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Asked: 2026-06-18T14:32:03+00:00

Although this question should be trivial, I didn’t success to enable browser caching on

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Although this question should be trivial, I didn’t success to enable browser caching on web google app engine java server.

I’ve try to put this kind of thing in my appengine-web.xml:

<static-files>
  <include path="/**.cache.**" expiration="365d" />
...

but when I’m looking the response header I find this in local:

Content-Length: 196084
Cache-Control: public, max-age=31536000
Expires: Fri, 10 Jan 2014 19:40:45 GMT
Content-Type: image/png
Last-Modified: Tue, 18 Dec 2012 21:41:22 GMT
Server: Jetty(6.1.x)

Which is fine… but this in production environment:

HTTP/1.1 304 Not Modified
ETag: "RV4Bpg"
X-AppEngine-Estimated-CPM-US-Dollars: $0.000000
X-AppEngine-Resource-Usage: ms=109 cpu_ms=0
Date: Thu, 10 Jan 2013 19:41:20 GMT
Pragma: no-cache
Expires: Fri, 01 Jan 1990 00:00:00 GMT
Cache-Control: no-cache, must-revalidate
Server: Google Frontend

Which is definitively not what I want 🙁

Any idea ? something I’ve missed ?

[EDIT]
for not yet downloaded content, my browser receive the following header:

HTTP/1.1 200 OK
ETag: "RV4Bpg"
Date: Fri, 11 Jan 2013 12:50:50 GMT
Expires: Sat, 11 Jan 2014 12:50:50 GMT
Cache-Control: public, max-age=31536000
X-AppEngine-Estimated-CPM-US-Dollars: $0.000000
X-AppEngine-Resource-Usage: ms=3 cpu_ms=0
Date: Fri, 11 Jan 2013 12:50:50 GMT
Pragma: no-cache
Expires: Fri, 01 Jan 1990 00:00:00 GMT
Cache-Control: no-cache, must-revalidate
Content-Type: image/png
Server: Google Frontend
Content-Length: 196084
Proxy-Connection: Keep-Alive
Connection: Keep-Alive
X-RBT-Optimized-By: eu-dcc-sh02 (RiOS 6.5.5b) SC

An ETag and several contradictory ‘Expires’ and ‘Cache-Control’ …
Is there several way to configure caching policy ? Could it come from my ISP ? or a proxy ?

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1 Answer

  1. Editorial Team

    When you are logged in to a Google App Engine application as an administrator:

    1. The X-AppEngine-* headers shown in your question are included.
    2. The Cache-Control: no-cache, must-revalidate header is included, because the X-AppEngine-* headers are private and must not be cached.

    This is hidden at the end of the Responses section at https://developers.google.com/appengine/docs/python/runtime#Responses, which says that:

    Responses with resource usage statistics will be made uncacheable.

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