<html><head></head><body>Isn't that the case with all primary-standby type clusters?<br><br><div class="gmail_quote">On 8 May 2021 15.39.26 EEST, MichaelDBA <MichaelDBA@sqlexec.com> wrote:<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<pre class="k9mail">Wow, first I heard of that --> "We do not recommend 2-node pgpool <br>configuration. "<br><br><br><br>Tatsuo Ishii wrote on 5/5/2021 5:17 PM:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #729fcf; padding-left: 1ex;"><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #ad7fa8; padding-left: 1ex;"> Dear Tatsuo,<br><br> thank you for your answer.<br><br> I do recognize the dangers of a split-brain scenario.<br><br> With a 2-node setup, however, it is possible to configure PgPool to<br> have the VIP on one node while the other node is down (unreachable),<br> even though it may very well be a split-brain situation:<br><br> Node B loses connection to Node A. Neither of them has the quorum (in<br> fact there can never be a quorum in a 2-node cluster), still Node B<br> will have the VIP as well as Node A.<br><br> With that risk in mind, why can we not have such an option for<br> clusters with more than 2 nodes?<br></blockquote> We do not recommend 2-node pgpool configuration. The option for 2-node<br> which your are referring to is enable_consensus_with_half_votes (the<br> default is off). It was created just for a compromise because there<br> have been already too many 2-node users.<br><br><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #ad7fa8; padding-left: 1ex;"> Regards,<br><br> tamas<br><br><br> 2021. 05. 05. 14:04 keltezéssel, Tatsuo Ishii írta:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #8ae234; padding-left: 1ex;"><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #fcaf3e; padding-left: 1ex;"> Dear all,<br><br> I have fairly common 3-node cluster, with each node running a PgPool<br> and a PostreSQL instance.<br><br> I have set up priorities so that:<br> - when all 3 nodes are up, the 1st node is gonna have the VIP,<br> - when the 1st node is down, the 2nd node is gonna have the VIP, and<br> - when both the 1st and the 2nd nodes are down, then the 3rd node<br> should get the VIP.<br><br> My problem is that when only 1 node is up, the VIP is not brought up,<br> because there is no quorum.<br> How can I get PgPool to bring up the VIP to the only remaining node,<br></blockquote> There's no way to do that.<br><br><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #fcaf3e; padding-left: 1ex;">which still could and should serve requests?<br></blockquote> No, because it's dangerous. Think about a split brain scenario: node A<br> loses connection to node B and c. In this case node A loses the<br> quorum, while node B and C have the quorum and will keep the VIP. If<br> we allow the VIP to node A, there are 2 VIPs are up. We surely want to<br> avoid it.<br><br> Best regards,<br> --<br> Tatsuo Ishii<br> SRA OSS, Inc. Japan<br> English: <a href="http://www.sraoss.co.jp/index_en.php">http://www.sraoss.co.jp/index_en.php</a><br> Japanese:http://www.sraoss.co.jp<hr> pgpool-general mailing list<br> pgpool-general@pgpool.net<br> <a href="http://www.pgpool.net/mailman/listinfo/pgpool-general">http://www.pgpool.net/mailman/listinfo/pgpool-general</a><br></blockquote></blockquote><hr>pgpool-general mailing list<br>pgpool-general@pgpool.net<br><a href="http://www.pgpool.net/mailman/listinfo/pgpool-general">http://www.pgpool.net/mailman/listinfo/pgpool-general</a><br></blockquote><hr>pgpool-general mailing list<br>pgpool-general@pgpool.net<br><a href="http://www.pgpool.net/mailman/listinfo/pgpool-general">http://www.pgpool.net/mailman/listinfo/pgpool-general</a><br></pre></blockquote></div></body></html>