solution for Active/Passive Backend

[hamidreza hosseini]

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 = "192.168.0.101"; }
backend alpha2 { .host = "192.168.0.201"; }
backend err    { .host = "192.168.0.150"; }

sub vcl_int {
    new alpha_rr = directors.round_robin();
    alpha_rr.add_backend(alpha1);
    alpha_rr.add_backend(alpha2);

    new alpha_fb = directors.fallback();
    alpha_fb.add_backend(alpha_rr.backend());
    alpha_fb.add_backend(err);
}
"
Best Regards
________________________________
From: Guillaume Quintard <guillaume at varnish-software.com>
Sent: Saturday, July 4, 2020 8:11 AM
To: hamidreza hosseini <hrhosseini at hotmail.com>
Cc: varnish-misc at varnish-cache.org <varnish-misc at varnish-cache.org>
Subject: Re: solution for Active/Passive Backend

Hi,

You want to use probes and the fallback director.

Relevant documentation:
to define a probe:https://varnish-cache.org/docs/6.4/reference/vcl.html?highlight=probe#probes
to attach it to backends: https://varnish-cache.org/docs/6.4/reference/vcl.html?highlight=probe#backend-definition
the fallback director: https://varnish-cache.org/docs/6.4/reference/vmod_directors.html?highlight=fallback#directors-fallback

i also wrote these blog posts a long time ago, but they are still valid:
https://info.varnish-software.com/blog/backends-load-balancing
https://info.varnish-software.com/blog/backends-load-balancing-part-2

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 hotmail.com<mailto:hrhosseini at hotmail.com>> wrote:
Hi,
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.
_______________________________________________
varnish-misc mailing list
varnish-misc at varnish-cache.org<mailto:varnish-misc at varnish-cache.org>
https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://www.varnish-cache.org/lists/pipermail/varnish-misc/attachments/20200704/5fc96bd0/attachment.html>