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<span style="color:black;font-size:12pt;font-family:Calibri,Arial,Helvetica,sans-serif">Hi,</span><br>
<div style="color:black;font-size:12pt;font-family:Calibri,Arial,Helvetica,sans-serif">
Thanks to you and all varnish team for such answers that helped me alot,</div>
<div style="color:black;font-size:12pt;font-family:Calibri,Arial,Helvetica,sans-serif">
I read the default varnish cache configuration again: <br>
</div>
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<a href="https://github.com/varnishcache/varnish-cache/blob/6.0/bin/varnishd/builtin.vcl" target="_blank" rel="noopener noreferrer" data-auth="NotApplicable" data-linkindex="0">https://github.com/varnishcache/varnish-cache/blob/6.0/bin/varnishd/builtin.vcl</a></div>
<div style="color:black;font-size:12pt;font-family:Calibri,Arial,Helvetica,sans-serif">
and find out vcl_hash as follow:</div>
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<br>
</div>
<div style="color:black;font-size:12pt;font-family:Calibri,Arial,Helvetica,sans-serif">
```</div>
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<td><span>sub</span> <span>vcl_hash</span> {</td>
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<td><span>hash_data</span>(<span>req.url</span>);</td>
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<td><span>if</span> (<span>req.http.host</span>) {</td>
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<td><span>hash_data</span>(<span>req.http.host</span>);</td>
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</tbody>
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<td>} <span>else</span> {</td>
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</tbody>
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<td><span>hash_data</span>(<span>server.ip</span>);</td>
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<td>}</td>
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<td><span>return</span> (<span>lookup</span>);</td>
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<td>}</td>
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<br>
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```</div>
<div style="color:black;font-size:12pt;font-family:Calibri,Arial,Helvetica,sans-serif">
So, if I change vcl_hash like following , would it be enough for my purpose?(I mean caching the same object from different backends just once with roundrobin directive !:)</div>
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<br>
</div>
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```</div>
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<br>
</div>
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sub vcl_hash {
<div> hash_data(req.url);</div>
<div> return (lookup);</div>
<span>}</span><br>
</div>
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<td><br>
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```</div>
<div style="color:black;font-size:12pt;font-family:Calibri,Arial,Helvetica,sans-serif">
<br>
</div>
<div style="color:black;font-size:12pt;font-family:Calibri,Arial,Helvetica,sans-serif">
By this config I told varnish just cache the content based on the 'req.url' not 'req.http.host' therefore with the same content but different backend varnish would cache once(If I want to use round robin directive instead of shard directive ), Is this true?
what bad consequences may it cause in the future by this configuration?</div>
<br>
</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> varnish-misc <varnish-misc-bounces+hrhosseini=hotmail.com@varnish-cache.org> on behalf of Hamidreza Hosseini <hrhosseini@hotmail.com><br>
<b>Sent:</b> Sunday, August 1, 2021 4:17 AM<br>
<b>To:</b> varnish-misc@varnish-cache.org <varnish-misc@varnish-cache.org><br>
<b>Subject:</b> Best practice for caching scenario with different backend servers but same content</font>
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Hi,<br>
I want to use varnish in my scenario as cache service, I have about 10 http servers that serve Hls fragments as the backend servers and about 5 varnish servers for caching purpose, the problem comes in when I use round-robin director for backend servers in
varnish,</div>
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if a varnish for specific file requests to one backend server and for the same file but to another backend server it would cache that file again because of different Host headers ! so my solution is using fallback director instead of round-robin as follow:</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<br>
```</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
In varnish-1:
<div> new hls_cluster = directors.fallback();</div>
<div> hls_cluster.add_backend(b1());</div>
<div> hls_cluster.add_backend(b2()); </div>
<div> hls_cluster.add_backend(b3()); </div>
<div> hls_cluster.add_backend(b4()); </div>
<div> hls_cluster.add_backend(b5()); </div>
<div> hls_cluster.add_backend(b6()); </div>
<div> hls_cluster.add_backend(b7()); </div>
<div> hls_cluster.add_backend(b8()); </div>
<div> hls_cluster.add_backend(b9()); </div>
<div> hls_cluster.add_backend(b10());</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div>In varnish-2:</div>
<div> new hls_cluster = directors.fallback();</div>
<div> hls_cluster.add_backend(b10());</div>
<div> hls_cluster.add_backend(b1());</div>
<div> hls_cluster.add_backend(b2()); </div>
<div> hls_cluster.add_backend(b3()); </div>
<div> hls_cluster.add_backend(b4()); </div>
<div> hls_cluster.add_backend(b5()); </div>
<div> hls_cluster.add_backend(b6()); </div>
<div> hls_cluster.add_backend(b7()); </div>
<div> hls_cluster.add_backend(b8()); </div>
<div> hls_cluster.add_backend(b9()); </div>
<div><br>
</div>
<div><br>
</div>
<div>In varnish-3:</div>
<div> new hls_cluster = directors.fallback();</div>
<div> hls_cluster.add_backend(b9()); </div>
<div> hls_cluster.add_backend(b1());</div>
<div> hls_cluster.add_backend(b2()); </div>
<div> hls_cluster.add_backend(b3()); </div>
<div> hls_cluster.add_backend(b4()); </div>
<div> hls_cluster.add_backend(b5()); </div>
<div> hls_cluster.add_backend(b6()); </div>
<div> hls_cluster.add_backend(b7()); </div>
<div> hls_cluster.add_backend(b8()); </div>
<div> hls_cluster.add_backend(b10());</div>
<div><br>
</div>
<span></span>```<br>
But I think this is not the best solution, because there is no load balancing despite, I used different backend for the first argument of fallback directive,<br>
What is varnish recommendation for this scenario?</div>
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