PostgreSQL流复制实现HA主备切换
环境说明和主机规划
| 操作系统 | 主机名 | 主机 | 角色 | 端口 |
|---|---|---|---|---|
| CentOS 7 | master | 10.0.0.11 | PG-Master | 54321 |
| CentOS 7 | slave | 10.0.0.12 | PG-Slave | 54321 |
| CentOS 7 | pool | 10.0.0.13 | pgpool | 54321 |
基础环境配置（所有主机操作）
配置HOSTS
echo -e "10.0.0.11 master\n10.0.0.12 slave\n10.0.0.13 pool" >> /etc/hosts # 执行一次即可
配置统一的时间（若已配置，请忽略）
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yum install -y ntpdate && ntpdate ntp1.aliyun.com
echo -e "# sync time from ntp1.aliyun.com\n5 * * * * /usr/sbin/ntpdate ntp1.aliyun.com > /dev/null 2>&1
" >> /var/spool/cron/root # 写入定时任务，执行一次即可
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创建postgres用户
useradd postgres && echo "your_password" | passwd --stdin postgres
配置免密钥登陆
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su - postgres
ssh-keygen -t rsa -f /home/postgres/.ssh/id_rsa -P ""
cd ~/.ssh/
ssh-copy-id postgres@master # 三台主机执行
scp authorized_keys postgres@slave:~/.ssh # 只在master主机执行
scp authorized_keys postgres@pool:~/.ssh # 只在master主机执行
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安装Postgresql数据库（PG9.6）
yum install -y https://download.postgresql.org/pub/repos/yum/9.6/redhat/rhel-7-x86_64/pgdg-centos96-9.6-3.noarch.rpm
yum install -y postgresql96-server postgresql96-contrib postgresql96 postgresql96-libs
创建统一的目录结构
mkdir /data1/pg_{data,bin,logs} -p
chown -R postgres.postgres /data1/
修改系统变量
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vi /etc/profile #增加以下内容
export PGHOME=/usr/pgsql-9.6/
export PGDATA=/data1/pg_data
export PGPORT=54321
export PATH=$PATH:$PGHOME/bin
# 生效
source /etc/profile
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PostgreSQL流复制结构（master和slave主机操作）
master主机操作
初始化系统
/usr/pgsql-9.6/bin/postgresql96-setup initdb
vi /usr/lib/systemd/system/postgresql-9.6.service
修改postgresql-9.6.service
内容如下:
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# Include the default config:
.include /usr/lib/systemd/system/postgresql-9.6.service
[Service]
Environment=PGDATA=/data1/pg_data
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重启PG服务
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systemctl daemon-reload
su - postgres -c '/usr/pgsql-9.6/bin/initdb -D /data1/pg_data'
systemctl restart postgresql-9.6
systemctl enable postgresql-9.6.service
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修改系统配置（以下用postgres用户操作）
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cp /data1/pg_data/pg_hba.conf{,.bak}
cat >/data1/pg_data/pg_hba.conf<<EOF
local all all trust
host all all 10.0.0.11/32 trust
host all all 10.0.0.12/32 trust
host all all 0.0.0.0/0 md5
host all all ::1/128 trust
host replication stream_replication 0.0.0.0/0 md5
EOF
#host replication stream_replication 0.0.0.0/0 md5 为流复制用户
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64G
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cp /data1/pg_data/postgresql.conf{,.bak}
cat >/data1/pg_data/postgresql.conf<<EOF
listen_addresses = '*'
port = 54321
max_connections = 256
shared_buffers = 16GB
effective_cache_size = 48GB
work_mem = 64MB
maintenance_work_mem = 2GB
min_wal_size = 2GB
max_wal_size = 4GB
checkpoint_completion_target = 0.9
wal_buffers = 16MB
default_statistics_target = 100
wal_level = hot_standby
wal_log_hints = on
max_wal_senders = 1
hot_standby = on
logging_collector = on
log_directory = 'pg_log'
EOF
#操作完记得重启 pg_ctl restart
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128G
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listen_addresses = '*'
port = 54321
max_connections = 256
shared_buffers = 32GB
effective_cache_size = 96GB
work_mem = 128MB
maintenance_work_mem = 2GB
min_wal_size = 2GB
max_wal_size = 4GB
checkpoint_completion_target = 0.9
wal_buffers = 16MB
default_statistics_target = 100
wal_level = hot_standby
wal_log_hints = on
max_wal_senders = 1
hot_standby = on
logging_collector = on
log_directory = 'pg_log'
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在主库中创建流复制用户(stream_replication)和PGPool用户(srcheck)
CREATE USER stream_replication replication LOGIN CONNECTION LIMIT 5 ENCRYPTED PASSWORD 'your_password';
CREATE USER srcheck replication LOGIN CONNECTION LIMIT 5 ENCRYPTED PASSWORD 'your_password';
修改主库pg_hba.conf文件（已操作见cat >/data1/pg_data/pg_hba.conf<<EOF）
host replication stream_replication 0.0.0.0/0 md5
slave主机操作
初始化系统
/usr/pgsql-9.6/bin/postgresql96-setup initdb
vi /usr/lib/systemd/system/postgresql-9.6.service
修改postgresql-9.6.service
内容如下:
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# Include the default config:
.include /usr/lib/systemd/system/postgresql-9.6.service
[Service]
Environment=PGDATA=/data1/pg_data
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重启PG服务
systemctl daemon-reload
基础备份复制到备库服务器
rm -rf /data1/pg_data # 如果没有重要数据可操作，主要为同步主库路径
su - postgres -c 'pg_basebackup -D $PGDATA --format=p -h master -p 54321 -U stream_replication -W'
修改备库配置信息
cp $PGHOME/share/recovery.conf.sample $PGDATA/recovery.conf
vi $PGDATA/recovery.conf
增加以下内容
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standby_mode='on'
primary_conninfo = 'host=master port=54321 user=stream_replication password=your_password'
restore_command = ''
recovery_target_timeline = 'latest'
# 重启PG服务
systemctl restart postgresql-9.6
systemctl enable postgresql-9.6.service
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验证
主节点执行
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create table test (id int4, create_time timestamp(0) without time zone);
insert into test values (1, now());
select * from test;
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备节点执行
select * from test;
其他查询
进入测试数据库test，主库上执行如下命令返回f，备库上返回t。 select pg_is_in_recovery();
执行如下命令查看快照，它返回主库记录点、备库记录点；主库每增加一条写入，记录点的值就会加1。
select txid_current_snapshot();
执行如下命令可以查看主备同步状态。
select * from pg_stat_replication;
字段state显示的同步状态有：startup（连接中）、catchup（同步中）、streaming（同步）；字段sync_state显示的模式有：async（异步）、sync（同步）、potential（虽然现在是异步模式，但是有可能升级到同步模式）。
主备切换
假设主库崩溃了，备库如何从只读状态切换为读写状态呢？只要把备库的postgresql.conf中hot_standby修改为off，并且删除recovery.conf，然后重启库就可以提供服务了。
PGPool2（pool主机操作）
安装PGPool2
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yum install -y http://www.pgpool.net/yum/rpms/3.6/redhat/rhel-7-x86_64/pgpool-II-release-3.6-1.noarch.rpm
yum -y install pgpool-II-pg96 pgpool-II-pg96-debuginfo pgpool-II-pg96-devel pgpool-II-pg96-extensions
systemctl enable pgpool.service #开启自动启动
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添加Pgpool-II运行用户
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useradd postgres # 环境准备时已操作
chown -R postgres.postgres /etc/pgpool-II
chown -R postgres.postgres /var/run/pgpool/
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配置pool_hba.conf
cp /etc/pgpool-II/pool_hba.conf{,.bak}
vi /etc/pgpool-II/pool_hba.conf
增加内容
host all all 0.0.0.0/0 md5
配置pcp.conf
主节点登陆后执行：
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postgres=# select rolname,rolpassword from pg_authid;
rolname | rolpassword
--------------------+-------------------------------------
pg_signal_backend |
srcheck | md5662c10f61b27a9ab38ce69157186b25f
postgres | md5d3612d57ee8d4c147cf27b11e3a0974d
stream_replication | md59279ef6b904bc483e4f85e6d44cfc0ed
(4 rows)
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vi /etc/pgpool-II/pool_passwd
增加SQL执行结果的内容，形式为$rolname:$rolpassword例如：
srcheck:md5662c10f61b27a9ab38ce69157186b25f
或者：
pg_md5 -u postgres your_password
vi /etc/pgpool-II/pcp.conf ## 加入 postgres:上一命令的输出
配置pgpool.conf
cp /etc/pgpool-II/pgpool.conf{,.bak}
vi /etc/pgpool-II/pgpool.conf
内容如下:
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# CONNECTIONS
listen_addresses = '*'
port = 54321
socket_dir = '/var/run/pgpool'
pcp_listen_addresses = '*'
pcp_port = 9898
pcp_socket_dir = '/var/run/pgpool'
# - Backend Connection Settings -
backend_hostname0 = 'master'
backend_port0 = 54321
backend_weight0 = 1
backend_data_directory0 = '/data1/pg_data'
backend_flag0 = 'ALLOW_TO_FAILOVER'
backend_hostname1 = 'slave'
backend_port1 = 54321
backend_weight1 = 1
backend_data_directory1 = '/data1/pg_data'
backend_flag1 = 'ALLOW_TO_FAILOVER'
# - Authentication -
enable_pool_hba = on
pool_passwd = 'pool_passwd'
# FILE LOCATIONS
pid_file_name = '/var/run/pgpool/pgpool.pid'
logdir = '/data1/pg_logs'
replication_mode = off
load_balance_mode = on
master_slave_mode = on
master_slave_sub_mode = 'stream'
sr_check_period = 5
sr_check_user = 'srcheck'
sr_check_password = '123456'
sr_check_database = 'postgres'
# HEALTH CHECK 健康检查
health_check_period = 10
health_check_timeout = 20
health_check_user = 'srcheck'
health_check_password = '123456'
health_check_database = 'postgres'
# FAILOVER AND FAILBACK
failover_command = '/data1/pg_bin/failover_stream.sh %H'
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failover_stream.sh脚本
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vim /data1/pg_bin/failover_stream.sh
chmod 777 /data1/pg_bin/failover_stream.sh
chmod u+s /sbin/ifconfig
chmod u+s /usr/sbin
pgpool -n -d -D > /data1/pg_logs/pgpool.log 2>&1 & ## 启动
pgpool -m fast stop ## 关闭
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failover_stream.sh内容：
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#! /bin/sh
# Failover command for streaming replication.
# Arguments: $1: new master hostname.
new_master=$1
trigger_command="$PGHOME/bin/pg_ctl promote -D $PGDATA"
# Prompte standby database.
/usr/bin/ssh -T $new_master $trigger_command
exit 0;
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登陆设置
当执行pgpool -n -d -D > /data1/pg_logs/pgpool.log 2>&1 &后可查看集群状态：
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[postgres@pool pgpool-II]$ psql -p 54321 -h 10.0.0.13 -U srcheck -d postgres
postgres=# show pool_nodes;
node_id | hostname | port | status | lb_weight | role | select_cnt | load_balance_node | replication_delay
---------+----------+-------+--------+-----------+---------+------------+-------------------+-------------------
0 | master | 54321 | up | 0.500000 | primary | 0 | false | 0
1 | slave | 54321 | up | 0.500000 | standby | 0 | true | 0
(2 rows)
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如果未发现集群状态，请在master和slave主机分别执行以下操作：
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[postgres@pool ~]$ pcp_attach_node -d -U postgres -h pool -p 9898 -n 0
[postgres@pool ~]$ pcp_attach_node -d -U postgres -h pool -p 9898 -n 1
#详情查询命令pcp_attach_node
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HA切换
模拟master主机宕机
Master端：
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[postgres@master ~]$ pg_ctl stop
waiting for server to shut down.... done
server stopped
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当前集群状态
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[postgres@pool ~]$ psql -p 54321 -h 10.0.0.13 -U srcheck -d postgres
psql (9.6.1)
Type "help" for help.
postgres=# show pool_nodes;
node_id | hostname | port | status | lb_weight | role | select_cnt | load_balance_node | replication_delay
---------+----------+------+--------+-----------+---------+------------+-------------------+-------------------
0 | master | 5432 | down| 0.500000 | standby | 0 | false | 0
1 | slave | 5432 | up | 0.500000 | primary | 0 | true | 0
(2 rows)
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发现master已经是standby了，且down机了
修改master，启动
当master主机宕机后，此时slave主机PG数据库成为主库，修改master成为slave的从库即可
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[postgres@master ~]$ vim recovery.conf
standby_mode='on'
primary_conninfo = 'host=slave port=54321 user=stream_replication password=your_password'
restore_command = ''
recovery_target_timeline = 'latest'
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同步时间线
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#如果报时间线冲突落后，先停掉pg服务，然后执行同步时间线，否知直接看状态
[postgres@master ~]$ pg_rewind --target-pgdata=/data1/pg_data --source-server='host=slave port=54321 user=postgres dbname=postgres'
servers diverged at WAL position 0/5000098 on timeline 1
rewinding from last common checkpoint at 0/5000028 on timeline 1
Done!
# 重新启动数据库
[postgres@master ~]$ pg_ctl start
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再次查看当前状态
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[postgres@pool ~]$ psql -p 54321 -h 10.0.0.13 -U srcheck -d postgres
postgres=# show pool_nodes;
node_id | hostname | port | status | lb_weight | role | select_cnt | load_balance_node | replication_delay
---------+----------+------+--------+-----------+---------+------------+-------------------+-------------------
0 | master | 5432 | down| 0.500000 | standby | 0 | false | 0
1 | slave | 5432 | up | 0.500000 | primary | 0 | true | 0
(2 rows)
#注意虽然master已经启动了，但是还是down，需要手动将master节点添加进pgpool，master的node_id是0，所以-n 0
[postgres@pool ~]$ pcp_attach_node -d -U postgres -h pool -p 54321 -n 0
#提示输入密码，输入pcp管理密码
#查看当前状态
[postgres@pool ~]$ psql -p 54321 -h 10.0.0.13 -U srcheck -d postgres
postgres=# show pool_nodes;
node_id | hostname | port | status | lb_weight | role | select_cnt | load_balance_node | replication_delay
---------+----------+------+--------+-----------+---------+------------+-------------------+-------------------
0 | master | 5432 | up | 0.500000 | standby | 0 | false | 0
1 | slave | 5432 | up | 0.500000 | primary | 0 | true | 0
(2 rows)
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现在两个节点都是up了。
主从两节点pgpool健康检查脚本(pgpool_check.sh)
说明：此脚本是基于PGpool只安装到master和slave两个主机上的情况下使用，在master主机有了pgpool进程后，可在slave主机执行sh pgpool_check.sh & 即可
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#! /bin/bash
# Check Master host pgpool-process
while true
do
pgcount=$(nmap 10.0.0.11|egrep '9898|9999'|wc -l)
if [ $pgcount -eq 2 ] ; then
echo 'Master host pgpool is GOOD！！！' > /dev/null 2>&1
else
echo -e "Master host pgpool is \033[31m BAD!!! \033[0m"
echo -e "Master host pgpool is \033[31m BAD!!! \033[0m"
echo -e "Master host pgpool is \033[31m BAD!!! \033[0m"
echo -e "SYSTEM WILL DO THE SHELL : \033[34m su - postgres -c 'pgpool -n -d -D > /data1/pg_logs/pgpool.log 2>&1 &' \033[0m"
su - postgres -c 'pgpool -n -d -D > /data1/pg_logs/pgpool.log 2>&1 &'
pgport=$(netstat -lntup|egrep '9898|9999'|wc -l)
[ $pgport -gt 0 ] && echo -e "Slave host pgpool is \033[32m RUNNING!!! \033[0m"
exit 0
fi
done
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以上为个人经验，希望能给大家一个参考，也希望大家多多支持服务器之家。如有错误或未考虑完全的地方，望不吝赐教。
原文链接：https://blog.csdn.net/weixin_42509278/article/details/81484655