<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Dec 21, 2016 at 12:09 AM, David Sisk -X (<span id="gmail-13900ff0-0a54-4890-bfa4-12f1837a2434" class="gmail-GINGER_SOFTWARE_mark">dsisk</span> - TEKSYSTEMS INC at Cisco) <span dir="ltr">&lt;<a href="mailto:dsisk@cisco.com" target="_blank">dsisk@cisco.com</a>&gt;</span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">





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<p class="MsoNormal"><a name="m_-5996073559596526301__MailEndCompose"><span style="font-size:11pt;font-family:calibri,sans-serif;color:rgb(31,73,125)">I believe this is unquestionably a valid concern, but I believe there is a way to configure around it (those who know watchdog better
 will provide details, I’m sure). However, there’s still the problem that, having only one primary, if the <span id="gmail-1a76e508-7903-4d55-b201-d82b4ff4f10b" class="gmail-GINGER_SOFTWARE_mark">corp</span> link is down, half of the app can’t see across regions to a primary database<span id="gmail-0c2e3bc8-de29-4f72-8f93-5d1316a310f6" class="gmail-GINGER_SOFTWARE_mark">…</span>so you have a 50% or so outage instead of a full outage.</span></a></p></div></div></blockquote><div><br></div><div>The watchdog in Pgpool-II 3.5 and onward ensures the presence of a quorum for selecting the Master Pgpool-II node, And if the Pgpool-II watchdog cluster has an odd number of nodes then it is very unlikely that Watchdog will go in the split-brain.</div><div>But the other part of the problem is a little hard to work around in this situation. I.e  in case of the network partitioning (when the link between East and West is not working) how to handle the failover in the region which does not have the Primary PostgreSQL server.</div><div><br></div><div>Best regards!</div><div>Muhammad Usama</div><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div lang="EN-US"><div class="gmail-m_-5996073559596526301WordSection1"><p class="MsoNormal"><a name="m_-5996073559596526301__MailEndCompose"><span style="font-size:11pt;font-family:calibri,sans-serif;color:rgb(31,73,125)">
<u></u><u></u></span></a></p>
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<p class="MsoNormal"><span><span style="font-size:11pt;font-family:calibri,sans-serif;color:rgb(31,73,125)">A</span></span></p></div></div></blockquote><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div lang="EN-US"><div class="gmail-m_-5996073559596526301WordSection1"><p class="MsoNormal"><span><span style="font-size:11pt;font-family:calibri,sans-serif;color:rgb(31,73,125)">gain, I’d take a close look at Postgres-BDR<span id="gmail-7f6b0684-0f39-452f-b196-bb3cf59c17b6" class="gmail-GINGER_SOFTWARE_mark">…</span>this is exactly the types of scenarios that it’s designed to handle.
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<p class="MsoNormal"><span><span style="font-size:11pt;font-family:calibri,sans-serif;color:rgb(31,73,125)">Best of luck!<u></u><u></u></span></span></p>
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<p class="MsoNormal"><span><b><span style="font-size:8.5pt;font-family:arial,sans-serif;color:rgb(102,102,102)">David Sisk</span></b></span><span><span style="font-size:8.5pt;font-family:arial,sans-serif;color:rgb(102,102,102)"><u></u><u></u></span></span></p>
<p class="MsoNormal"><span><span style="font-size:8.5pt;font-family:arial,sans-serif;color:rgb(102,102,102)">Engineer - Software<u></u><u></u></span></span></p>
<p class="MsoNormal"><span></span><a href="mailto:dsisk@cisco.com" target="_blank"><span><span style="font-size:8.5pt;font-family:arial,sans-serif;color:rgb(102,102,102);text-decoration:none">dsisk@cisco.com</span></span></a><span><span style="font-size:11pt;font-family:calibri,sans-serif;color:rgb(31,73,125)"><u></u><u></u></span></span></p>
<p class="MsoNormal"><span><span style="font-size:8.5pt;font-family:arial,sans-serif;color:rgb(102,102,102)">Tel:
<u></u><u></u></span></span></p>
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<p class="MsoNormal"><span><b><span style="font-size:8.5pt;font-family:arial,sans-serif;color:rgb(102,102,102)">Cisco Systems, Inc.<u></u><u></u></span></b></span></p>
<p class="MsoNormal"><span><span style="font-size:8.5pt;font-family:arial,sans-serif;color:rgb(102,102,102)">7025-6 Kit Creek <span id="gmail-c40a4e2a-4659-4740-a919-fc71a93303c5" class="gmail-GINGER_SOFTWARE_mark">Road PO</span> Box 14987<br>
RESEARCH TRIANGLE PARK<br>
27709-4987<br>
United States<br>
<a href="http://cisco.com" target="_blank">cisco.com</a><u></u><u></u></span></span></p>
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<p class="MsoNormal"><span><span style="font-size:7.5pt;font-family:arial,sans-serif;color:rgb(0,153,0)"><img border="0" width="18" height="19" style="width: 0.1875in; height: 0.1979in;" id="gmail-m_-5996073559596526301Picture_x0020_3" src="cid:image004.png@01D25ACA.B8B0E4E0" alt="http://www.cisco.com/assets/swa/img/thinkbeforeyouprint.gif">Think
 before you print.<u></u><u></u></span></span></p>
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<p class="MsoNormal"><b><span style="font-size:11pt;font-family:calibri,sans-serif">From:</span></b><span style="font-size:11pt;font-family:calibri,sans-serif"> <a href="mailto:pgpool-general-bounces@pgpool.net" target="_blank">pgpool-general-bounces@pgpool.<wbr>net</a> [mailto:<a href="mailto:pgpool-general-bounces@pgpool.net" target="_blank">pgpool-general-<wbr>bounces@pgpool.net</a>]
<b>On Behalf Of </b>Yates, James C. -ND<br>
<b>Sent:</b> Tuesday, December 20, 2016 12:25 PM<br>
<b>To:</b> Muhammad Usama &lt;<a href="mailto:m.usama@gmail.com" target="_blank">m.usama@gmail.com</a>&gt;<br>
<b>Cc:</b> Muhammad Usama &lt;<a href="mailto:muhammad.usama@enterprisedb.com" target="_blank">muhammad.usama@enterprisedb.<wbr>com</a>&gt;; <a href="mailto:pgpool-general@pgpool.net" target="_blank">pgpool-general@pgpool.net</a><br>
<b>Subject:</b> [<span id="gmail-6de74a9b-6ab2-489a-a5e0-b15799bdda29" class="gmail-GINGER_SOFTWARE_mark">pgpool</span>-general: 5186] Re: Architecture Questions<u></u><u></u></span></p>
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<p class="MsoNormal">What I’m concerned about is the corporate network link between the AWS regions going down and PgPool doing a failover.  Then I could have the East and West region both think they have a master and doing updates/inserts on each.  Then when
 the link comes back up, my databases are out of sync and I could lose data. <u></u><u></u></p>
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<p class="MsoNormal">On Dec 20, 2016, at 6:27 AM, Muhammad Usama &lt;<a href="mailto:m.usama@gmail.com" target="_blank">m.usama@gmail.com</a>&gt; wrote:<u></u><u></u></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:helvetica,sans-serif">Hi</span>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:helvetica,sans-serif">Can you please explain a little more about your concerns of the split-brain situation you want to avoid?<u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:helvetica,sans-serif">As far as I understand from the architecture diagram the proposed deployment consists of four PostgreSQL servers (Two in each AWS availability zone) and the Pgpool-II servers
 in front of each PostgreSQL. And the Application servers can connect to any of the four available Pgpool-II, So this seems like an active-active Pgpool-II configuration. Which means you would not be using the floating-IP (delegate IP) with the Pgpool-II.<u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:helvetica,sans-serif">So if this is correct and you are not planing to use the floating IP and master-standby configuration of Pgpool-II, What worries you about the split-brain?<u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:helvetica,sans-serif">Thanks<u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:helvetica,sans-serif">Best regards<u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:helvetica,sans-serif">Muhammad Usama<u></u><u></u></span></p>
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