PostgreSQL HA

Install and configure a PostgreSQL high-availability cluster managed with repmgr. Add dependencies, extensions, databases and users. Works for standalone installations as well.

Tested with :

• Debian 10.x ✔️
• Debian 11.x ✔️
• Ubuntu 18.04.x ✔️
• Ubuntu 20.04.x ✔️

---

• PostgreSQL HA
  • Requirements
  • Installation
  • Dependencies
  • Example Inventory
  • Role variables
  • Example Playbook
• Usefull commands to run after your first installation
  • Verifying cluster functionality
  • Show cluster status
  • List nodes and their attributes
  • Register (clone) an additionnal standby node
• Register former primary as a standby node after automatic failover
• License

Requirements

• Python >=3.8
• Ansible-core >=2.12

See ./requirements.txt for detailled dependencies used to develop the role.

Recommended, for each postgresql host

• Python3 in PATH
• Pip3 in PATH
• psycopg2-binary (itself requires libpq-dev apt-package)

You can take a look at prepare.yml to check out an example setup for Python 3.

Installation

Shell

ansible-galaxy collection install community.crypto
ansible-galaxy install fidanf.postgresql_ha

Requirements file

---
roles:
- src: https://github.com/fidanf/ansible-role-postgresql-ha
  name: fidanf.postgresql_ha
  version: master

collections:
  - community.crypto

Dependencies

• cryptography (ansible host)

Example Inventory

See inventory.yml for detailed group and host vars.

Role variables

Role default variables are split amongst two files :

• 001-postgresql.yml
• 002-repmgr.yml

In order to exactly figure out the purpose and valid values for each of these variables, do not hesitate to inspect all the Jinja templates in the templates directory. Original default configuration files are also included (.orig).

Example Playbook

---
- hosts: pgcluster
  gather_facts: yes
  become: yes
  roles:
    - name: fidanf.postgresql_ha
      vars:
        # Required configuration items
        repmgr_target_group: pgcluster
        repmgr_master: pgsql01
        repmgr_failover: automatic
        repmgr_promote_command: /usr/bin/repmgr standby promote -f /etc/repmgr.conf --log-to-file
        repmgr_follow_command: /usr/bin/repmgr standby follow -f /etc/repmgr.conf --log-to-file --upstream-node-id=%n
        repmgr_monitoring_history: "yes"
        repmgr_connection_check_type: query
        repmgr_log_level: DEBUG
        repmgr_reconnect_attempts: 2
        repmgr_reconnect_interval: 10
        # Basic settings
        postgresql_version: 13
        postgresql_cluster_name: main
        postgresql_cluster_reset: false # TODO: Needs to be tested for repmgr
        postgresql_listen_addresses: "*"
        postgresql_port: 5432
        postgresql_wal_level: "replica"
        postgresql_max_wal_senders: 10
        postgresql_max_replication_slots: 10
        postgresql_wal_keep_segments: 100
        postgresql_hot_standby: on
        postgresql_archive_mode: on
        postgresql_archive_command: "test ! -f /tmp/%f && cp %p /tmp/%f"
        postgresql_ext_install_repmgr: yes
        postgresql_shared_preload_libraries:
          - repmgr
        # postgresql logging 
        postgresql_log_checkpoints: on
        postgresql_log_connections: on
        postgresql_log_disconnections: on
        postgresql_log_temp_files: 0
        # pg_hba.conf
        postgresql_pg_hba_custom:
          - { type: "host", database: "all", user: "all", address: "192.168.56.0/24", method: "md5" }
          - { type: "host", database: "replication", user: "{{ repmgr_user }}", address: "192.168.56.0/24", method: "trust" }  
          - { type: "host", database: "replication", user: "{{ repmgr_user }}", address: "127.0.0.1/32", method: "trust" }  
          - { type: "host", database: "{{ repmgr_database }}", user: "{{ repmgr_user }}", address: "127.0.0.1/32", method: "trust" }  
          - { type: "host", database: "{{ repmgr_database }}", user: "{{ repmgr_user }}", address: "192.168.56.0/32", method: "trust" }  
        # Databases
        postgresql_databases:
          - name: "{{ repmgr_database }}"
            owner: "{{ repmgr_user }}"
            encoding: "UTF-8"
          - name: testdb
            owner: admin
            encoding: "UTF-8"
        # Users
        postgresql_users:
          - name: "{{ repmgr_user }}"
            pass: "{{ repmgr_password }}"
          - name: admin
            pass: secret # postgresql >=10 does not accept unencrypted passwords
            encrypted: yes
        # Roles
        postgresql_user_privileges:
          - name: "{{ repmgr_user }}"
            db: "{{ repmgr_database }}"
            priv: "ALL"
            role_attr_flags: "SUPERUSER,REPLICATION"
          - name: admin
            db: testdb
            role_attr_flags: "SUPERUSER"

Usefull commands to run after your first installation

Verifying cluster functionality

ansible pgcluster -b --become-user postgres -m shell -a "repmgr cluster crosscheck"

Show cluster status

ansible pgcluster -b --become-user postgres -m shell -a "repmgr cluster show"

List nodes and their attributes

ansible pgcluster -b --become-user postgres -m shell -a "repmgr node status"

Register (clone) an additionnal standby node

# Assuming the current primary hostname is pgsql01
ansible-playbook myplaybook.yml -l 'pgsql04' -e 'repmgr_primary_hostname=pgsql01' -vv 

Register former primary as a standby node after automatic failover

postgres@pgsql01:~$ pg_ctlcluster 13 main stop
postgres@pgsql01:~$ repmgr standby clone --force -h pgsql02 -U repmgr -d repmgr
postgres@pgsql01:~$ pg_ctlcluster 13 main start
postgres@pgsql01:~$ repmgr standby register --force

Or you may use the repmgr node rejoin with pg_rewind

repmgr node rejoin -d repmgr -U repmgr -h pgsql02 --verbose --force-rewind=/usr/lib/postgresql/13/bin/pg_rewind

License

MIT / BSD