Too many 503 backend errors

[Anand Shah]

It works for 6 out of 10 requests. I have also found that varnish
polls backend before sending a GET request. Since i never received any
request on my apache server for this dropped requests i am in doubt as
if what makes varnish feel the backend is in unhealthy state.

Is there any way that i can troubleshoot?



Anand

On 12/22/10, Robert Shilston <rtshilston at gmail.com> wrote:
> Anand,
>
> Check that vcl_recv is actually setting a backend.  It might be that there's
> a route through the VCL that doesn't cause a backend to be specified.
>
> Rob
>
> On 22 Dec 2010, at 08:39, Anand Shah wrote:
>
>> I immediately fired a test call using CURL which indicated me a
>> tcp_miss and i also got the response from origin.
>>
>> So backend was working and in healthy state.
>>
>>
>>
>> [root at mymachine ~]# curl --head --header host:imads.mydomain.com
>> "http://localhost//0/OasDefault/IIPM_CPL_Nov10_B3_MW/iipm_winter02_300x600_10dec_03.gif"
>>  HTTP/1.1 200 OK
>>  Last-Modified: Thu, 02 Dec 2010 12:19:14 GMT
>>  P3P: CP="NON NID PSAa PSDa OUR IND UNI COM NAV
>> STA",policyref="/w3c/p3p.xml"
>>  Content-Type: image/gif
>>  cache-control: max-age=604800
>>  Content-Length: 4150
>>  Date: Wed, 22 Dec 2010 06:39:26 GMT
>>  Connection: keep-alive
>>  H-Served-By: mymachine
>>  Server: mydomain/2.0.6
>>  X-Cache: TCP_MISS
>>
>>  [root at mymachine ~]# curl --head --header host:imads.mydomain.com
>> "http://localhost//0/OasDefault/IIPM_CPL_Nov10_B3_MW/iipm_winter02_300x600_10dec_03.gif"
>>  HTTP/1.1 200 OK
>>  Last-Modified: Thu, 02 Dec 2010 12:19:14 GMT
>>  P3P: CP="NON NID PSAa PSDa OUR IND UNI COM NAV
>> STA",policyref="/w3c/p3p.xml"
>>  Content-Type: image/gif
>>  cache-control: max-age=604800
>>  Content-Length: 4150
>>  Date: Wed, 22 Dec 2010 06:39:33 GMT
>>  Connection: keep-alive
>>  H-Served-By: mymachine
>>  Server: mydomain/2.0.6
>>  X-Cache: TCP_HIT
>>
>>
>>
>>
>> Regards,
>>   Anand
>>
>> On Wed, Dec 22, 2010 at 12:42:24PM +0530, Anand Shah wrote:
>>> I am running varnish on 64 bit Centos. Getting too many 503 errors
>>> recently and i tried debugging it with some help from Forums on
>>> mailinglist.
>>
>>> VARNISHLOGS:
>>>
>>>  180 VCL_call     c miss fetch
>>>  180 FetchError   c no backend connection
>>>  180 VCL_call     c error deliver
>>
>> In my experience, "no backend connection" indicates that whatever
>> backend was selected to handle this request was unavailable due to the
>> health check/probe returning an error.
>>
>> What was the backend health at the time? You can use the 'debug.health'
>> command in the CLI to view health information, or
>>
>>  varnishlog -i Backend_health
>>
>> to see the results of the health checks as they occur. If a backend is
>> marked as 'sick' then Varnish won't send any requests to it, since
>> it's unlikely to help the situation.
>>
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>>
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>
>