2-node: dual

Dual-node template to set up a basic high-availability PostgreSQL cluster with master-slave replication, tolerating the failure of one node.

Overview

Conf Name: dual
Node Count: 2-node, pigsty/vagrant/spec/dual.rb
Description: Dual-node template to set up a basic high-availability PostgreSQL cluster with master-slave replication, tolerating the failure of one node.
OS Distro: el8, el9, d12, u22, u24
OS Arch: x86_64, aarch64
Related:

Description

启用方式：在 configure 过程中使用 -c dual 参数：

./configure -c dual [-i <primary_ip>]

配置生成完成后，您还需要将 10.10.10.11 占位节点 IP 地址修改为您的从库节点 IP 地址。

Content

源文件地址：pigsty/conf/dual.yml

all:
  children:

    # infra cluster for proxy, monitor, alert, etc..
    infra: { hosts: { 10.10.10.10: { infra_seq: 1 } } }

    # etcd cluster for ha postgres
    etcd: { hosts: { 10.10.10.10: { etcd_seq: 1 } }, vars: { etcd_cluster: etcd } }

    # minio cluster, optional backup repo for pgbackrest
    #minio: { hosts: { 10.10.10.10: { minio_seq: 1 } }, vars: { minio_cluster: minio } }

    # postgres cluster 'pg-dual' with single primary instance
    pg-dual:
      hosts:
        10.10.10.10: { pg_seq: 1, pg_role: replica }
        10.10.10.11: { pg_seq: 2, pg_role: primary }  # <----- use this as primary by default
      vars:
        pg_cluster: pg-dual
        pg_databases: [ { name: dual ,baseline: cmdb.sql ,comment: pigsty dual database ,schemas: [ pigsty ] ,extensions: [ { name: vector }] } ]
        pg_users:
          - { name: dbuser_dual ,password: DBUser.Meta   ,pgbouncer: true ,roles: [ dbrole_admin ]    ,comment: pigsty admin user }
          - { name: dbuser_view ,password: DBUser.Viewer ,pgbouncer: true ,roles: [ dbrole_readonly ] ,comment: read-only viewer for dual database }
        node_crontab: [ '00 01 * * * postgres /pg/bin/pg-backup full' ] # make a full backup every 1am
        pg_vip_enabled: true
        pg_vip_address: 10.10.10.2/24
        pg_vip_interface: eth1

  vars:                               # global parameters
    version: v3.1.0                   # pigsty version string
    admin_ip: 10.10.10.10             # admin node ip address
    region: default                   # upstream mirror region: default,china,europe
    infra_portal:                     # domain names and upstream servers
      home         : { domain: h.pigsty }
      grafana      : { domain: g.pigsty ,endpoint: "${admin_ip}:3000" , websocket: true }
      prometheus   : { domain: p.pigsty ,endpoint: "${admin_ip}:9090" }
      alertmanager : { domain: a.pigsty ,endpoint: "${admin_ip}:9093" }
      blackbox     : { endpoint: "${admin_ip}:9115" }
      loki         : { endpoint: "${admin_ip}:3100" }
      #minio        : { domain: sss.pigsty  ,endpoint: "${admin_ip}:9001" ,scheme: https ,websocket: true }

    # consider using local fs or external s3 service for cold backup storage in dual node configuration
    #pgbackrest_method: minio

...

Caveat

通常在生产环境中，完整的高可用部署至少需要三个节点，以确保在任何一台服务器宕机时，集群仍然可以正常运行。因为高可用故障检测 DCS（etcd） / Patroni需要多数节点的参与，而双节点无法满足这一要求。

但是，有时候只有两台服务器可用，这种情况下，dual 模板是一个可行的选择，假设您有两台服务器：

节点A，10.10.10.10 ，默认为管理节点，运行 Infra 基础设施，单节点 etcd，以及 PGSQL 的从库。
节点B，10.10.10.11 ，只做为 PGSQL 的主库。

在这种情况下，两节点模版允许 B 节点出现故障，并在故障发生后自动切换到 A 节点。然而当 A 节点出现故障时（整个节点宕机），则需要人工介入。不过，如果 A 节点不是整个节点宕机离线，而仅仅是 etcd 或 PostgreSQL 本身的问题，整套系统仍然可以继续正常运行。

此模板使用了一个 L2 VIP 实现高可用接入，如果您的网络条件不允许使用 L2 VIP （例如，在受限制的云环境，或跨交换机广播域），您可以考虑使用 DNS 解析或其他接入方式替代。

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Last modified 2024-11-13: routine update (58464bf2)