PyPI and npm downloads look up the publish time before the cache. When
that lookup fails, a file that is already cached is now served, and only
a cache miss fails with 502 or 503. The proxy keeps serving what it has
while the upstream is unreachable, and nothing new is fetched unchecked.
Also drops the unattached comment block in cooldown_fail_closed.go.
RubyGems, Hex and PyPI keep publish times outside the metadata clients
read, so cooldown fetches them from a second API. When that fetch
failed, was rate limited, or returned something that didn't parse, the
compact index, Hex package or simple page was served unfiltered, and a
Hex package that couldn't be re-encoded was passed on as upstream sent
it. A flaky or rate-limited timestamp API let every version in
cooldown through.
These now fail with 502, or with 503 and Retry-After when the rate
limit gate held the request, as the Go handler already does. PyPI file
downloads check the same way. A PyPI package the JSON API answers 404
for still has no times and is served unfiltered, as before.
npm, Composer, pub.dev and PyPI JSON metadata that couldn't be
rewritten was also passed on unfiltered unless the package had denied
versions. It now fails with 502 whenever cooldown applies too. npm
tarball downloads whose packument couldn't be fetched skipped the
cooldown check and downloaded straight from upstream; they now fail.
All of this only applies when cooldown covers the package: packages
exempted with a duration of 0 skip the timestamp lookups, and the gem
and Hex handlers serve them through the metadata cache as when cooldown
is off.
