<div dir="ltr">We have been recently having intermittent problems with our pgpool setup that causes service outages for usually 5-20 minutes, and we cannot figure out what the problem is.<br><br><div><img src="cid:ii_kf5flu6j1" alt="server_stats.jpg" width="189" height="542"><br></div><a href="https://i.imgur.com/JodLFhl.jpg" target="_blank">https://i.imgur.com/JodLFhl.jpg</a><div><br><br>As you can see from the graph, incoming TCP connections jump up very high (usually up to num_init_connections * backlog multiplier) and then we start seeing the listen queue socket overflows. We have somaxxcon set quite high on the server 8000 and the num_init_connections * listen_backlog_multiplier is 150 * 10<br><br>pgpool doesn't show any errors, but doesn't seem to be working correctly. If I run netstat -n, I see a lot of ESTABLISHED connections (a lot more than num_init_connetions * max_pool) from the PHP front-end web servers to pgpool. I see the correct number (num_init_connections * backlog multiplier) of ESTABLISHED connections from pgpool to the back-end postgres servers, and there is no major load on these servers. Also, I can see there are available connections on the back-end postgres servers.<br><br>This problem is more likely to happen during a period of high volume, but we do also see it happen during quieter periods. The pgpools logs don't show any errors or issues.<br>If we restart pgpool, everything seems to go back to normal and working correctly again.<br><br>Attached is our configuration, and we would love to get some assistance on this.<br>We are running pgpool v4.1.3 on Ubuntu 16.04.3<br><br>
I have attached the netstat output for when the server is operating correctly, and when it is erroring and overflowing. 10.0.0.17 and 10.0.0.18 are our front-end PHP servers. 10.0.0.10 and 127.0.0.1 are our back-end postgres servers.
<br><br>If anyone can help, I would much appreciate it.<br><br>Thanks<br></div></div>