[pgpool-general: 8767] Difference between pgpool 'primary' and Watchdog 'MASTER' versus the 'load_balance_node'

[Gopikrishnan]

Hi folks,

Need your help in clearing a confusion regd. basic terminologies:

Regd. which I couldn't gather much from the docs at:
https://www.pgpool.net/docs/pgpool-II-4.0.4/


   1. primary
   2. MASTER
   3. load_balance_node

I have a pgpool with 3 nodes. I have a confusion between the pgpool primary and
the watchdog *MASTER* and the `*load_balance_node*`

In my setup, the pgpool primary node (according to show pool_nodes output)
is : *10.108.104.31, *and also the node designated *load_balance_node*.

While the MASTER node, according to pgpool watchdog, is: *10.108.104.32* And
the *cluster virtual IP* is attached to this node.

I have the following questions in mind:


   1. What do the terms '*primary*' and '*MASTER*' and *load_balance_node*
   mean?
   2. During failover, Is the '*primary*' or '*MASTER*' or '
   *load_balance_node* failure taken into account?
   3. What is the difference (or any relation) between the '*primary*' and '
   *MASTER*' and *load_balance_node* nodes?
   4. If the cluster virtual IP is on the non '*primary*' node, wouldn't it
   affect the performance of the HA setup?

Below are the outputs for *show pool_nodes *and* watchdog *info:

psql -h delegateIP -p 9999 -U pgpool postgres -c "show pool_nodes"
Password for user pgpool:
 node_id |   hostname    | port | status | lb_weight |  role   |
select_cnt | load_balance_node | replication_delay |
last_status_change---------+---------------+------+--------+-----------+---------+------------+-------------------+-------------------+---------------------
 0       | 10.108.104.31 | 5432 | up     | 0.333333  | primary | 0
     | true              | 0                 | 2023-05-12 12:07:13
 1       | 10.108.104.32 | 5432 | up     | 0.333333  | standby | 0
     | false             | 0                 | 2023-05-12 12:07:13
 2       | 10.108.104.33 | 5432 | down   | 0.333333  | standby | 0
     | false             | 0                 | 2023-05-12 12:07:13
(3 rows)

And the Watchdog info:

pcp_watchdog_info -h localhost -vw -U pgpool
Watchdog Cluster Information
Total Nodes          : 3
Remote Nodes         : 2
Quorum state         : QUORUM EXIST
Alive Remote Nodes   : 2
VIP up on local node : NO
Master Node Name     : vm-104-32.eng.dev.com:9999 Linux vm-104-32.eng.dev.com
Master Host Name     : 10.108.104.32

Watchdog Node Information
Node Name      : vm-104-31.eng.dev.com:9999 Linux vm-104-31.eng.dev.com
Host Name      : vm-104-31.eng.dev.com
Delegate IP    : 10.108.104.34
Pgpool port    : 9999
Watchdog port  : 9000
Node priority  : 1
Status         : 7
Status Name    : STANDBY

Node Name      : vm-104-32.eng.dev.com:9999 Linux vm-104-32.eng.dev.com
Host Name      : 10.108.104.32
Delegate IP    : 10.108.104.34
Pgpool port    : 9999
Watchdog port  : 9000
Node priority  : 1
Status         : 4
Status Name    : MASTER

Node Name      : vm-104-33.eng.dev.com:9999 Linux vm-104-33.eng.dev.com
Host Name      : 10.108.104.33
Delegate IP    : 10.108.104.34
Pgpool port    : 9999
Watchdog port  : 9000
Node priority  : 1
Status         : 7
Status Name    : STANDBY



*Thanks & Regards*
*Gopi*
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