一、前提
分别在两台主机上安装好pg数据库，安装过程参考之前文章Centos安装PostgreSQL
二、节点信息
三、部署流复制
#设置hosts（master&&slave）
[root@localhost ~]# cat >> /etc/hosts << EOF
10.1.83.136 master
10.1.83.135 slave
EOF
#初始化master数据库
[root@localhost ~]# su - postgres
[postgres@localhost ~]$ pg_ctl stop -D $PGDATA
[postgres@localhost ~]$ rm -rf /app/postgres/data/
[postgres@localhost ~]$ initdb -D $PGDATA
[postgres@localhost ~]$ pg_ctl start -D $PGDATA
[postgres@localhost ~]$ psql
psql (9.6.0)
Type "help" for help.
postgres=# ALTER ROLE postgres password 'postgres';
ALTER ROLE
postgres=# \q
[postgres@localhost ~]$ vim $PGDATA/postgresql.conf
# - Connection Settings -
listen_addresses = '*'
port = 5432
log_destination = 'stderr'
logging_collector = on
log_directory = '/app/postgres/log/'
log_filename = 'postgresql-%Y-%m-%d_%H%M%S.log'
log_file_mode = 0600
log_rotation_age = 1d
log_rotation_size = 100MB
log_min_messages = error
max_wal_senders = 2
wal_level = replica
archive_mode = on
archive_command = 'cd ./'
hot_standby = on
wal_keep_segments = 64
full_page_writes = on
wal_log_hints = on
[postgres@localhost ~]$ vim $PGDATA/pg_hba.conf
# "local" is for Unix domain socket connections only
local all all md5
# IPv4 local connections:
host all all 127.0.0.1/32 md5
# IPv6 local connections:
host all all ::1/128 md5
# Allow replication connections from localhost, by a user with the
# replication privilege.
#local replication postgres trust
#host replication postgres 127.0.0.1/32 trust
#host replication postgres ::1/128 trust
host all all 0.0.0.0/0 md5
host replication repuser slave md5
[postgres@localhost ~]$ pg_ctl restart -D $PGDATA
[postgres@localhost ~]$ psql
Password:
psql (9.6.0)
Type "help" for help.
postgres=# CREATE USER repuser replication LOGIN CONNECTION LIMIT 3 ENCRYPTED PASSWORD 'repuser';
CREATE ROLE
postgres=# \q
#部署slave数据库
[root@localhost ~]# su - postgres
[postgres@localhost ~]$ rm -rf /app/postgres/data/
[postgres@localhost ~]$ pg_basebackup -D $PGDATA -Fp -Xs -v -P -h master -p 5432 -U repuser
[postgres@localhost ~]$ vim $PGDATA/pg_hba.conf
host replication repuser PG_master md5
#配置master的recovery.done
[postgres@localhost ~]$ cd $PGHOME
[postgres@localhost postgres]$ cp share/recovery.conf.sample data/recovery.done
[postgres@localhost postgres]$ vim data/recovery.done
recovery_target_timeline='latest'
standby_mode=on
primary_conninfo='host=slave port=5432 user=repuser password=repuser'
trigger_file='/app/postgres/data/trigger_file'
#配置slave的recovery.conf
[postgres@localhost ~]$ cd $PGHOME
[postgres@localhost postgres]$ cp share/recovery.conf.sample data/recovery.conf
[postgres@localhost postgres]$ vim data/recovery.conf
recovery_target_timeline='latest'
standby_mode=on
primary_conninfo='host=master port=5432 user=repuser password=repuser'
trigger_file='/app/postgres/data/trigger_file'
#配置master的.pgpass
[postgres@localhost postgres]$ echo 'master:5432:postgres:repuser:repuser' > /home/postgres/.pgpass;chmod 0600 /home/postgres/.pgpass
#配置slave的.pgpass
[postgres@localhost postgres]$ echo 'master:5432:postgres:repuser:repuser' > /home/postgres/.pgpass;chmod 0600 /home/postgres/.pgpass
四、流复制数据同步测试
分别重启master，slave数据库
#在master插入数据
[postgres@localhost ~]$ psql
Password:
psql (9.6.0)
Type "help" for help.
postgres=# create database test;
CREATE DATABASE
postgres=# \c test
You are now connected to database "test" as user "postgres".
test=# create table tt(id serial not null,name text);
CREATE TABLE
test=# insert into tt(name) values ('china');
INSERT 0 1
test=# \q
#在slave查看master插入的数据是否同步过来
[postgres@localhost ~]$ psql
Password:
psql (9.6.0)
Type "help" for help.
postgres=# \c test
You are now connected to database "test" as user "postgres".
test=# select * from tt;
id | name
----+-------
1 | china
(1 row)
test=# \q
五、流复制管理
一般可以通过若干命令查询数据库的主备属性，主数据库是读写的，备数据库是只读的。当主数据库宕机了，可以通过建立触发文件，备数据库将被提升为主数据库，实现一些基本的HA应用。
#查看主备属性
[postgres@localhost ~]$ pg_controldata | grep 'Database cluster state'
主机的cluster state是in production，备机的cluster state是in archive recovery。
#字典表pg_stat_replication
[postgres@localhost ~]$ psql
Password:
psql (9.6.0)
Type "help" for help.
postgres=# select pid,application_name,client_addr,client_port,state,sync_state from pg_stat_replication;
pid | application_name | client_addr | client_port | state | sync_state
------+------------------+-------------+-------------+-----------+------------
1401 | walreceiver | 10.1.83.135 | 48860 | streaming | async
在主机字典表中是能查到记录，备机中是查询不到的。
#进程信息识别
[postgres@localhost ~]$ ps -ef | grep postgres | grep 'wal sender\|wal receiver' | grep -v grep
进程中显示wal sender的是主机，显示wal receiver的是备机
#pg函数
[postgres@localhost ~]$ psql
Password:
psql (9.6.0)
Type "help" for help.
postgres=# select pg_is_in_recovery();
备机是t，主机是f。
#切换主从
1、master关闭
[postgres@localhost ~]$ pg_ctl stop -D $PGDATA
2、slave触发切换流程
[postgres@localhost ~]$ touch /app/postgres/data/trigger_file
[postgres@localhost ~]$ pg_controldata | grep 'Database cluster state'
Database cluster state: in production
[postgres@localhost ~]$ psql
Password:
psql (9.6.0)
Type "help" for help.
postgres=# \c test
You are now connected to database "test" as user "postgres".
test=# insert into tt(name) values('sdf');
INSERT 0 1
3、master恢复后，重新作为new slave
[postgres@localhost data]$ mv recovery.done recovery.conf
#启动pg服务
[postgres@master data]$ pg_ctl start -D $PGDATA
#查看日志，看切换后，是否需要拉取增量数据，如果需要则执行以下步骤，如果不需要则跳过以下步骤
[postgres@master data]$ less /app/postgres/log/postgresql-2020-01-08_154428.log
如果出现如下ERROR日志，则需要拉取增量数据
ERROR: requested starting point 0/6000000 on timeline 1 is not in this server's history
DETAIL: This server's history forked from timeline 1 at 0/4000098.
ERROR: requested starting point 0/6000000 on timeline 1 is not in this server's history
DETAIL: This server's history forked from timeline 1 at 0/4000098.
ERROR: requested starting point 0/6000000 on timeline 1 is not in this server's history
[postgres@master data]$ pg_ctl stop -D $PGDATA
[postgres@master ~]$ pg_rewind --target-pgdata=/app/postgres/data --source-server='host=slave port=5432 user=postgres dbname=postgres password=postgres'
[postgres@master ~]$ pg_ctl start -D $PGDATA
#查看增量数据，是否已拉取过来
[postgres@master ~]$ psql
Password:
psql (9.6.0)
Type "help" for help.
postgres=# \c test
You are now connected to database "test" as user "postgres".
test=# select * from tt;
id | name
----+-------
1 | china
34 | sdf
(2 rows)