[Systems] caching disabled by *.sl.o

[Sascha Silbe]

Hi!

While configuring and testing squid on my new server I noticed most SL 
web services disable or prevent caching from working, thereby severly 
degrading performance and increasing bandwidth usage (both on server and 
client side):


wiki.sugarlabs.org
------------------

Explicitly disabled:

<<<
Expires: Thu, 01 Jan 1970 00:00:00 GMT
Cache-Control: private, must-revalidate, max-age=0
>>>

It's setting Vary properly, so disabling caching has no positive effect 
(other than maybe for some broken browser) that I'm aware of.


bugs.sugarlabs.org
------------------

For Trac it's slightly "better", as it only sets must-revalidate (but 
without giving Expires or max-age, so behaviour isn't strictly defined). 
But since it doesn't support If-Modified-Since (even on single tickets), 
the result is the same (the whole page always gets fully refetched).


www.sugarlabs.org
-----------------

Not cached when using default squid settings because Last-Modified (LM) 
is not given. Does not support If-Modified-Since (IMS).


activities.sugarlabs.org
------------------------

(Currently unreachable via IPv6)

Does two redirections for start page (/ -> /en-US/ -> /en-US/sugar/), 
both times with caching disabled and probably incomplete Vary header 
(only gives Accept-Encoding, nothing language-related).
Remaining pages: Not cached when using default squid settings because LM 
is not given. Does not support IMS.


api.sugarlabs.org
-----------------

Works fine. Amazingly fast. :-P


git.sugarlabs.org
-----------------

Explicitly disabled (even for static data like commits):

<<<
Cache-Control: private, max-age=0, must-revalidate
>>>

Vary not set, no LM, IMS not supported.


schools.sugarlabs.org
---------------------

Explicitly disabled:

<<<
Expires:
Cache-Control: private, pre-check=0, post-check=0, max-age=0
Pragma: no-cache
>>>
[sic]

Vary not set, no LM, IMS not supported.


download.sugarlabs.org
----------------------

Directories: Vary set, but no LM and no IMS.
Files: OK (tested using wget+squid).


lists.sugarlabs.org
-------------------

Explicitly disabled for main page:

<<<
Cache-control: no-cache
>>>

Seems fine otherwise, esp. archives.


remaining services
------------------

Not tested because I got tired.


Test method
-----------

All tests done using telnet, giving only HEAD request and Host header 
(optionally If-Modified-Since) given. => Nothing that would have matched 
Vary.
Requested the usual HTML, not images or tarballs unless explicitly 
mentioned.

CU Sascha

-- 
http://sascha.silbe.org/
http://www.infra-silbe.de/
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