no
retry or circuit breaker, so a rate-limited upstream kept receiving one
request per cache miss for the whole block. /health lists held hosts
under upstream_holds and proxy_upstream_rate_limit_holds_total counts
holds.
Credentials configured for a token service were applied to any challenge
naming it. A host the proxy fetches from, such as one in a Composer dist
URL or a Helm index, could answer a /v2/ request with a Bearer challenge
naming that realm, and the proxy fetched a token with the configured
credentials and sent it to that host. A token cached from a legitimate
pull was handed over the same way.
- Follow a challenge to a realm with configured credentials only for a
registry that has configured credentials of its own, or is on the same
site (registrable domain) as the realm, as registry-1.docker.io is with
auth.docker.io; otherwise pass the 401 back
- Keep following anonymous challenges for any registry, as before
- Document the rule
