PostgreSQL在Ubuntu上如何实现高可用

在Ubuntu上实现PostgreSQL的高可用性，可以采用多种方法。以下是一些常见的解决方案：

1. 使用Patroni

Patroni是一个用于管理PostgreSQL高可用性的工具，它基于Raft共识算法。

安装Patroni

sudo apt-get update
sudo apt-get install python3-pip
pip3 install patroni[etcd]

配置Patroni

创建一个Patroni配置文件/etc/patroni.yml，示例配置如下：

scope: postgres
name: postgres_master
namespace: /db/
restapi:
  listen: 0.0.0.0:8008
  connect_address: 127.0.0.1:8008
etcd:
  host: 127.0.0.1:2379
  ttl: 30
  loop_wait: 10
  retry_timeout: 10
  maximum_lag_on_failover: 1048576
  postgresql:
    use_pg_rewind: true
    use_slots: true
    parameters:
      wal_level: replica
      max_connections: 100
      hot_standby: on
      synchronous_commit: off
      archive_mode: on
      archive_command: 'test ! -f /var/lib/postgresql/9.6/main/archive/%f && cp %p /var/lib/postgresql/9.6/main/archive/%f'
      wal_keep_segments: 64
      max_wal_senders: 4
      wal_sender_timeout: 60
      hot_standby_feedback: on
      synchronous_standby_names: '*'
      primary_conninfo:
        dbname: postgres
        user: replicator
        password: replicator
        host: postgres_master
      standby_conninfo:
        dbname: postgres
        user: replicator
        password: replicator
        host: postgres_slave

启动Patroni

sudo patroni /etc/patroni.yml

2. 使用Pgpool-II

Pgpool-II是一个中间件，可以提供负载均衡、故障转移和高可用性。

安装Pgpool-II

sudo apt-get update
sudo apt-get install pgpool2

配置Pgpool-II

编辑/etc/pgpool2/pgpool.conf，示例配置如下：

backend_hostname0 = 'postgres_master'
backend_port0 = 5432
backend_weight0 = 1
backend_data_directory0 = '/var/lib/postgresql/9.6/main'

backend_hostname1 = 'postgres_slave'
backend_port1 = 5432
backend_weight1 = 1
backend_data_directory1 = '/var/lib/postgresql/9.6/main'

load_balance_mode = on
failover_command = '/usr/lib/pgpool2/pgpool_failover.sh %d %h %p %D %m %M %H'
recovery_wait = 0
health_check_period = 10
health_check_timeout = 10

启动Pgpool-II

sudo systemctl start pgpool2
sudo systemctl enable pgpool2

3. 使用Keepalived

Keepalived可以提供虚拟IP地址和故障转移功能。

安装Keepalived

sudo apt-get update
sudo apt-get install keepalived

配置Keepalived

编辑/etc/keepalived/keepalived.conf，示例配置如下：

vrrp_instance VI_1 {
    state MASTER
    interface eth0
    virtual_router_id 51
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1234
    }
    virtual_ipaddress {
        192.168.1.100
    }
}

virtual_server 192.168.1.100 5432 {
    delay_loop 6
    lb_algo rr
    lb_kind DR
    nat_mask 255.255.255.0
    persistence_timeout 50
    protocol TCP

    real_server 192.168.1.101 5432 {
        weight 1
        TCP_CHECK {
            connect_timeout 10
            connect_port 5432
        }
    }

    real_server 192.168.1.102 5432 {
        weight 1
        TCP_CHECK {
            connect_timeout 10
            connect_port 5432
        }
    }
}

启动Keepalived

sudo systemctl start keepalived
sudo systemctl enable keepalived

总结

以上三种方法都可以实现PostgreSQL的高可用性，选择哪种方法取决于你的具体需求和环境。Patroni提供了更全面的解决方案，包括自动故障转移和数据同步；Pgpool-II提供了负载均衡和故障转移功能；Keepalived则提供了虚拟IP地址和故障转移功能。