Too many 503 backend errors

[Robert Shilston]

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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