<html><body><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; color: #000000"><div>Hi, we enabled connections and disconnections log. There are about total 56 connections, 42 of them are from an unique user, half to a db and another half to another db, so I think we need at least 21 connections cached for this application.</div><div>In this moment we have num_init_children=110 and max_pool=4 , should we increase max_pool to be at least 21?</div><div> <!--StartFragment--><span style="color: #000000; font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;" data-mce-style="color: #000000; font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">child_life_time and connection_life_time are set to zero.</span></div><div>Thank you.</div><div><br></div><hr id="zwchr" data-marker="__DIVIDER__"><div data-marker="__HEADERS__"><b>Da: </b>"Bo Peng" <pengbo@sraoss.co.jp><br><b>A: </b>"fmazzi" <fmazzi@comune.genova.it><br><b>Cc: </b>"pgpool-general" <pgpool-general@pgpool.net><br><b>Inviato: </b>Mercoledì, 30 giugno 2021 5:20:41<br><b>Oggetto: </b>Re: [pgpool-general: 7601] Problems with response time<br></div><div><br></div><div data-marker="__QUOTED_TEXT__">Hello,<br><br>On Tue, 29 Jun 2021 15:22:51 +0200 (CEST)<br>Francesco Mazzi <fmazzi@comune.genova.it> wrote:<br><br>> Hello, we have two instances of pgpool 4.2.2, one leader and one stand by, in front of a postgresql cluster of 3 nodes (one read/write and two read only), version 12. <br>> We noticed a strange behaviour about connection response time, both with active and standby pgpool: sometimes response time (database connection) suddenly changes from about 0,02s to about 5s and then it comes back to 0,02s. CPU load on server remains very low. <br>> We raised num_init_children to 110 but nothing changed. In this moment database it isn't very used, so why there are these low response times? <br><br>> We noticed a strange behaviour about connection response time, both with active and standby pgpool: sometimes response time (database connection) suddenly changes from about 0,02s to about 5s and then it comes back to 0,02s. CPU load on server remains very low. <br>> We raised num_init_children to 110 but nothing changed. In this moment database it isn't very used, so why there are these low response times? <br><br>The difference in database connection response time may be caused by the effect of connection cache.<br>Creating a new connection to PostgreSQL takes longer than reusing the cached connections.<br><br>In the following cases, Pgpool-II creates new connections to PostgreSQL:<br><br>- The connections to the specified database has not been created yet.<br>- If the number of cached connections exceeds specified max_pool, <br> the oldest connection will be discarded, then Pgpool-II use that slot for a new connection.<br>- Duo to the settings of child_life_time, connection_life_time, <br> the cached connections are terminated.<br><br>To figure out the cause, you can check pgpool logs if it is a new connection to PostgreSQL.<br><br>-- <br>Bo Peng <pengbo@sraoss.co.jp><br>SRA OSS, Inc. Japan<br>http://www.sraoss.co.jp/<br></div></div></body></html>