Copilot commented on code in PR #13611:
URL: https://github.com/apache/trafficserver/pull/13611#discussion_r4016566996
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src/proxy/http/HttpTransact.cc:
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@@ -2724,6 +2724,22 @@ HttpTransact::HandleCacheOpenReadHitFreshness(State *s)
s->cache_lookup_result = HttpTransact::CacheLookupResult_t::HIT_STALE;
}
+ // An object found under the 9.2 key cannot be revalidated: the write that
+ // would apply a 304 is a create on the current key, not an update of the
+ // legacy vector, so the cache discards it. Treat a stale one as a miss. The
+ // full response then lands under the current key through the ordinary miss
+ // path and the legacy copy ages out. Only reads migrate; the methods that
+ // invalidate take the delete path, which reaches both keys.
+ if (s->cache_lookup_result == HttpTransact::CacheLookupResult_t::HIT_STALE
&& s->state_machine != nullptr &&
+ CompatCacheKey::is_legacy(s->state_machine->compatibility_cache_lookup)
&&
+ (s->method == HTTP_WKSIDX_GET || s->method == HTTP_WKSIDX_HEAD)) {
+ TxnDbg(dbg_ctl_http_seq, "Stale under the compatibility key, treating as a
miss");
+ s->cache_info.object_read = nullptr;
Review Comment:
This branch changes the legacy hit to MISS but does not clear request
conditionals. `HandleCacheOpenReadMissGoToOrigin()` later calls
`build_request()`, which copies client `If-None-Match` / `If-Modified-Since`;
removal there is conditional on cacheability and `cache_when_to_revalidate`, so
a configuration such as `cache_when_to_revalidate == 4` can still send them
upstream. A 304 then reaches the canonical create without a full response and
the migration is lost. Strip conditional headers unconditionally for this
legacy-stale path after the outbound request is built, using
`HttpTransactHeaders::remove_conditional_headers`.
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