Cache miss for same page from different browsers

[David Murphy]

Thanks Martin

Yes, sorry that was just a typo (should have been 'tobots.txt' not 'text.txt'), but the details of the issue are correct.

Laurence kindly suggested it was a Vary: Accept-Encoding header issue and after following http://varnish-cache.org/wiki/FAQ/Compression the issue is now sorted.

Best, David
________________________________________
From: Martin Boer [martin.boer at netclever.nl]
Sent: 15 March 2010 07:17
To: David Murphy
Cc: varnish-misc at varnish-cache.org
Subject: Re: Cache miss for same page from different browsers

Hello David,

I'm afraid you need some coffee;

David Murphy wrote:
> Hello
>
> I've been testing a simple txt page to confirm that when viewed by one browser (and cached in Varnish) that it is delivered as a Varnish cached file to a second browser.
>
> My test is very simple: I have both Chrome and Firefox browsers open, and am trying access http:127.0.0.1/test.txt
>
> 1. Restart varnishd + apache2
> 2. Clear cookies/browser cache in obth browsers
> 3. Visit http:127.0.0.1/test.txt in Chrome and confirm via varnishtop -b -i TxURL that /text.txt has been cached
>
> ===
> list length 2
>      1.00 TxURL          /robots.txt
>      1.00 TxURL          /favicon.ico
> ===
>
>

test.txt hasn't been cached here but robots.txt is.
I'm afraid you misread.


> 4.Then visit same URL in Firefox
>
> Now, the header results from (4) when I reach /test.txt (but already cached in Varnish) is
>
> X-Cacheable   YES
> Date  Sat, 13 Mar 2010 11:33:22 GMT
> X-Varnish     1385957804
> Age   43
> Via   1.1 varnish
> X-Cache       MISS
>
> Then if I hit refresh on this page (not force reload) I get
>
> X-Cacheable   YES
> Date  Sat, 13 Mar 2010 11:34:15 GMT
> X-Varnish     1385957805
> Age   43
> Via   1.1 varnish
> X-Cache       HIT
>
> Note that there is only a single X-Varnish request number (1385957805) even though we get X-Cache: HIT
>
> If I refresh again I get  the same results, but if I force reload (shift + reload) I get:
>
> X-Cacheable   YES
> Date  Sat, 13 Mar 2010 11:36:28 GMT
> X-Varnish     1385957807 1385957804
> Age   187
> Via   1.1 varnish
> Connection    keep-alive
> X-Cache       HIT
>
> My VCL file is below:
>
> ===============
>
>  GNU nano 2.0.9                        File: /etc/varnish/default.vcl
>
> backend default {
> .host = "127.0.0.1";
> .port = "8080";
> .connect_timeout = 600s;
> .first_byte_timeout = 600s;
> .between_bytes_timeout = 600s;
> }
>
> sub vcl_recv {
> unset req.http.cookie;
> lookup;
> }
>
> sub vcl_fetch {
> unset obj.http.Set-Cookie;
>
>     # Varnish determined the object was not cacheable
>     if (!obj.cacheable) {
>         set obj.http.X-Cacheable = "NO:Not Cacheable";
>
>     # You don't wish to cache content for logged in users
>     } elsif(req.http.Cookie ~"(UserID|_session)") {
>         set obj.http.X-Cacheable = "NO:Got Session";
>         pass;
>
>     # You are respecting the Cache-Control=private header from the backend
>     } elsif ( obj.http.Cache-Control ~ "private") {
>         set obj.http.X-Cacheable = "NO:Cache-Control=private";
>         pass;
>
>     # You are extending the lifetime of the object artificially
>     } elsif ( obj.ttl < 1s ) {
>         set obj.ttl   = 5s;
>         set obj.grace = 5s;
>         set obj.http.X-Cacheable = "YES:FORCED";
>
>     # Varnish determined the object was cacheable
>     } else {
>         set obj.http.X-Cacheable = "YES";
>     }
>
>     deliver;
> }
>
> ===============
>
>
> Thanks for any assistance.
>
> David
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