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<p>All that makes sense. Do you have any concerns/benchmarks
regarding performance after migration? Have you tried migrating
your data in some POC and measure the difference in some subset of
functionality?</p>
<p>Just to give more context. The reason I am asking is that in
Candlepin, we always have had Postgres as a datastore. Some
performance challenges that we have been facing:</p>
<ul>
<li>The sheer amount of data on one node makes and the amount of
time necessary to migrate when changing schema<br>
</li>
<li>Transaction lock waits - which, at occasion, can stop client
requests and bring down the service<br>
</li>
<li>Transaction deadlocks <br>
</li>
</ul>
<p>With every new functionality I sometimes think about a
possibility to use some NoSQL to make it horizontally scalable. So
it would be interesting to hear that Mongo didn't deliver the
performance in Pulp's case.<br>
</p>
<div class="moz-cite-prefix">On 09/13/2016 03:11 PM, Michael Hrivnak
wrote:<br>
</div>
<blockquote
cite="mid:CAHLG0FCPVf4WXCjQK6rDgi1m_oBJSyPOV1B0m_NvXVBFVpLgtQ@mail.gmail.com"
type="cite">
<div dir="ltr">We have a thread here about a lot of the 3.0 stack
choices, although it seems to skip past the assumption that
we're moving to postgres:
<div><br>
</div>
<div><a moz-do-not-send="true"
href="https://www.redhat.com/archives/pulp-list/2016-May/msg00042.html">https://www.redhat.com/archives/pulp-list/2016-May/msg00042.html</a><br>
</div>
<div><br>
</div>
<div>I can't quickly find another summary of why, so I'll
describe the highlights here:</div>
<div><br>
</div>
<div>- Pulp has highly relational data. The core use case is
managing the relationships between content and repositories.
Using a relational DB makes that a lot easier.</div>
<div>- A schemaless DB makes it easy to do writes, but you have
to be very careful when doing reads that the your software is
prepared for whatever data structure comes out. If you want to
enforce a schema, it has to be done in software. It's doable,
but requires great care.</div>
<div>- Transactions!</div>
<div>- The HA story with mongodb is more complex than most
people realize (certainly more complex than we expected). To
get real HA with data safety, you have to do a lot of the work
in your own software.</div>
<div><br>
</div>
<div>MongoDB is great at what it does and a good fit for some
use cases, but we learned that it's not the best fit for Pulp.</div>
<div><br>
</div>
<div>Michael</div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Tue, Sep 13, 2016 at 3:21 AM, Filip
Nguyen <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:fnguyen@redhat.com" target="_blank">fnguyen@redhat.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">I heard
that Pulp is switching from Mongo to Postgre. Just out of
curiosity, I would like to learn more about the reasons why
you decided to go this direction. Is there any
document/email thread about it?<br>
<br>
______________________________<wbr>_________________<br>
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<a moz-do-not-send="true" href="mailto:Pulp-dev@redhat.com"
target="_blank">Pulp-dev@redhat.com</a><br>
<a moz-do-not-send="true"
href="https://www.redhat.com/mailman/listinfo/pulp-dev"
rel="noreferrer" target="_blank">https://www.redhat.com/mailman<wbr>/listinfo/pulp-dev</a><br>
</blockquote>
</div>
<br>
</div>
</blockquote>
<br>
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