Copilot commented on code in PR #12946:
URL: https://github.com/apache/trafficserver/pull/12946#discussion_r2897980653
##########
doc/admin-guide/plugins/compress.en.rst:
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@@ -98,10 +99,21 @@ Per site configuration for remap plugin should be ignored.
cache
-----
-When set to ``true``, causes |TS| to cache both the compressed and uncompressed
-versions of the content as :term:`alternates <alternate>`. When set to
-``false``, |TS| will cache only the compressed or decompressed variant returned
-by the origin. Enabled by default.
+Controls which version of the response is stored in cache when the compress
+transform runs (i.e., when the client sends ``Accept-Encoding``).
+
+When set to ``true``, the compressed (transformed) response is cached. When set
+to ``false``, the uncompressed (untransformed) response is cached and
+compression is performed on-the-fly for subsequent cache hits.
+
+.. note::
+
+ The plugin always adds ``Vary: Accept-Encoding`` to compressible responses.
+ This causes |TS| to store compressed and uncompressed responses as separate
+ :term:`alternates <alternate>`, so both variants will be cached after
clients
+ of each type have made a request — regardless of this setting.
Review Comment:
The note says `Vary: Accept-Encoding` means both compressed and uncompressed
variants “will be cached … regardless of this setting”, but with `cache false`
the plugin explicitly disables transformed-response caching (see
`TSHttpTxnTransformedRespCache(txnp, 0)` in `compress_transform_add()`), so the
compressed variant is generally not stored in cache. Please reword this note to
clarify that `Vary: Accept-Encoding` creates separate cache alternates/keys for
requests with different `Accept-Encoding`, but which body representation is
stored still depends on the `cache` option (and with `cache false` compression
is done on-the-fly).
```suggestion
This causes |TS| to use separate cache :term:`alternates <alternate>`
(keys)
for requests with different ``Accept-Encoding`` values. Which body
representation is actually stored in cache still depends on the ``cache``
option: with ``cache true`` the compressed response is cached, while with
``cache false`` only the uncompressed response is cached and compression
is
performed on-the-fly for clients that send ``Accept-Encoding``.
```
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