solution for Active/Passive Backend

hamidreza hosseini hrhosseini at
Sat Jul 4 15:47:18 UTC 2020

Thanks for your answer,
I read yor blog post, you wrote there that fallback director will check the health status of the servers and it will choose one of them that is healthy(First one) , so by this explanation i dont need to define the prob for my backends to understand that my backends are healthy or not, is it true?
is this config file enough for my purpose?
import directors;

backend alpha1 { .host = ""; }
backend alpha2 { .host = ""; }
backend err    { .host = ""; }

sub vcl_int {
    new alpha_rr = directors.round_robin();

    new alpha_fb = directors.fallback();
Best Regards
From: Guillaume Quintard <guillaume at>
Sent: Saturday, July 4, 2020 8:11 AM
To: hamidreza hosseini <hrhosseini at>
Cc: varnish-misc at <varnish-misc at>
Subject: Re: solution for Active/Passive Backend


You want to use probes and the fallback director.

Relevant documentation:
to define a probe:
to attach it to backends:
the fallback director:

i also wrote these blog posts a long time ago, but they are still valid:

The first one goes through probes, and the second one explores directors, including the fallback one.

Hope that helps

Guillaume Quintard

On Sat, Jul 4, 2020 at 7:14 AM hamidreza hosseini <hrhosseini at<mailto:hrhosseini at>> wrote:
I want to have 2 or 3 backends in the Varnish config file but just one of them workes as an active backend and whenever my active backend failed , the second backend become active and respond the requests. (In other hand, I dont want to have two backend for responding clients and just one of them works at the same time, and it check the health status of my active backend , whenever it is was unhealthy , varnish switch to the second or third backend.)
Best Regards.
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