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<p class="MsoNormal">Hi Matt,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I’m working on the patch fd6cfc upstreaming, which tries to address the stale RPC message issue when DHCP agent restarting up.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The patch was in good shape <a href="https://review.openstack.org/609463/">
https://review.openstack.org/609463/</a> whereas the neutron community was questioning about the exact failure modes of this issue. The DHCP agent will have a full sync after the agent restarting up (<a href="https://github.com/openstack/neutron/blob/master/neutron/agent/dhcp/agent.py#L195">https://github.com/openstack/neutron/blob/master/neutron/agent/dhcp/agent.py#L195</a>),
what kind of corner cases and negative behaviors could happen even w/ this full sync?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Based on the commit message, I tried to reproduce this issue w/ the following steps:<o:p></o:p></p>
<p class="MsoListParagraph" style="margin-left:.25in;text-indent:-.25in;mso-list:l0 level1 lfo1">
<![if !supportLists]><span style="mso-list:Ignore">1.<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>schedule network1 to agent1.<o:p></o:p></p>
<p class="MsoListParagraph" style="margin-left:.25in;text-indent:-.25in;mso-list:l0 level1 lfo1">
<![if !supportLists]><span style="mso-list:Ignore">2.<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>turn down agent1 at almost the same time.<o:p></o:p></p>
<p class="MsoListParagraph" style="margin-left:.25in;text-indent:-.25in;mso-list:l0 level1 lfo1">
<![if !supportLists]><span style="mso-list:Ignore">3.<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>network1 is rescheduled to agent2 after finding that agent1 is dead.<o:p></o:p></p>
<p class="MsoListParagraph" style="margin-left:.25in;text-indent:-.25in;mso-list:l0 level1 lfo1">
<![if !supportLists]><span style="mso-list:Ignore">4.<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>turn up agent1, expecting stale RPC messages to be received by agent1 so that both agent1 and agent2 are servicing network1.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">However, I can only meet the described failure mode by sending another scheduling operation (network1->agent1) after step 2) is done. For the others, they seem to work as expected.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Would you please kindly help provide more details about the failure pattern of this issue and/or the reproduction steps? Thanks a lot.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">BR,<o:p></o:p></p>
<p class="MsoNormal">Kailun<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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