I set up varnish in my site and after the set up, checked the http header for an anonymous user. This was the response:
Status: HTTP/1.1 200 OK Server: Apache/2.2.15 (CentOS)
Cache-Control: max-age=0, no-cache Content-Language: en
Link: http://www.website.com/; rel="canonical",http://www.website.com/; rel="shortlink",https://plus.google.com/u/0/b/randomnumber/randomnumber/; rel="publisher"
Vary: Accept-Encoding X-Mod-Pagespeed: 18.104.22.168-3566
Content-Type: text/html; charset=utf-8
Date: Sat, 08 Feb 2014 20:53:08 GMT
Via: 1.1 varnish Connection: close
This is what isvarnishworking.com has got to say on this:
Varnish appears to be responding at that url, but the Cache-Control header's "max-age" value is less than 1, which means that Varnish will never serve content from cache at this url.
This means that the purpose of me setting up varnish is not served. Is this correct? Varnishstat shows a hit to miss ratio of 50% which is good enough to start with:
83 Client connections accepted 230 Client requests received 21 Cache hits 49 Cache misses 210 Backend conn. success 164 Fetch with Length 1 Fetch wanted close 39 N struct sess_mem 1 N struct sess 37 N struct object 37 N struct objectcore 26 N struct objecthead 90 N struct smf 16 N large free smf 1 N struct vbe_conn 2 N worker threads 12 N worker threads created 375315 N worker threads limited 104 N overflowed work requests 1 N backends 12 N expired objects 8 N LRU moved objects 184 Objects sent with write 82 Total Sessions 230 Total Requests 160 Total pass 209 Total fetch 84600 Total header bytes 1377549 Total body bytes 8 Session Closed 223 Session Linger 224 Session herd 19641 SHM records 1662 SHM writes 1 SHM MTX contention 213 allocator requests 74 outstanding allocations 409600 bytes allocated 10439155712 bytes free 210 Backend requests made 1 N vcl total 1 N vcl available 1 N total active purges 1 N new purges added 70 HCB Lookups without lock 35 HCB Lookups with lock 35 HCB Inserts 752 Client uptime 44 Fetch no body (304)
Here is a screeshot of the admin/configure/development/performance page: