7.2. Watchdog Configuration Example

7.2.1.1. Enabling watchdog

First of all, set use_watchdog to on.

use_watchdog = on
# Activates watchdog
              

7.2.1.2. Configure Up stream servers

Specify the up stream servers (e.g. application servers). Leaving it blank is also fine.

trusted_servers = ''
  # trusted server list which are used
  # to confirm network connection
  # (hostA,hostB,hostC,...)
	    

7.2.1.3. Watchdog Communication

Specify the TCP port number for watchdog communication.

wd_port = 9000
  # port number for watchdog service
	    

7.2.1.4. Virtual IP

Specify the IP address to be used as a virtual IP address in the delegate_IP.

delegate_IP = '133.137.177.143'
# delegate IP address
              

7.2.2.1. Active (osspc16) Server configurations

other_pgpool_hostname0 = 'osspc20'
  # Host name or IP address to connect to for other pgpool 0
other_pgpool_port0 = 9999
  # Port number for other pgpool 0
other_wd_port0 = 9000
  # Port number for other watchdog 0
	    

7.2.2.2. Standby (osspc20) Server configurations

other_pgpool_hostname0 = 'osspc16'
  # Host name or IP address to connect to for other pgpool 0
other_pgpool_port0 = 9999
  # Port number for other pgpool 0
other_wd_port0 = 9000
  # Port number for other watchdog 0
	    

7.2.3.1. Starting pgpool in Active server (osspc16)

First start the Pgpool-II on Active server.

[user@osspc16]$ su -
[root@osspc16]# {installed_dir}/bin/pgpool -n -f {installed_dir}/etc/pgpool.conf > pgpool.log 2>&1
	    

Log messages will show that Pgpool-II has the virtual IP address and starts watchdog process.

LOG:  I am announcing my self as master/coordinator watchdog node
LOG:  I am the cluster leader node
DETAIL:  our declare coordinator message is accepted by all nodes
LOG:  I am the cluster leader node. Starting escalation process
LOG:  escalation process started with PID:59449
LOG:  watchdog process is initialized
LOG:  watchdog: escalation started
LOG:  I am the master watchdog node
  DETAIL:  using the local backend node status
	    

7.2.3.2. Starting pgpool in Standby server (osspc20)

Now start the Pgpool-II on Standby server.

[user@osspc20]$ su -
[root@osspc20]# {installed_dir}/bin/pgpool -n -f {installed_dir}/etc/pgpool.conf > pgpool.log 2>&1
	    

Log messages will show that Pgpool-II has joind the watchdog cluster as standby watchdog.

LOG:  watchdog cluster configured with 1 remote nodes
LOG:  watchdog remote node:0 on Linux_osspc16_9000:9000
LOG:  interface monitoring is disabled in watchdog
LOG:  IPC socket path: "/tmp/.s.PGPOOLWD_CMD.9000"
LOG:  watchdog node state changed from [DEAD] to [LOADING]
LOG:  new outbound connection to Linux_osspc16_9000:9000
LOG:  watchdog node state changed from [LOADING] to [INITIALIZING]
LOG:  watchdog node state changed from [INITIALIZING] to [STANDBY]
LOG:  successfully joined the watchdog cluster as standby node
DETAIL:  our join coordinator request is accepted by cluster leader node "Linux_osspc16_9000"
LOG:  watchdog process is initialized
	    

7.2.6.1. Lifecheck

There are the parameters about watchdog's monitoring. Specify the interval to check wd_interval, the count to retry wd_life_point, the qyery to check wd_lifecheck_query and finaly the type of lifecheck wd_lifecheck_method.

wd_lifecheck_method = 'query'
      # Method of watchdog lifecheck ('heartbeat' or 'query' or 'external')
      # (change requires restart)
wd_interval = 10
      # lifecheck interval (sec) > 0
wd_life_point = 3
      # lifecheck retry times
wd_lifecheck_query = 'SELECT 1'
      # lifecheck query to pgpool from watchdog
		    

7.2.6.2. Switching virtual IP address

There are the parameters for switching the virtual IP address. Specify switching commands if_up_cmd, if_down_cmd, the path to them if_cmd_path, the command executed after switching to send ARP request arping_cmd and the path to it arping_path.

ifconfig_path = '/sbin'
# ifconfig command path
if_up_cmd = 'ifconfig eth0:0 inet $_IP_$ netmask 255.255.255.0'
# startup delegate IP command
if_down_cmd = 'ifconfig eth0:0 down'
# shutdown delegate IP command

arping_path = '/usr/sbin'           # arping command path

arping_cmd = 'arping -U $_IP_$ -w 1'
		      

You can also use the custom scripts to bring up and bring down the virtual IP using wd_escalation_command and wd_de_escalation_command configurations.