ModifyCachingHeaders should not touch Cache-Control headers if downstream-caching is enabled.

[GoogleCodeExporter]

Current behavior:
ModifyCachingHeaders is on by default, and will change all HTML to have 
no-cache Cache-Control headers.
Downstream-caching documentation 
(https://developers.google.com/speed/pagespeed/module/downstream-caching) 
recommends specifying "ModifyCachingHeaders off" so that the downstream cache 
(e.g. varnish) gets access to the origin-server's Cache-control headers for 
HTML, which possibly involve non-zero max-age values. Downstream caches can 
then respect these values wrt caching in their layer, but should carefully 
change these to no-cache on their way out. We also recommend that Etag and 
Last-Modified headers be stripped in the caching layer.

Suggested behavior:
ModifyCachingHeaders should remain on by default. If downstream-caching is 
enabled, we (PSOL) should not touch the "Cache-Control" header but handle all 
other caching-related headers (e.g. Last-Modified, Etag) as before. This will 
ensure that the feature works correctly (and somewhat transparently) with 
downstream-caching and also result in fewer caching-layer-directives in our 
recommendation.

Original issue reported on code.google.com by anup...@google.com on 30 Jul 2013 at 4:34

[GoogleCodeExporter]

Fixed in https://code.google.com/p/modpagespeed/source/detail?r=3585

Original comment by anup...@google.com on 30 Oct 2013 at 2:47

• Changed state: Fixed

[GoogleCodeExporter]

Original comment by hui...@google.com on 31 Oct 2013 at 5:46

• Added labels: Milestone-v30, release-note