PostgreSQL流复制实现HA主备切换
环境说明和主机规划
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）
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
创建postgres用户
useradd postgres && echo "your_password" | passwd --stdin postgres
配置免密钥登陆
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
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
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
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:
# Include the default config: .include /usr/lib/systemd/system/postgresql-9.6.service [Service] Environment=PGDATA=/data1/pg_data
重启PG服务
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
修改系统配置（以下用postgres用户操作）
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
64G
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
128G
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'
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:
# Include the default config: .include /usr/lib/systemd/system/postgresql-9.6.service [Service] Environment=PGDATA=/data1/pg_data
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 $PGDATA/recovery.conf
增加以下内容
standby_mode='on' primary_conninfo = 'host=master port=54321 user=stream_replication password=your_password' restore_command = '' recovery_target_timeline = 'latest' # 重启PG服务 systemctl restart postgresql-9.6 systemctl enable postgresql-9.6.service
验证
主节点执行
create table test (id int4, create_time timestamp(0) without time zone); insert into test values (1, now()); select * from test;
备节点执行
select * from test;
其他查询
进入测试数据库test，主库上执行如下命令返回f，备库上返回t。 select pg_is_in_recovery();
执行如下命令查看快照，它返回主库记录点、备库记录点；主库每增加一条写入，记录点的值就会加1。
select txid_current_snapshot();
执行如下命令可以查看主备同步状态。
select * from pg_stat_replication;
字段state显示的同步状态有：startup（连接中）、catchup（同步中）、streaming（同步）；字段sync_state显示的模式有：async（异步）、sync（同步）、potential（虽然现在是异步模式，但是有可能升级到同步模式）。
主备切换
假设主库崩溃了，备库如何从只读状态切换为读写状态呢？只要把备库的postgresql.conf中hot_standby修改为off，并且删除recovery.conf，然后重启库就可以提供服务了。
PGPool2（pool主机操作）
安装PGPool2
yum install -y http://www.pgpool.net/yum/rpms/3.6/redhat/rhel-7-x86_64/pgpool-II-release-3.6-1.noarch.rpm yum -y install pgpool-II-pg96 pgpool-II-pg96-debuginfo pgpool-II-pg96-devel pgpool-II-pg96-extensions systemctl enable pgpool.service #开启自动启动
添加Pgpool-II运行用户
useradd postgres # 环境准备时已操作 chown -R postgres.postgres /etc/pgpool-II chown -R postgres.postgres /var/run/pgpool/
配置pool_hba.conf
cp /etc/pgpool-II/pool_hba.conf{,.bak}
vi /etc/pgpool-II/pool_hba.conf
增加内容
host all all 0.0.0.0/0 md5
配置pcp.conf
主节点登陆后执行：
postgres=# select rolname,rolpassword from pg_authid; rolname | rolpassword --------------------+------------------------------------- pg_signal_backend | srcheck | md5662c10f61b27a9ab38ce69157186b25f postgres | md5d3612d57ee8d4c147cf27b11e3a0974d stream_replication | md59279ef6b904bc483e4f85e6d44cfc0ed (4 rows)
vi /etc/pgpool-II/pool_passwd
增加SQL执行结果的内容，形式为$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:
# 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'
failover_stream.sh脚本
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
failover_stream.sh内容：
#! /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 $trigger_command exit 0;
登陆设置
当执行pgpool -n -d -D > /data1/pg_logs/pgpool.log 2>&1 &后可查看集群状态：
[postgres@pool pgpool-II]$ 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)
如果未发现集群状态，请在master和slave主机分别执行以下操作：
[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
HA切换
模拟master主机宕机
Master端：
[postgres@master ~]$ pg_ctl stop waiting for server to shut down.... done server stopped
当前集群状态
[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)
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
[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'
同步时间线
#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
再次查看当前状态
[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 | 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)
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
#! /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
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。如有错误或未考虑完全的地方，望不吝赐教。
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