安装配置PgBouncer for PostgreSQL

PgBouncer链接池来自于PostgreSQL社区，它能够为多个数据库管理链接池，而且这些数据库能够位于不一样的PostgreSQL后端。PgBouncer会为每一种数据库用户与数据库的组合创建一个池。一个被池化的链接只能被来自于同一个用户和数据库的另外一个链接请求重用。
客户端应用不须要作软件修改，可是要链接到链接池的主机和端口而不是PostgreSQL的主机和端口。PgBouncer会建立新的数据库链接或者重用一个已有的链接。当客户端断开链接时，该链接会被返回给链接池以备重用。

一、安装pgbounce

PgBounce的安装有两种方式，源代码安装和安装rpm二进制软件包。这里使用rpm软件安装，以下：

[root@hdp06 ~]# yum -y install pgbouncer 
[root@hdp06 ~]# rpm -ql pgbouncer
/etc/logrotate.d/pgbouncer
/etc/pgbouncer
/etc/pgbouncer/mkauth.py
/etc/pgbouncer/mkauth.pyc
/etc/pgbouncer/mkauth.pyo
/etc/pgbouncer/pgbouncer.ini
/etc/sysconfig/pgbouncer
/usr/bin/pgbouncer
/usr/lib/systemd/system/pgbouncer.service
/usr/lib/tmpfiles.d/pgbouncer.conf
/usr/share/doc/pgbouncer
/usr/share/doc/pgbouncer/NEWS.rst
/usr/share/doc/pgbouncer/README.rst
/usr/share/doc/pgbouncer/pgbouncer.ini
/usr/share/doc/pgbouncer/userlist.txt
/usr/share/licenses/pgbouncer-1.9.0
/usr/share/licenses/pgbouncer-1.9.0/COPYRIGHT
/usr/share/man/man1/pgbouncer.1.gz
/usr/share/man/man5/pgbouncer.5.gz
/var/run/pgbouncer

二、配置pgbounce

编辑配置文件，修改如下内容：

[databases]
kkdb= host=192.168.120.149 port=5432 user=kkuser password=redhat
postgres= host=192.168.120.149 port=5432 user=postgres password=redhat
[pgbouncer]
logfile = /var/log/pgbouncer/pgbouncer.log
pidfile = /var/run/pgbouncer/pgbouncer.pid
listen_addr = *
listen_port = 6432
auth_type = md5
auth_file = /etc/pgbouncer/userlist.txt
admin_users = postgres,kkuser
pool_mode = session
server_reset_query = DISCARD ALL
ignore_startup_parameters = extra_float_digits
max_client_conn = 1000
default_pool_size = 200

上面的认证模式md5，因此指定认证文件的路径，并加入如下内容：

[root@hdp06 pgbouncer]# vi userlist.txt 
"postgres" "md5fe4b5cfa57349c59d9b18d6920de5f59"
"kkuser" "md5ad9501a851743f17648b943395f791e0"

其中的md5值，能够在数据库中经过md5将密码进行编码，以下：

postgres=# SELECT 'md5'||md5('redhat'||'postgres');

若是安装的是rpm二进制软件包，则使用下面的方法：

[root@hdp06 ~]# cd /etc/pgbouncer
[root@hdp06 pgbouncer]# ./mkauth.py userlist.txt "host=192.168.120.149 port=5432 dbname=kkdb user=kkuser password=redhat"
[root@hdp06 pgbouncer]# chown pgbouncer:pgbouncer userlist.txt
--或者直接查询数据库
postgres=# select usename, passwd from pg_shadow order by 1;

或者使用下面的命令直接生成，删除不须要的行便可：

postgres=# copy (select '"' || rolname|| '" "'|| coalesce(rolpassword,'')||'"' from pg_authid) to '/tmp/userlist.txt';

三、启动pgbouncer

若是经过源代码安装，只能使用非root用户启动。

[root@hdp06 pgbouncer]# systemctl enable pgbouncer
[root@hdp06 pgbouncer]# systemctl start pgbouncer
[root@hdp06 pgbouncer]# systemctl status pgbouncer
● pgbouncer.service - A lightweight connection pooler for PostgreSQL
   Loaded: loaded (/usr/lib/systemd/system/pgbouncer.service; enabled; vendor preset: disabled)
   Active: active (running) since Thu 2018-12-13 17:13:07 CST; 5s ago
  Process: 21134 ExecStart=/usr/bin/pgbouncer -d -q ${BOUNCERCONF} (code=exited, status=0/SUCCESS)
 Main PID: 21136 (pgbouncer)
   CGroup: /system.slice/pgbouncer.service
           └─21136 /usr/bin/pgbouncer -d -q /etc/pgbouncer/pgbouncer.ini

Dec 13 17:13:07 hdp06 systemd[1]: Starting A lightweight connection pooler for PostgreSQL...
Dec 13 17:13:07 hdp06 systemd[1]: PID file /var/run/pgbouncer/pgbouncer.pid not readable (yet?) after start.
Dec 13 17:13:07 hdp06 systemd[1]: Started A lightweight connection pooler for PostgreSQL.
[root@hdp06 pgbouncer]# netstat -antpl|grep 6432
tcp        0      0 0.0.0.0:6432            0.0.0.0:*               LISTEN      21136/pgbouncer     
tcp6       0      0 :::6432                 :::*                    LISTEN      21136/pgbouncer

四、测试pgbouncer

[postgres@pg07 ~]$ psql -Upostgres -dpostgres -p6432 -h192.168.120.104
Password for user postgres: 
psql (10.6)
Type "help" for help.
postgres=# \l

五、管理PgBouncer

PgBouncer有一个管理控制台，能够登陆到pgbouncer虚拟数据库来访问它。该控制台接受类SQL命令，这些命令容许用户监控、从新配置和管理PgBouncer。

[postgres@pg07 ~]$ psql -Upostgres -dpgbouncer -p6432 -h192.168.120.104
Password for user postgres: 
psql (10.6, server 1.9.0/bouncer)
Type "help" for help.

pgbouncer=# show clients;
pgbouncer=# show servers;

若是变动了pgbouncer配置文件，不用重启，直接reload下就ok。

pgbouncer=# reload;

更多pgbouncer管理，请参考官方文档。