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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Thank you, Gordon for your reply.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">In your patch I see that you are setting the isolation_level to REPEATABLE_READ. We are trying to change the isolation level to READ_COMMITTED.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I like to refer you to this performance article[1] that determines that READ_COMMITTED is usually better than REPEATABLE_READ.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">In addition, maybe an additional reason for your slowness is that you do it when you get the connection – so you do an extra DB command that sets the isolation
level.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">My patch is changing the default isolation level for all connections upfront.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">[1]
<a href="https://www.percona.com/blog/2015/01/14/mysql-performance-implications-of-innodb-isolation-modes/">
https://www.percona.com/blog/2015/01/14/mysql-performance-implications-of-innodb-isolation-modes/</a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext"> gord chung [mailto:gord@live.ca]
<br>
<b>Sent:</b> Tuesday, December 08, 2015 2:50 PM<br>
<b>To:</b> openstack-dev@lists.openstack.org<br>
<b>Subject:</b> Re: [openstack-dev] [oslo.db][sqlalchemy][mistral] Configuring default transaction isolation level<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-bottom:12.0pt">we had this in ceilometer events. you can see it here:
<a href="https://github.com/openstack/ceilometer/commit/898cd3d036c4358aa16f7b3e2028365dc9829213">
https://github.com/openstack/ceilometer/commit/898cd3d036c4358aa16f7b3e2028365dc9829213</a><br>
<br>
note, that patch is removing it because it slowed everything way down because of locking. if you can avoid it, avoid it.<o:p></o:p></p>
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<p class="MsoNormal">On 08/12/2015 7:28 AM, Renat Akhmerov wrote:<o:p></o:p></p>
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<p class="MsoNormal">Hi, <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Moshe, thanks a lot for bringing this up. I remember I tried to find a way to change isolation level per connection but also was unable to do that.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">An advice from oslo team would be very helpful.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Renat Akhmerov<o:p></o:p></p>
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<p class="MsoNormal">@ Mirantis Inc.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On 08 Dec 2015, at 13:41, ELISHA, Moshe (Moshe) <<a href="mailto:moshe.elisha@alcatel-lucent.com">moshe.elisha@alcatel-lucent.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">Hi,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">We at Mistral want to move from the default transaction isolation level of REPEATABLE READ to READ COMMITTED as part of a bugfix[1].<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">I did not find a way to pass the isolation level to sqlachemy using oslo.db and the current solution is to use monkey-patching[2] that adds the “isolation_level” property.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">Is there currently a better way to set the default isolation level?<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">If not – I will create a BP for it.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">Thanks.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">[1]<span class="apple-converted-space"> </span><a href="https://review.openstack.org/#/c/253819">https://review.openstack.org/#/c/253819</a><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">[2]<span class="apple-converted-space"> </span><a href="https://review.openstack.org/#/c/253819/11/mistral/db/sqlalchemy/base.py">https://review.openstack.org/#/c/253819/11/mistral/db/sqlalchemy/base.py</a><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
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<pre>-- <o:p></o:p></pre>
<pre>gord<o:p></o:p></pre>
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