solution for Active/Passive Backend

[Guillaume Quintard]

Hi,

You will have to define a probe, otherwise Varnish will consider the
backend to be healthy by default. You would then be able to manually make
it sick, but for automatic health, you need probing.

Kind regards,
-- 
Guillaume Quintard


On Sat, Jul 4, 2020 at 8:47 AM hamidreza hosseini <hrhosseini at hotmail.com>
wrote:

> 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>
> 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
> https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc
>
>
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