Copilot commented on code in PR #13769:
URL: https://github.com/apache/trafficserver/pull/13769#discussion_r4156621076
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src/proxy/http/HttpTransact.cc:
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@@ -5112,6 +5112,49 @@
HttpTransact::handle_no_cache_operation_on_forward_server_response(State *s)
return;
}
+// Revalidation merges in older builds deleted and re-added caching headers on
every 304, and a cache
+// round trip left each dead slot unreclaimable, so a long-lived object's
cached response could grow
+// to hundreds of field blocks. Deleted slots are now reused, but a header's
blocks are never
+// released and every copy and marshal keeps them, so such a header stays
bloated for as long as it
+// is cached and each revalidation rewrites all of it. When it holds well over
the blocks its live
+// fields need, replace it with a copy of just its live fields, in slot order
so field and duplicate
+// order are unchanged. The copy has to land in a fresh heap: copying onto the
existing one frees the
+// dead blocks but leaves their space inside the region that marshal writes to
disk.
+bool
+HttpTransact::compact_cached_response_header(HTTPHdr *cached_header)
+{
+ int blocks = 0;
+
+ for (MIMEFieldBlockImpl const *fblock =
&cached_header->m_mime->m_first_fblock; fblock != nullptr; fblock =
fblock->m_next) {
+ ++blocks;
+ }
+ int const live = cached_header->fields_count();
+
+ if (blocks <= live / MIME_FIELD_BLOCK_SLOTS + 2) {
+ return false;
+ }
+
+ int const before = cached_header->m_heap->marshal_length();
+ HTTPHdr compact;
+
+ compact.create(HTTPType::RESPONSE, cached_header->version_get());
Review Comment:
`HTTPHdr::create` does not assign this version to `m_version`;
`http_hdr_init` hardcodes `HTTP_1_0` and uses the argument only to add HTTP/2/3
pseudo-fields (`src/proxy/hdrs/HTTP.cc:226-255`). Consequently, compaction
downgrades an HTTP/1.1 cached response to HTTP/1.0, and for HTTP/2/3 can inject
a synthetic `:status` before copying the existing fields. Create the empty
response without protocol pseudo-fields and then set its version explicitly.
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