基于Pgpool-II的PostgreSQL集群


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

1.安装CentOS7的yum源。

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

2.安装支持PostgreSQL10版本的pgpool-II

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$ yum install pgpool-II-pg10
$ yum install pgpool-II-pg10-debuginfo
$ yum install pgpool-II-pg10-devel
$ yum install pgpool-II-pg10-extensions

3.服务开机启动

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$ systemctl enable pgpool.service

4.启动/停止服务

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$ 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
在这里插入图片描述

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

架构图
在这里插入图片描述
配置系统环境
配置程序运行的用户和组为 postgres

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#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

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#"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

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#"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

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#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

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$ 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

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$ 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

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$ 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

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

编辑内容如下

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# - 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

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# - 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：

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$ 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。

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$ 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 [email protected]
#master
$ ssh [email protected]

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。

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$ 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

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$ systemctl start postgresql-10.service

分别启动各节点Pgpool-II服务

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$ systemctl start pgpool.service

集群状态
用vip登录集群，查看状态

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$ 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

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#获取192.168.1.3可见节点数
$ pcp_node_count -h 192.168.1.3 -p 9898 -U postgres
Password:
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#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

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#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。

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$ 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。

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