I have no idea why backend is sick

[Abraham Cruz Sustaita]

I have 8 servers, 7 of them are working as they supposed to be working.
However, I have app02, and it is not working. The first problem I noticed
was it was reporting errors even when I change the error reporting to off.
The second problem, and the one that is give me troubles, is that after I
reboot the server, it is not working. I have this in the log:

varnishlog | grep app02
    0 Backend_health - app02 Still healthy 4--X-R- 3 3 5 0.000488 0.000000
HTTP/1.1 301 Moved Permanently
    5 BackendOpen  b app02 192.168.11.42 48452 192.168.11.32 80
    5 BackendReuse b app02
    4 Backend      c 5 old app02
    4 ObjHeader    c b_n: app02
    4 TxHeader     c b_n: app02
   37 BackendOpen  b app02 192.168.11.42 48460 192.168.11.32 80
   37 BackendReuse b app02
    5 BackendReuse b app02
   20 Backend      c 5 old app02
   20 ObjHeader    c b_n: app02
   20 TxHeader     c b_n: app02
   28 Backend      c 37 old app02
   28 ObjHeader    c b_n: app02
   28 TxHeader     c b_n: app02
    0 Backend_health - app02 Went sick 4--X-R- 2 3 5 0.000722 0.000000
HTTP/1.1 301 Moved Permanently
    5 BackendReuse b app02
   68 Backend      c 5 old app02
   68 ObjHeader    c b_n: app02
   68 TxHeader     c b_n: app02
   37 BackendReuse b app02
   75 Backend      c 37 old app02
   75 ObjHeader    c b_n: app02
   75 TxHeader     c b_n: app02
  123 TxHeader     c b_n: app02
  259 TxHeader     c b_n: app02
  187 TxHeader     c b_n: app02
    0 Backend_health - app02 Still sick 4--X-R- 1 3 5 0.000520 0.000000
HTTP/1.1 301 Moved Permanently
   67 TxHeader     c b_n: app02
    0 Backend_health - app02 Still sick 4--X-R- 0 3 5 0.000503 0.000000
HTTP/1.1 301 Moved Permanently

But the problem is that the server is working ok. If I do wget app02 from
varnish, it returns what it is supposed to return! But varnish says that it
went sick... Is there anyway I can trace this?

I have modified my hosts file in order to point www.domain.com to app02 so
I can do wget www.domain.com (www.domain.com is the domain I have in that
server), and it response as it supposed:

wget --server-response --spider www.domain.com
Spider mode enabled. Check if remote file exists.
--2012-07-18 23:53:20--  http://www.domain.com/
Resolving www.domain.com... 192.168.11.32
Connecting to www.domain.com|192.168.11.32|:80... connected.
HTTP request sent, awaiting response...
  HTTP/1.1 200 OK
  Date: Wed, 18 Jul 2012 23:53:20 GMT
  Server: Apache/2.2.22 (Fedora)
  X-Powered-By: PHP/5.4.4
  Set-Cookie: sessionToken=a73cdcde6439423231f19f7ce6870ae7; expires=Thu,
18-Jul-2013 23:53:21 GMT; path=/; domain=.domain.com
  Set-Cookie: sessionToken=46560b800baa0ee9cf0f7eeea8dc1add; expires=Thu,
18-Jul-2013 23:53:21 GMT; path=/; domain=.domain.com
  Set-Cookie: sessionToken=8bfa42f1782db58726ebdc500ede7705; expires=Thu,
18-Jul-2013 23:53:21 GMT; path=/; domain=.domain.com
  Vary: Accept-Encoding
  Cache-Control: no-store, no-cache, must-revalidate, max-age=0
  Pragma: no-cache
  Keep-Alive: timeout=15, max=100
  Connection: Keep-Alive
  Content-Type: text/html; charset=iso-8859-1
Length: unspecified [text/html]
Remote file exists and could contain further links,
but recursion is disabled -- not retrieving.
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