基于PgpoolII的PostgreSQL集群安装与配置教程

安装Pgpool-II

Pgpool-II 是一个位于 PostgreSQL服务器和 PostgreSQL数据库客户端之间的中间件，Pgpool-II提供了连接池（Connection Pooling）、复制（Replication）、负载均衡（Load Balancing）、缓存（In Memory Query Cache）、看门狗（Watchdog）、超出限制链接（Limiting Exceeding Connections）等功能，可以基于这些特性来搭建PostgreSQL高可用集群。

yum安装

官方参考地址

Yum Repository

Installation from RPM

安装CentOS7的yum源。

$ yum install http://www.pgpool.net/yum/rpms/4.0/redhat/rhel-7-x86_64/pgpool-II-release-4.0-1.noarch.rpm

安装支持PostgreSQL10版本的pgpool-II

$ yum install pgpool-II-pg10

$ yum install pgpool-II-pg10-debuginfo

$ yum install pgpool-II-pg10-devel

$ yum install pgpool-II-pg10-extensions

服务开机启动

$ systemctl enable pgpool.service

启动/停止服务

$ systemctl start pgpool.service

$ systemctl stop pgpool.service

配置Pgpool-II

参考文章



pgpool-II的安装及使用

PGPool-II+PG流复制实现HA主备切换

实例准备

role ip PostgreSQL Pgpool-II port

master 192.168.1.3 10.9 4.0.5 5432

slave 192.168.1.2 10.9 4.0.5 5432

vip 192.168.1.100 – – –

watchdog端口9000，pcp端口9898，psql服务连接端口9999

架构图

Pgpool-II集群

配置系统环境

配置程序运行的用户和组为 postgres

创建或修改目录权限

$ chown -R postgres.postgres /etc/pgpool-II

$ mkdir /var/run/pgpool/

$ chown postgres.postgres /var/run/pgpool/

修改pgpool运行用户和组为postgres

$ vi /usr/lib/systemd/system/pgpool.service

User=postgres

Group=postgres

配置认证方式

配置pool_hba.conf，要么都是trust，要么都是md5验证方式，这里采用了md5验证方式如下设置

“local” is for Unix domain socket connections only

local all all md5

IPv4 local connections:

host all all 127.0.0.1/32 md5

host all all ::1/128 md5

host all all 0.0.0.0/0 md5

配置pg_hba.conf，认证方式保持一致

“local” is for Unix domain socket connections only

local all all md5

IPv4 local connections:

host all all 127.0.0.1/32 md5

host all all 0.0.0.0/0 md5

IPv6 local connections:

host all all ::1/128 md5

非必要可选步骤，为了集群可扩展性，可以将复制的认证条件放宽

Allow replication connections from localhost, by a user with the
replication privilege.

local replication all md5

host replication all 127.0.0.1/32 md5

host replication all ::1/128 md5

host replication all 192.168.1.0/24 md5

配置pcp

pcp.conf 配置用于pgpool自己登陆管理使用的，一些操作pgpool的工具会要求提供密码等，配置如下

配置用户名密码

$ pg_md5 postgres

e8a48653851e28c69d0506508fb27fc5

$ vi pcp.conf

USERID:MD5PASSWD

postgres:e8a48653851e28c69d0506508fb27fc5

添加pg数据库用户密码

在pgpool中添加pg数据库的用户名和密码，数据库登录用户是postgres，这里输入登录密码

$ pg_md5 -p -m -u postgres pool_passwd

password:

输入密码后，会生成一个pool_passwd文件

$ cat pool_passwd

postgres:md53175bce1d3201d16594cebf9d7eb3f9d

配置系统命令权限

$ chmod +s /sbin/ifconfig

$ chmod +s /sbin/ip

$ chmod +s /sbin/ifup

$ chmod +s /bin/ping

$ chmod +s /sbin/arping

配置 pgpool.conf

primary

$ cp pgpool.conf.sample-stream pgpool.conf

编辑内容如下

- pgpool Connection Settings -

listen_addresses = ‘*’

port = 9999

- pgpool Communication Manager Connection Settings -

pcp_listen_addresses = ‘*’

pcp_port = 9898

- Backend Connection Settings -

backend_hostname0 = ‘192.168.1.3’

backend_port0 = 5432

backend_weight0 = 1

backend_data_directory0 = ‘/var/lib/pgsql/10/data’

backend_flag0 = ‘ALLOW_TO_FAILOVER’

backend_hostname1 = ‘192.168.1.2’

backend_port1 = 5432

backend_weight1 = 1

backend_data_directory1 = ‘/var/lib/pgsql/10/data’

backend_flag1 = ‘ALLOW_TO_FAILOVER’

- Authentication -

enable_pool_hba = on

pool_passwd = ‘pool_passwd’

authentication_timeout = 60

FILE LOCATIONS

pid_file_name = ‘/var/run/pgpool/pgpool.pid’

CONNECTION POOLING

connection_cache = on

REPLICATION MODE

replication_mode = off

LOAD BALANCING MODE

load_balance_mode = on

MASTER/SLAVE MODE

master_slave_mode = on

master_slave_sub_mode = ‘stream’

- Streaming -

sr_check_period = 5

sr_check_user = ‘repuser’

sr_check_password = ‘repuser’

sr_check_database = ‘postgres’

HEALTH CHECK

health_check_period = 10

health_check_timeout = 10

health_check_user = ‘postgres’

health_check_password = ‘postgres’

health_check_database = ‘postgres’

FAILOVER AND FAILBACK

failover_command = ‘/var/lib/pgsql/10/failover_stream.sh %H’

WATCHDOG

use_watchdog = on

wd_hostname = ‘192.168.1.3’

wd_port = 9000

delegate_IP = ‘192.168.1.100’

if_cmd_path = ‘/sbin’

if_up_cmd = ‘ifconfig eth0:0 inet _IP_ netmask 255.255.255.0’

if_down_cmd = ‘ifconfig eth0:0 down’

– heartbeat mode –

heartbeat_destination0 = ‘192.168.1.2’

heartbeat_device0 = ‘eth0’

- Other pgpool Connection Settings -

other_pgpool_hostname0 = ‘192.168.1.2’

other_pgpool_port0 = 9999

other_wd_port0 = 9000

standby

编辑内容如下

- pgpool Connection Settings -

listen_addresses = ‘*’

port = 9999

- pgpool Communication Manager Connection Settings -

pcp_listen_addresses = ‘*’

pcp_port = 9898

- Backend Connection Settings -

backend_hostname0 = ‘192.168.1.3’

backend_port0 = 5432

backend_weight0 = 1

backend_data_directory0 = ‘/var/lib/pgsql/10/data’

backend_flag0 = ‘ALLOW_TO_FAILOVER’

backend_hostname1 = ‘192.168.1.2’

backend_port1 = 5432

backend_weight1 = 1

backend_data_directory1 = ‘/var/lib/pgsql/10/data’

backend_flag1 = ‘ALLOW_TO_FAILOVER’

- Authentication -

enable_pool_hba = on

pool_passwd = ‘pool_passwd’

authentication_timeout = 60

FILE LOCATIONS

pid_file_name = ‘/var/run/pgpool/pgpool.pid’

CONNECTION POOLING

connection_cache = on

REPLICATION MODE

replication_mode = off

LOAD BALANCING MODE

load_balance_mode = on

MASTER/SLAVE MODE

master_slave_mode = on

master_slave_sub_mode = ‘stream’

- Streaming -

sr_check_period = 5

sr_check_user = ‘repuser’

sr_check_password = ‘repuser’

sr_check_database = ‘postgres’

HEALTH CHECK

health_check_period = 10

health_check_timeout = 10

health_check_user = ‘postgres’

health_check_password = ‘postgres’

health_check_database = ‘postgres’

FAILOVER AND FAILBACK

failover_command = ‘/var/lib/pgsql/10/failover_stream.sh %H’

WATCHDOG

use_watchdog = on

wd_hostname = ‘192.168.1.2’

wd_port = 9000

delegate_IP = ‘192.168.1.100’

if_cmd_path = ‘/sbin’

if_up_cmd = ‘ifconfig eth0:0 inet _IP_ netmask 255.255.255.0’

if_down_cmd = ‘ifconfig eth0:0 down’

– heartbeat mode –

heartbeat_destination0 = ‘192.168.1.3’

heartbeat_device0 = ‘eth0’

- Other pgpool Connection Settings -

other_pgpool_hostname0 = ‘192.168.1.3’

other_pgpool_port0 = 9999

other_wd_port0 = 9000

failover_stream.sh

配置failover_stream.sh脚本，内容如下：

$ pwd

/var/lib/pgsql/10

$ touch failover_stream.sh

$ chmod u+x failover_stream.sh

$ cat failover_stream.sh

#! /bin/sh

Failover command for streaming replication.
Arguments: $1: new master hostname.

new_master=$1

trigger_command="/usr/bin/pg_ctl promote -D /var/lib/pgsql/10/data"

Prompte standby database.

/usr/bin/ssh -T $new_master $trigger_command

exit 0;

设置主机互信

配置ssh秘钥，分别在master、slave上生成ssh密钥对，并设置主机互信。

$ ssh-keygen -t rsa -b 1024

$ cd ~/.ssh

$ pwd

/var/lib/pgsql/.ssh

$ touch authorized_keys

$ chmod 600 authorized_keys

将master公钥id_rsa.pub内容拷贝到salve认证文件authorized_keys，同理将slave公钥id_rsa.pub内容拷贝到master认证文件authorized_keys
测试主机互信
salve

$ ssh postgres@192.168.1.3

master

$ ssh postgres@192.168.1.2

如果这个脚本的执行目标是本地，并且ssh本地登陆没有设置免秘钥，那么这个脚本会一直卡在输入密码的阶段，这时候主备自动切换过程就阻塞了。如果 pgpool和 postgresql在同一台机器部署，需要添加本地登陆免秘钥。

$ pwd

/var/lib/pgsql

$ cd .ssh/

$ ls

authorized_keys id_rsa id_rsa.pub

$ cat id_rsa.pub >> authorized_keys

启动集群

分别启动master、slave的PostgreSQL服务

$ systemctl start postgresql-10.service

分别启动各节点Pgpool-II服务

$ systemctl start pgpool.service

集群状态

用vip登录集群，查看状态

$ psql -p 9999 -h 192.168.1.100 -U postgres

Password for user postgres:

psql (10.9)

Type “help” for help.

postgres=# show pool_nodes;

node_id | hostname | port | status | lb_weight | role | select_cnt | load_balance_node | replication_delay | last_status_change

---------±--------------±-----±-------±----------±--------±-----------±------------------±------------------±--------------------

0 | 192.168.1.3 | 5432 | up | 0.500000 | primary | 5 | true | 0 | 2019-08-08 16:11:26

1 | 192.168.1.2 | 5432 | up | 0.500000 | standby | 3 | false | 0 | 2019-08-08 16:13:14

(2 rows)

至此，基于 Pgpool-II 中间件的 PostgreSQL 集群搭建完成。

PCP命令

获取节点数

获取192.168.1.3可见节点数

$ pcp_node_count -h 192.168.1.3 -p 9898 -U postgres

Password:

2

获取192.168.1.2可见节点数

$ pcp_node_count -h 192.168.1.2 -p 9898 -U postgres

Password:

2

获取节点信息

查看节点0信息

$ pcp_node_info -h 192.168.1.3 -p 9898 -U postgres 0

Password:

192.168.1.3 5432 2 0.500000 up primary 0 2019-08-08 16:11:26

查看节点1信息

$ pcp_node_info -h 192.168.1.3 -p 9898 -U postgres 1

Password:

192.168.1.2 5432 2 0.500000 up standby 0 2019-08-08 16:13:14

$

从pgpool-II中脱离一个节点

该命令将节点slave从pgpool-II中脱离。一般如果需要维护某个数据库节点、或不希望pgpool-II将连接分发到该节点时，需要将该节点从pgpool-II中用该命令脱离。

$ pcp_detach_node -h 192.168.1.100 -p 9898 -U postgres -n 1

为pgpool-II关联一个节点

该命令将节点slave关联到pgpool-II中。当维护结束，或新添加一个节点后，可以将节点添加到pgpool-II。

另外，如果该节点由于主机或数据库故障导致检测到数据库为启动时，即使后期服务器重新修复、数据库手工启动，也需要执行attach操作。同时需要注意从两个节点上观察是否节点都已经attach。

$ pcp_attach_node -h 192.168.1.100 -p 9898 -U postgres -n 1