pg_auto_failover 高可用PostgreSQL

1、从软件包安装pg_auto_failover

# Add the repository to your system
curl https://install.citusdata.com/community/rpm.sh | sudo bash
# Install pg_auto_failover
sudo yum install -y pg-auto-failover10_11
# Confirm installation
/usr/pgsql-11/bin/pg_autoctl --version

2、安装并运行监视器

$ export PGDATA=./monitor
$ export PGPORT=5000
$ pg_autoctl create monitor --ssl-self-signed --hostname localhost --auth trust --run

为安装节点 获取监视器节点的后缀 URI（连接字符串）：
$ pg_autoctl show uri --monitor --pgdata ./monitor
postgres://autoctl_node@localhost:5000/pg_auto_failover?sslmode=require

3、安装并运行master PostgreSQL 实例

$ export PGDATA=./node_1
$ export PGPORT=5002
$ pg_autoctl create postgres \
    --hostname localhost \
    --auth trust \
    --ssl-self-signed \
    --monitor 'postgres://autoctl_node@localhost:5000/pg_auto_failover?sslmode=require' \
    --run

4、安装并运行slave PostgreSQL 实例

$ export PGDATA=./node_2
$ export PGPORT=5001
$ pg_autoctl create postgres \
    --hostname localhost \
    --auth trust \
    --ssl-self-signed \
    --monitor 'postgres://autoctl_node@localhost:5000/pg_auto_failover?sslmode=require' \
    --run

5、常用操作

查看系统的状态：
$ pg_autoctl show state
  Name |  Node |      Host:Port |       LSN | Reachable |       Current State |      Assigned State
-------+-------+----------------+-----------+-----------+---------------------+--------------------
node_1 |     1 | localhost:5001 | 0/30000D8 |       yes |             primary |             primary
node_2 |     2 | localhost:5002 | 0/30000D8 |       yes |           secondary |           secondary

启动手动故障转移，也称为切换：
$ pg_autoctl perform switchover

其他命令：
pg_autoctl stop
pg_autoctl drop node --destroy
pg_autoctl drop monitor --destroy

6、查看在应用程序级别使用的连接字符串，请使用以下命令：

$ pg_autoctl show uri --formation default --pgdata ...
postgres://localhost:5002,localhost:5001/postgres?target_session_attrs=read-write&sslmode=require