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pgpool-II和pgpoolAdmin的使用

2022-07-06 18:38:00 【华为云】

一、简介

之前发布过几篇有关PG中主从流复制的文章：

【DB宝60】PG12高可用之1主2从流复制环境搭建及切换测试
【DB宝61】PostgreSQL使用Pgpool-II实现读写分离+负载均衡
PostgreSQL高可用之repmgr（1主2从+1witness）+Pgpool-II实现主从切换+读写分离+负载均衡
【DB宝72】pgpool-II和pgpoolAdmin的使用

有关pgpool-II的相关文档：

pgpool-II 3.2.5手册
pgpool-II-3.2.5入门教程

但是，之前的文章中没有介绍有关pgpoolAdmin的知识，这款针对pgpool开发的web界面工具，还是比较实用的。

pgpool项目还提供了一个使用PHP写的 Web管理工具，称为“pgpoolAdmin "，该Web管理工具可以以 Web界面方式实现pgpool-II 的配置。

pgpoolAdmin下载：https://pgpool.net/mediawiki/index.php/Downloads

pgpoolAdmin官方文档：https://www.pgpool.net/docs/pgpoolAdmin/index_en.html

The pgpool Administration Tool is management tool of pgpool. It is possible to monitor, start, stop pgpool and change setting for pgpool.

PgpoolAdmin是管理pgpool的WEB界面工具，可以对pgpool进行监控，启停服务，更改设置。

先来一张图：

今天我们就来介绍一下pgpool-II和pgpoolAdmin的使用。

二、环境架构

注意：
本环境中的192.168.66.35或192.168.1.35均指的是同一台宿主机。
上图中的所有环境均在该宿主机中安装。

三、快速部署1主2从流复制环境

3.1、申请主机

-- 拉取镜像docker pull postgres:12-- 创建专用网络docker network create --subnet=172.72.6.0/24 pg-network-- 创建宿主机相关映射路径mkdir -p /docker_data/pg/lhrpg64302/datamkdir -p /docker_data/pg/lhrpg64303/datamkdir -p /docker_data/pg/lhrpg64304/data-- 主库docker rm -f lhrpg64302rm -rf /docker_data/pg/lhrpg64302/datadocker run -d --name lhrpg64302 -h lhrpg64302 \   -p 64302:5432 --net=pg-network --ip 172.72.6.2 \   -v /docker_data/pg/lhrpg64302/data:/var/lib/postgresql/data \   -v /docker_data/pg/lhrpg64302/bk:/bk \   -e POSTGRES_PASSWORD=lhr \   -e TZ=Asia/Shanghai \   postgres:12-- 从库1docker rm -f lhrpg64303rm -rf /docker_data/pg/lhrpg64303/datarm -rf /docker_data/pg/lhrpg64303/bkdocker run -d --name lhrpg64303 -h lhrpg64303 \   -p 64303:5432 --net=pg-network --ip 172.72.6.3 \   -v /docker_data/pg/lhrpg64303/data:/var/lib/postgresql/data \   -v /docker_data/pg/lhrpg64303/bk:/bk \   -e POSTGRES_PASSWORD=lhr \   -e TZ=Asia/Shanghai \   postgres:12      -- 从库2docker rm -f lhrpg64304rm -rf /docker_data/pg/lhrpg64304/datarm -rf /docker_data/pg/lhrpg64304/bkdocker run -d --name lhrpg64304 -h lhrpg64304 \   -p 64304:5432 --net=pg-network --ip 172.72.6.4 \   -v /docker_data/pg/lhrpg64304/data:/var/lib/postgresql/data \   -v /docker_data/pg/lhrpg64304/bk:/bk \   -e POSTGRES_PASSWORD=lhr \   -e TZ=Asia/Shanghai \   postgres:12   -- 远程登录psql -U postgres -h 192.168.66.35 -p 64302psql -U postgres -h 192.168.66.35 -p 64303psql -U postgres -h 192.168.66.35 -p 64304

3.2、主库操作

3.2.1、主库放开防火墙

cat  << EOF > /docker_data/pg/lhrpg64302/data/pg_hba.conf# TYPE DATABASE USER ADDRESS METHODlocal     all       all                    trusthost      all       all   127.0.0.1/32     trusthost      all       all    0.0.0.0/0        md5host   replication  all    0.0.0.0/0        md5EOF

注意添加replication

3.2.2、主库配置归档

docker exec -it lhrpg64302 bash-- 该路径也需要在从库创建mkdir -p /postgresql/archivechown -R postgres.postgres /postgresql/archivecat >> /var/lib/postgresql/data/postgresql.conf <<"EOF"wal_level='replica'archive_mode='on'archive_command='test ! -f /postgresql/archive/%f && cp %p /postgresql/archive/%f'restore_command='cp /postgresql/archive/%f %p'max_wal_senders=10wal_keep_segments=256wal_sender_timeout=60sEOF-- 重启docker restart lhrpg64302-- 或：/usr/lib/postgresql/12/bin/pg_ctl restart -D /var/lib/postgresql/data/psql -U postgres -h 192.168.66.35 -p 64302select * from pg_settings where name in ('wal_level','archive_mode','archive_command');-- 切换归档select pg_switch_wal();

执行结果：

postgres=# select * from pg_settings where name in ('wal_level','archive_mode','archive_command');      name       |                             setting                              | unit |          category           |                            short_desc                             | extra_desc |  context   | vartype |       source       | min_val | max_val |         enumvals          | boot_val |                            reset_val                             |                sourcefile                | sourceline | pending_restart-----------------+------------------------------------------------------------------+------+-----------------------------+-------------------------------------------------------------------+------------+------------+---------+--------------------+---------+---------+---------------------------+----------+------------------------------------------------------------------+------------------------------------------+------------+----------------- archive_command | test ! -f /postgresql/archive/%f && cp %p /postgresql/archive/%f |      | Write-Ahead Log / Archiving | Sets the shell command that will be called to archive a WAL file. |            | sighup     | string  | configuration file |         |         |                           |          | test ! -f /postgresql/archive/%f && cp %p /postgresql/archive/%f | /var/lib/postgresql/data/postgresql.conf |        753 | f archive_mode    | on                                                               |      | Write-Ahead Log / Archiving | Allows archiving of WAL files using archive_command.              |            | postmaster | enum    | configuration file |         |         | {always,on,off}           | off      | on                                                               | /var/lib/postgresql/data/postgresql.conf |        752 | f wal_level       | replica                                                          |      | Write-Ahead Log / Settings  | Set the level of information written to the WAL.                  |            | postmaster | enum    | configuration file |         |         | {minimal,replica,logical} | replica  | replica                                                          | /var/lib/postgresql/data/postgresql.conf |        751 | f(3 rows)postgres=# select * from pg_stat_get_archiver();-[ RECORD 1 ]------+-----------------------------------------archived_count     | 8last_archived_wal  | 000000010000000000000006.00000028.backuplast_archived_time | 2021-04-22 11:42:54.049649+00failed_count       | 0last_failed_wal    |last_failed_time   |stats_reset        | 2021-04-22 11:35:55.727069+00postgres=# select pg_switch_wal();-[ RECORD 1 ]-+----------pg_switch_wal | 0/7015058postgres=# select * from pg_stat_get_archiver();-[ RECORD 1 ]------+------------------------------archived_count     | 9last_archived_wal  | 000000010000000000000007last_archived_time | 2021-04-23 01:00:30.076916+00failed_count       | 0last_failed_wal    |last_failed_time   |stats_reset        | 2021-04-22 11:35:55.727069+00-- 切换归档前root@lhrpg64302:/# ps -ef|grep postpostgres     1     0  0 01:28 ?        00:00:00 postgrespostgres    26     1  0 01:28 ?        00:00:00 postgres: checkpointer  postgres    27     1  0 01:28 ?        00:00:00 postgres: background writer  postgres    28     1  0 01:28 ?        00:00:00 postgres: walwriter  postgres    29     1  0 01:28 ?        00:00:00 postgres: autovacuum launcher  postgres    30     1  0 01:28 ?        00:00:00 postgres: archiver  postgres    31     1  0 01:28 ?        00:00:00 postgres: stats collector  postgres    32     1  0 01:28 ?        00:00:00 postgres: logical replication launcher  postgres    33     1  0 01:29 ?        00:00:00 postgres: postgres postgres 172.72.6.1(6884) idleroot        40    34  0 01:29 pts/0    00:00:00 grep postroot@lhrpg64302:/# cd /postgresql/archive/root@lhrpg64302:/postgresql/archive# ls -ltotal 0-- 切换归档postgres=# select pg_switch_wal(); pg_switch_wal--------------- 0/1645528(1 row)-- 切换归档后root@lhrpg64302:/postgresql/archive# ls -ltotal 16384-rw------- 1 postgres postgres 16777216 Apr 23 01:30 000000010000000000000001root@lhrpg64302:/postgresql/archive# ps -ef|grep post postgres     1     0  0 01:28 ?        00:00:00 postgrespostgres    26     1  0 01:28 ?        00:00:00 postgres: checkpointer  postgres    27     1  0 01:28 ?        00:00:00 postgres: background writer  postgres    28     1  0 01:28 ?        00:00:00 postgres: walwriter  postgres    29     1  0 01:28 ?        00:00:00 postgres: autovacuum launcher  postgres    30     1  0 01:28 ?        00:00:00 postgres: archiver   last was 000000010000000000000001postgres    31     1  0 01:28 ?        00:00:00 postgres: stats collector  postgres    32     1  0 01:28 ?        00:00:00 postgres: logical replication launcher  postgres    33     1  0 01:29 ?        00:00:00 postgres: postgres postgres 172.72.6.1(6884) idleroot        47    34  0 01:30 pts/0    00:00:00 grep post

参数max_wal_senders介绍：

Specifies the maximum number of concurrent connections from standby servers or streaming base backup clients (i.e., the maximum number of simultaneously running WAL sender processes). The default is zero, meaning replication is disabled. WAL sender processes count towards the total number of connections, so the parameter cannot be set higher than max_connections. This parameter can only be set at server start. wal_level must be set to archive or hot_standby to allow connections from standby servers.

也就是说，这个参数是在主机上设置的，是从机连接到主机的并发连接数之总和，所以这个参数是个正整型。默认值是0，也即默认没有流复制功能。该并发连接数从进程上看，就是各个wal sender进程数之和，可以通过ps -ef|grep senders来查看，所以该值不能超过系统的最大连接数(max_connections，该BUG在9.1.5被修复)，可以允许超过实际的流复制用户数。该参数更改需要重启DB，比如我只配了一个从机:

[[email protected] database]$ ps -ef|grep sender
postgres 21257 21247 0 20:57 ? 00:00:00 postgres: wal sender process repuser 192.25.10.71(46161) streaming 0/4018ED8
postgres 22193 20949 0 23:02 pts/0 00:00:00 grep sender

参数wal_keep_segments=256介绍

表示保留多少个WAL文件。如果源库业务较繁忙，那么应该相应的增加这个值。

在PG13中，wal_keep_segments 已经取消，改用 wal_keep_size

参数wal_sender_timeout=60s介绍

中断那些停止活动超过指定毫秒数的复制连接。这对发送服务器检测一个后备机崩溃或网络中断有用。设置为0将禁用该超时机制。这个参数只能在postgresql.conf文件中或在服务器命令行上设置。默认值是 60 秒。

3.2.3、主库创建复制用户

create role replhr login encrypted password 'lhr' replication;

创建用户需要加上replication选项。

3.3、从库操作

3.3.1、在从库对主库进行备份

这里，我们在第一个从库上进行备份即可。

docker exec -it lhrpg64303 bashmkdir -p /bkchown postgres:postgres /bksu - postgrespg_basebackup -h 172.72.6.2 -p 5432 -U replhr -l bk20210422 -F p -P -R -D /bk

执行完成后，会产生文件standby.signal，如下：

root@lhrpg64303:/# mkdir -p /bkroot@lhrpg64303:/# chown postgres:postgres /bkroot@lhrpg64303:/# root@lhrpg64303:/# su - postgrespostgres@lhrpg64303:~$ postgres@lhrpg64303:~$ pg_basebackup -h 172.72.6.2 -p 5432 -U replhr -l bk20210422 -F p -P -R -D /postgresql/pgdata Password: 24560/24560 kB (100%), 1/1 tablespacepostgres@lhrpg64303:~$ cd /postgresql/pgdata/postgres@lhrpg64303:/postgresql/pgdata$ ll-bash: ll: command not foundpostgres@lhrpg64303:/postgresql/pgdata$ ls -ltotal 116-rw------- 1 postgres postgres 3 Apr 22 10:52 PG_VERSION-rw------- 1 postgres postgres 209 Apr 22 10:52 backup_labeldrwx------ 5 postgres postgres 4096 Apr 22 10:52 basedrwx------ 2 postgres postgres 4096 Apr 22 10:52 globaldrwx------ 2 postgres postgres 4096 Apr 22 10:52 pg_commit_tsdrwx------ 2 postgres postgres 4096 Apr 22 10:52 pg_dynshmem-rw-r--r-- 1 postgres postgres 243 Apr 22 10:52 pg_hba.conf-rw------- 1 postgres postgres 1636 Apr 22 10:52 pg_ident.confdrwx------ 4 postgres postgres 4096 Apr 22 10:52 pg_logicaldrwx------ 4 postgres postgres 4096 Apr 22 10:52 pg_multixactdrwx------ 2 postgres postgres 4096 Apr 22 10:52 pg_notifydrwx------ 2 postgres postgres 4096 Apr 22 10:52 pg_replslotdrwx------ 2 postgres postgres 4096 Apr 22 10:52 pg_serialdrwx------ 2 postgres postgres 4096 Apr 22 10:52 pg_snapshotsdrwx------ 2 postgres postgres 4096 Apr 22 10:52 pg_statdrwx------ 2 postgres postgres 4096 Apr 22 10:52 pg_stat_tmpdrwx------ 2 postgres postgres 4096 Apr 22 10:52 pg_subtransdrwx------ 2 postgres postgres 4096 Apr 22 10:52 pg_tblspcdrwx------ 2 postgres postgres 4096 Apr 22 10:52 pg_twophasedrwx------ 3 postgres postgres 4096 Apr 22 10:52 pg_waldrwx------ 2 postgres postgres 4096 Apr 22 10:52 pg_xact-rw------- 1 postgres postgres 255 Apr 22 10:52 postgresql.auto.conf-rw------- 1 postgres postgres 26756 Apr 22 10:52 postgresql.conf-rw------- 1 postgres postgres 0 Apr 22 10:52 standby.signalpostgres@lhrpg64303:/postgresql/pgdata$

在PG12之前，-R备份结束之后会自动生成recovery.conf文件，用来做流复制判断主从同步的信息。但是从PG12开始，这个文件已经不需要了。只需要在参数文件postgresql.conf中配置primary_conninfo参数即可。

3.3.2、还原从库1

-- 关闭从库1，删除从库的数据文件，并且将备份文件覆盖从库的数据文件docker stop lhrpg64303rm -rf /docker_data/pg/lhrpg64303/data/*cp -r /docker_data/pg/lhrpg64303/bk/* /docker_data/pg/lhrpg64303/data/

3.3.3、还原从库2

-- 关闭从库2，删除从库的数据文件，并且将备份文件覆盖从库的数据文件docker stop lhrpg64304rm -rf /docker_data/pg/lhrpg64304/data/*cp -r /docker_data/pg/lhrpg64303/bk/* /docker_data/pg/lhrpg64304/data/

3.3.4、修改2个从库的primary_conninfo参数

-- 从库1cat >> /docker_data/pg/lhrpg64303/data/postgresql.conf <<"EOF"primary_conninfo = 'host=172.72.6.2 port=5432 user=replhr password=lhr'EOF-- 从库2cat >> /docker_data/pg/lhrpg64304/data/postgresql.conf <<"EOF"primary_conninfo = 'host=172.72.6.2 port=5432 user=replhr password=lhr'EOF

3.3.5、启动从库

docker start lhrpg64303 lhrpg64304

主库进程：

root@lhrpg64302:/# ps -ef|grep postpostgres     1     0  0 11:35 ?        00:00:00 postgrespostgres    26     1  0 11:35 ?        00:00:00 postgres: checkpointer  postgres    27     1  0 11:35 ?        00:00:00 postgres: background writer  postgres    28     1  0 11:35 ?        00:00:00 postgres: walwriter  postgres    29     1  0 11:35 ?        00:00:00 postgres: autovacuum launcher  postgres    30     1  0 11:35 ?        00:00:00 postgres: archiver   last was 000000010000000000000006.00000028.backuppostgres    31     1  0 11:35 ?        00:00:00 postgres: stats collector  postgres    32     1  0 11:35 ?        00:00:00 postgres: logical replication launcher  postgres    33     1  0 11:35 ?        00:00:00 postgres: postgres postgres 172.72.6.1(52776) idlepostgres   129     1  0 11:48 ?        00:00:00 postgres: walsender replhr 172.72.6.3(40056) streaming 0/7000148

从库进程：

root@lhrpg64303:/# ps -ef|grep postpostgres     1     0  0 11:48 ?        00:00:00 postgrespostgres    26     1  0 11:48 ?        00:00:00 postgres: startup   recovering 000000010000000000000007postgres    27     1  0 11:48 ?        00:00:00 postgres: checkpointer  postgres    28     1  0 11:48 ?        00:00:00 postgres: background writer  postgres    29     1  0 11:48 ?        00:00:00 postgres: stats collector  postgres    30     1  0 11:48 ?        00:00:00 postgres: walreceiver   streaming 0/7000148postgres    31     1  0 11:48 ?        00:00:00 postgres: postgres postgres 172.72.6.1(54413) idle

四、部署和使用pgpool-II和pgpoolAdmin工具

[root@lhrpgpool /]# systemctl enable httpdCreated symlink from /etc/systemd/system/multi-user.target.wants/httpd.service to /usr/lib/systemd/system/httpd.service.[root@lhrpgpool /]# [root@lhrpgpool /]# systemctl start httpd[root@lhrpgpool /]# systemctl status httpd● httpd.service - The Apache HTTP Server   Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled; vendor preset: disabled)   Active: active (running) since Thu 2021-06-24 15:11:58 CST; 10s ago     Docs: man:httpd(8)           man:apachectl(8) Main PID: 602 (httpd)   Status: "Total requests: 0; Current requests/sec: 0; Current traffic: 0 B/sec"   CGroup: /docker/d45b808bb68bd3fa21db1881b6fc82a1ae194abc88fcbb6b8667875d9257ac54/system.slice/httpd.service           ├─602 /usr/sbin/httpd -DFOREGROUND           ├─603 /usr/sbin/httpd -DFOREGROUND           ├─604 /usr/sbin/httpd -DFOREGROUND           ├─605 /usr/sbin/httpd -DFOREGROUND           ├─606 /usr/sbin/httpd -DFOREGROUND           └─607 /usr/sbin/httpd -DFOREGROUNDJun 24 15:11:58 lhrpgpool systemd[1]: Starting The Apache HTTP Server...Jun 24 15:11:58 lhrpgpool httpd[602]: AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using 172.17.0.2. Set the 'ServerName' directive globally to suppress this messageJun 24 15:11:58 lhrpgpool systemd[1]: Started The Apache HTTP Server.

Web登录地址：

宿主机登录：http://192.168.1.35:180/admin/login.php

用户名和密码：pgpooladmin/lhr

容器内登录：http://127.0.0.1/admin/login.php

若要容器内登陆，则需要登陆到Linux的桌面中，我们通过远程桌面登录：

用户名和密码：root/lhr

打开Firefox浏览器，输入如下地址：http://127.0.0.1/admin/login.php

也可以登陆。

登录后可以看到的界面：

每个参数有详细的说明，也可以参考：

pgpool-II 3.2.5手册
pgpool-II-3.2.5入门教程

4.4、测试pgpool-II的读写分离+负载均衡+内存查询缓存功能

4.4.1、先关闭内存查询缓存

我们先关闭内存查询缓存功能，一会再来开启这个功能。

vi /postgresql/pgpool/etc/pgpool.confmemory_cache_enabled = off

配置完成后，重新启动pgpool服务：

systemctl restart pgpool

4.4.2、测试读写分离+负载均衡

测试过程：

-- 开3个窗口，密码为lhrpsql -U postgres -h 192.168.66.35 -p 19999 -d sbtestcreate table test(id int);insert into test values(1);select * from test;show pool_nodes;show pool_backend_stats;

– 获取pgPool_II 版本信息
show pool_version;
– 查看配置文件
show pool_status;
– 获取节点信息
show pool_nodes;
– 获取pgPool-II 进程信息
show pool_processes;
– 获取pgPool-II 所有的连接池信息
show pool_pools;
– 命令执行统计信息
show pool_backend_stats;
– 健康统计信息
show pool_health_check_stats;
– 缓存统计信息
show pool_cache;

C:\Users\lhrxxt>psql -U postgres -h 192.168.66.35 -p 19999 -d sbtestPassword for user postgres:psql (13.3, server 12.2 (Debian 12.2-2.pgdg100+1))Type "help" for help.sbtest=#sbtest=# show pool_nodes; node_id |  hostname  | port | status | lb_weight |  role   | select_cnt | load_balance_node | replication_delay | replication_state | replication_sync_state | last_status_change---------+------------+------+--------+-----------+---------+------------+-------------------+-------------------+-------------------+------------------------+--------------------- 0       | 172.72.6.2 | 5432 | up     | 0.333333  | primary | 0          | false             | 0                 |                   |                        | 2021-06-24 15:38:35 1       | 172.72.6.3 | 5432 | up     | 0.333333  | standby | 0          | false             | 0                 |                   |                        | 2021-06-24 15:38:35 2       | 172.72.6.4 | 5432 | up     | 0.333333  | standby | 0          | true              | 0                 |                   |                        | 2021-06-24 15:38:35(3 rows)sbtest=# show pool_backend_stats; node_id |  hostname  | port | status |  role   | select_cnt | insert_cnt | update_cnt | delete_cnt | ddl_cnt | other_cnt | panic_cnt | fatal_cnt | error_cnt---------+------------+------+--------+---------+------------+------------+------------+------------+---------+-----------+-----------+-----------+----------- 0       | 172.72.6.2 | 5432 | up     | primary | 0          | 0          | 0          | 0          | 0       | 0         | 0         | 0         | 0 1       | 172.72.6.3 | 5432 | up     | standby | 0          | 0          | 0          | 0          | 0       | 0         | 0         | 0         | 0 2       | 172.72.6.4 | 5432 | up     | standby | 0          | 0          | 0          | 0          | 0       | 0         | 0         | 0         | 0(3 rows)sbtest=#sbtest=# create table test(id int);CREATE TABLEsbtest=# insert into test values(1);INSERT 0 1sbtest=# select * from test; id----  1(1 row)sbtest=# show pool_backend_stats; node_id |  hostname  | port | status |  role   | select_cnt | insert_cnt | update_cnt | delete_cnt | ddl_cnt | other_cnt | panic_cnt | fatal_cnt | error_cnt---------+------------+------+--------+---------+------------+------------+------------+------------+---------+-----------+-----------+-----------+----------- 0       | 172.72.6.2 | 5432 | up     | primary | 0          | 1          | 0          | 0          | 1       | 0         | 0         | 0         | 0 1       | 172.72.6.3 | 5432 | up     | standby | 0          | 0          | 0          | 0          | 0       | 0         | 0         | 0         | 0 2       | 172.72.6.4 | 5432 | up     | standby | 1          | 0          | 0          | 0          | 0       | 0         | 0         | 0         | 0(3 rows)sbtest=# select * from test; id----  1(1 row)sbtest=# select * from test; id----  1(1 row)sbtest=# show pool_backend_stats; node_id |  hostname  | port | status |  role   | select_cnt | insert_cnt | update_cnt | delete_cnt | ddl_cnt | other_cnt | panic_cnt | fatal_cnt | error_cnt---------+------------+------+--------+---------+------------+------------+------------+------------+---------+-----------+-----------+-----------+----------- 0       | 172.72.6.2 | 5432 | up     | primary | 0          | 1          | 0          | 0          | 1       | 0         | 0         | 0         | 0 1       | 172.72.6.3 | 5432 | up     | standby | 0          | 0          | 0          | 0          | 0       | 0         | 0         | 0         | 0 2       | 172.72.6.4 | 5432 | up     | standby | 3          | 0          | 0          | 0          | 0       | 0         | 0         | 0         | 0(3 rows)

使用shell来测试负载均衡：

[pgsql@lhrpgpool ~]$ for i in $(seq 1 20); do psql -U postgres -h 127.0.0.1 -p 9999 -d sbtest -c 'SELECT inet_server_addr()'; done | egrep '172.'  172.72.6.4 172.72.6.2 172.72.6.4 172.72.6.4 172.72.6.4 172.72.6.3 172.72.6.3 172.72.6.3 172.72.6.4 172.72.6.3 172.72.6.2 172.72.6.4 172.72.6.3 172.72.6.4 172.72.6.4 172.72.6.2 172.72.6.3 172.72.6.4 172.72.6.2 172.72.6.2   sbtest=# show pool_backend_stats; node_id |  hostname  | port | status |  role   | select_cnt | insert_cnt | update_cnt | delete_cnt | ddl_cnt | other_cnt | panic_cnt | fatal_cnt | error_cnt---------+------------+------+--------+---------+------------+------------+------------+------------+---------+-----------+-----------+-----------+----------- 0       | 172.72.6.2 | 5432 | up     | primary | 23         | 1          | 0          | 0          | 1       | 61        | 0         | 0         | 0 1       | 172.72.6.3 | 5432 | up     | standby | 18         | 0          | 0          | 0          | 0       | 18        | 0         | 0         | 0 2       | 172.72.6.4 | 5432 | up     | standby | 28         | 0          | 0          | 0          | 0       | 26        | 0         | 0         | 1(3 rows)

可以看到，172.72.6.2、172.72.6.3和172.72.6.4服务器是均衡的读的。

下面将参数文件/postgresql/pgpool/etc/pgpool.conf中的backend_weight0修改为0，再重新启动pgpool后进行测试：

[pgsql@lhrpgpool ~]$ for i in $(seq 1 50); do psql -U postgres -h 127.0.0.1 -p 9999 -d sbtest -c 'SELECT inet_server_addr()'; done | egrep '172.'  172.72.6.3 172.72.6.3 172.72.6.4.............. 172.72.6.3 172.72.6.3 172.72.6.3 172.72.6.4 172.72.6.4 172.72.6.4  sbtest=# show pool_backend_stats; node_id |  hostname  | port | status |  role   | select_cnt | insert_cnt | update_cnt | delete_cnt | ddl_cnt | other_cnt | panic_cnt | fatal_cnt | error_cnt---------+------------+------+--------+---------+------------+------------+------------+------------+---------+-----------+-----------+-----------+----------- 0       | 172.72.6.2 | 5432 | up     | primary | 0          | 0          | 0          | 0          | 0       | 50        | 0         | 0         | 0 1       | 172.72.6.3 | 5432 | up     | standby | 30         | 0          | 0          | 0          | 0       | 30        | 0         | 0         | 0 2       | 172.72.6.4 | 5432 | up     | standby | 20         | 0          | 0          | 0          | 0       | 20        | 0         | 0         | 0(3 rows)

可以看到，所有的读全部发送到了172.72.6.3和172.72.6.4上了。

4.4.3、开启内存查询缓存

https://www.pgpool.net/docs/latest/en/html/runtime-in-memory-query-cache.html

https://www.pgpool.net/docs/pgpool-II-3.2.5/pgpool-zh_cn.html#memqcache

你可以在任何模式中使用基于内存的查询缓存。它不同于以上的查询缓存，因为基于内存的查询缓存会快很多，因为缓存存储于内存中。另外，如果缓存事小了，你不需要重启 pgpool-II 因为相关的表已经得到更新了。

基于内存的缓存保存 SELECT 语句（以及它绑定的参数，如果 SELECT 是一个扩展的查询）以及对应的数据。如果是相同的 SELECT 语句，则直接返回缓存的值。因为不再有 SQL 分析或者到 PostgreSQL 的调用，实际上它会非常快。

其他方面，它会比较慢，因为它增加了一些负载用于缓存。另外，当一个表被更新，pgpool 自动删除相关的表的缓存。因此，在有很多更新的系统中，性能会降低。如果 cache_hit_ratio 低于 70%（可以查询show pool_cache;），建议你关闭基于内存的缓存。

修改参数memory_cache_enabled=on 就会开启查询缓存功能。另外，需要设置memqcache_oiddir路径，创建目录/var/log/pgpool/oiddir，并赋权。

vi /postgresql/pgpool/etc/pgpool.confmemory_cache_enabled = onmkdir -p /var/log/pgpool/oiddirchown -R pgsql.pgsql /var/log/pgpool/oiddir

配置完成后，重新启动pgpool服务：

systemctl restart pgpool

接下来，测试缓存功能：

sbtest=# show pool_backend_stats; node_id |  hostname  | port | status |  role   | select_cnt | insert_cnt | update_cnt | delete_cnt | ddl_cnt | other_cnt | panic_cnt | fatal_cnt | error_cnt---------+------------+------+--------+---------+------------+------------+------------+------------+---------+-----------+-----------+-----------+----------- 0       | 172.72.6.2 | 5432 | up     | primary | 0          | 0          | 0          | 0          | 0       | 0         | 0         | 0         | 0 1       | 172.72.6.3 | 5432 | up     | standby | 0          | 0          | 0          | 0          | 0       | 0         | 0         | 0         | 0 2       | 172.72.6.4 | 5432 | up     | standby | 0          | 0          | 0          | 0          | 0       | 0         | 0         | 0         | 0(3 rows)[pgsql@lhrpgpool ~]$ for i in $(seq 1 50); do psql -U postgres -h 127.0.0.1 -p 9999 -d sbtest -c 'SELECT * from test'; done | egrep 'row' | wc -l50sbtest=# show pool_backend_stats; node_id |  hostname  | port | status |  role   | select_cnt | insert_cnt | update_cnt | delete_cnt | ddl_cnt | other_cnt | panic_cnt | fatal_cnt | error_cnt---------+------------+------+--------+---------+------------+------------+------------+------------+---------+-----------+-----------+-----------+----------- 0       | 172.72.6.2 | 5432 | up     | primary | 0          | 0          | 0          | 0          | 0       | 50        | 0         | 0         | 0 1       | 172.72.6.3 | 5432 | up     | standby | 0          | 0          | 0          | 0          | 0       | 22        | 0         | 0         | 0 2       | 172.72.6.4 | 5432 | up     | standby | 1          | 0          | 0          | 0          | 0       | 28        | 0         | 0         | 0(3 rows)sbtest=# delete from test;DELETE 1sbtest=# select * from test; id----(0 rows)sbtest=# show pool_health_check_stats; node_id |  hostname  | port | status |  role   | last_status_change  | total_count | success_count | fail_count | skip_count | retry_count | average_retry_count | max_retry_count | max_duration | min_duration | average_duration |  last_health_check  | last_successful_health_check | last_skip_health_check | last_failed_health_check---------+------------+------+--------+---------+---------------------+-------------+---------------+------------+------------+-------------+---------------------+-----------------+--------------+--------------+------------------+---------------------+------------------------------+------------------------+-------------------------- 0       | 172.72.6.2 | 5432 | up     | primary | 2021-06-24 16:20:08 | 57          | 57            | 0          | 0          | 0           | 0.000000            | 0               | 8            | 7            | 7.035088         | 2021-06-24 16:29:29 | 2021-06-24 16:29:29          |                        | 1       | 172.72.6.3 | 5432 | up     | standby | 2021-06-24 16:20:08 | 57          | 57            | 0          | 0          | 0           | 0.000000            | 0               | 7            | 7            | 7.000000         | 2021-06-24 16:29:29 | 2021-06-24 16:29:29          |                        | 2       | 172.72.6.4 | 5432 | up     | standby | 2021-06-24 16:20:08 | 57          | 57            | 0          | 0          | 0           | 0.000000            | 0               | 8            | 7            | 7.017544         | 2021-06-24 16:29:29 | 2021-06-24 16:29:29          |                        |(3 rows)