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PostgreSQL 9.4 : Log shipping Standby Server setup (Step-by-step)


Consider following servers:
  • Master (Production site, 10.88.66.225): Actual production Master site.
  • Storage Server (10.88.66.27): Master would put WAL archived logs on Storage server from where the Slave would pick it up & restore.
  • Slave (Hot Standby Server, 10.88.66.28): Slave would keep on restoring archived WAL files. This would be exact replica of production site. It would be use for read only queries & if production server crashes then Slave would take over the operations.   
Steps for Replication setup:
    • Install the PostgreSQL binary on both Master and Slave servers. Make sure disk mount points for data directory and tablespace directories are same on both the servers.
    • For postgres user setup password less ssh connection between Master, storage and Slave; so that they could copy files across the network.
    • Storage setup:
      • Mount disks & Create storage Directory 
      • Grand read-write permission to postgres user.
      • Export this storage directory and open access to Master and Slave using NFS.
      • Mount the shared directory on Master and slave.
    • Master Configurations:
      • Update the iptables setting to allow TCP connection on port 5432 (postmaster service port)
      • Update /etc/sysconfig/selinux to disable selinux settings.
      • Update postgresql.conf with following parameters
        listen_addresses='*'
        wal_level = hot_standby                                  
        archive_mode = on
        archive_command = 'test -s %p && gzip < %p > /mnt/nfs/archive/%f'
        archive_timeout = 60
        max_wal_senders=3
        wal_keep_segments=32

      • Update pg_hba.conf and add following lines
        host all postgres RemoteIP trust
        host replication postgres SlaveIP trust

      • Restart the postmaster service, now database would be in archive mode and would start copying files on archived location. 
    • Slave Configurations:
      • Mount shared storage directory on slave.
      • Stop postgres database.
      • Move/delete default data directory content, which was created during installation. Make sure data directory is empty, owned by postgres user and directory has permission mode as 700.
      • Backup and restore the base backup from master node:
        pg_basebackup -h 10.88.66.225 -U postgres -D /opt/PostgreSQL/9.4/data -R
      • Update Postgresql.conf with following values:
        listen_addresses='*'
        host_standby='on'
      • Update pg_hba.conf and add following lines
        host all postgres RemoteIP trust
        host replication postgres targetIP trust
      • Update recovery.conf with following values:
        standby_mode='on'
        recovery_target_timeline='latest'
        restore_command = 'test –s /mnt/nfs/archive/%f && gunzip < /mnt/nfs/archive/%f > %p'
        archive_cleanup_command = 'pg_archivecleanup /mnt/nfs/archive %r'
      • Start postgres Database. It would start restoring files from Archived storage location.

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