PageSpeed output resources cannot be cached in Google Cloud

[JoyceBabu]

Currently pagespeed adds Cache-Control:max-age=31536000 to optimized resources. Is it possible to add public to it?

Google CDN (alpha) requires 'Cache-Control: public' to be present for resources that must be cached.

[jmarantz]

Hi -- I'm getting some clarification from some people that know more about
the CDN.

On Fri, Mar 11, 2016 at 6:35 AM, Joyce Babu notifications@github.com
wrote:

Currently pagespeed adds Cache-Control:max-age=31536000 to optimized
resources. Is it possible to add public to it?

Google CDN (alpha) requires 'Cache-Control: public' to be present for
resources that must be cached.

—
Reply to this email directly or view it on GitHub
#1149.

[jmarantz]

Adding "public" to the cache-control value is a requirement for Google CDN, but is not required by the HTTP spec. https://cloud.google.com/compute/docs/load-balancing/http/cdn describes the Google requirements, which are pretty clear.

To meet these without adding an unnecessary qualifier for other caches, we can gate this logic on the presence of response-header
Via: 1.1 google

[jmarantz]

Joyce: is it possible for you to add a workaround for this problem in your nginx config? That might help you get better behavior until we can add this functionality to a PageSpeed release.

[JoyceBabu]

I tried disabling all rewriting rules, and using add_header 'Cache-Control' public;. This resulted in two Cache-Control headers

Cache-Control:max-age=604800
Cache-Control: public

Google CDN did not cache those resources, even though it is technically equivalent to Cache-Control:max-age=604800, public

To meet these without adding an unnecessary qualifier for other caches, we can gate this logic on the presence of response-header

Did you mean request-header?

Joyce: is it possible for you to add a workaround for this problem in your nginx config? That might help you get better behavior until we can add this functionality to a PageSpeed release.

I am unable to modify the Cache-Control headers from nginx config. I tried using POSITION_AUX=true, still I am unable to modify the headers. I remember seeing a comment by Jeff in another issue that nginx location blocks targeting optimized resources doesn't work when LoadFromFile is enabled.

[jmarantz]

Yes I meant the Via request-header :)

there is not an nginx equivalent to apache's "header set" directive?

On Sat, Mar 12, 2016 at 3:37 AM, Joyce Babu notifications@github.com
wrote:

I tried disabling all rewriting rules, and using add_header
'Cache-Control' public;. This resulted in two Cache-Control headers

Cache-Control:max-age=604800
Cache-Control: public

Google CDN did not cache those resources, even though it is technically
equivalent to Cache-Control:max-age=604800, public

To meet these without adding an unnecessary qualifier for other caches, we
can gate this logic on the presence of response-header

Did you mean request-header?

Joyce: is it possible for you to add a workaround for this problem in your
nginx config? That might help you get better behavior until we can add this
functionality to a PageSpeed release.

I am unable to modify the Cache-Control headers from nginx config. I tried
using POSITION_AUX=true, still I am unable to modify the headers. I
remember seeing a comment by Jeff in another issue that nginx location
blocks don't when LoadFromFile is enabled.

—
Reply to this email directly or view it on GitHub
#1149 (comment)
.

[JoyceBabu]

there is not an nginx equivalent to apache's "header set" directive?

Yes, there is the add_header directive and the more_set_headers directive. But from what I understand, the header filter appears before ngx_pagespeed in the nginx filter chain. Hence, headers are always intercepted and modified by ngx_pagespeed.

Setting the (experimental) environment variable POSITION_AUX=true is supposed to move ngx_pagespeed's position, so that it will be possible to modify the headers from nginx config. I just found out that it was not working because a change introduced for nginx 1.9.11+ had broken that option. After fixing it, now I am able to do more_set_headers "Cache-Control: max-age=31536000, public";

Thank you.

[jmarantz]

Glad you found a workaround, but I want to leave this open till we fix it properly.

[jmarantz]

This auto-closed when I subbmitted the partial fix: apache/incubator-pagespeed-mod@6d81e80

This fix propagates cache-control:public from origin resources to rewritten resources. However, it does not infer that we need cache-control:public when running inside GCE, which it can do with the "Via" request header, if that includes the substring 'google'.