centos postgresql如何进行负载均衡

在CentOS上实现PostgreSQL的负载均衡，可以采用多种方法。以下是一些常见的解决方案：

1. 使用Pgpool-II

Pgpool-II是一个中间件，可以在多个PostgreSQL服务器之间进行负载均衡和故障转移。

安装Pgpool-II

sudo yum install pgpool2

配置Pgpool-II

编辑/etc/pgpool2/pgpool.conf文件，配置后端PostgreSQL服务器：

backend_hostname0 = 'primary_server_ip'
backend_port0 = 5432
backend_weight0 = 1

backend_hostname1 = 'secondary_server_ip'
backend_port1 = 5432
backend_weight1 = 1

启动Pgpool-II

sudo systemctl start pgpool2
sudo systemctl enable pgpool2

2. 使用HAProxy

HAProxy是一个高性能的TCP/HTTP负载均衡器，也可以用于PostgreSQL的负载均衡。

安装HAProxy

sudo yum install haproxy

配置HAProxy

编辑/etc/haproxy/haproxy.cfg文件，添加PostgreSQL后端配置：

frontend postgres_frontend
    bind *:5432
    default_backend postgres_backend

backend postgres_backend
    balance roundrobin
    server primary_server primary_server_ip:5432 check
    server secondary_server secondary_server_ip:5432 check

启动HAProxy

sudo systemctl start haproxy
sudo systemctl enable haproxy

3. 使用Keepalived

Keepalived可以提供高可用性和负载均衡，通常与LVS（Linux Virtual Server）一起使用。

安装Keepalived

sudo yum install keepalived

配置Keepalived

编辑/etc/keepalived/keepalived.conf文件，配置VRRP和虚拟IP：

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

4. 使用Patroni

Patroni是一个用于管理PostgreSQL高可用性的工具，支持自动故障转移和负载均衡。

安装Patroni

sudo yum install patroni

配置Patroni

编辑/etc/patroni.yml文件，配置PostgreSQL集群：

scope: postgresql
name: my_cluster
namespace: /db/
restapi:
  listen: 0.0.0.0:8008
  connect_address: 192.168.1.100
etcd:
  host: 192.168.1.100
  port: 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
      synchronous_standby_names: '*'
      max_wal_senders: 4
      wal_keep_segments: 8
      max_replication_slots: 4
      track_commit_timestamp: on
      synchronous_timeout: 30s
      checkpoint_completion_target: 0.9
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default_statistics_target: 100
      random_page_cost: 1.1
      effective_cache_size: 75% of total RAM
      maintenance_work_mem: 1GB
      shared_buffers: 25% of total RAM
      work_mem: 4MB
      checkpoint_segments: 16
      wal_buffers: 16MB
      default