Varnish 503 Service unavailable error

[Paras Fadte]

Hi,

Sometimes I receive 503 service unavailable error even though there
are 4 backends . This would mean that all the backends are unavailable
at a given time  which I don't think is the case . What could be done
to resolve this ? Following are the probe settings.

.probe = {
            .url = "/check.gif";
            .timeout = 500 ms;
            .interval = 1s;
            .window = 6;
            .threshold = 4;
         }


I have tried setting the "first_byte_timeout" value to 300 but still
sometimes receive the 503 error . Should I increase the
"connect_timeout" value ? would that help ? Its default value is 0.4
seconds

Thank you.

-Paras