[pgpool-general: 8770] Re: Difference between pgpool 'primary' and Watchdog 'MASTER' versus the 'load_balance_node'
Bo Peng
pengbo at sraoss.co.jp
Tue May 16 13:56:09 JST 2023
Hi,
> 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
1. primary:
It is the role of *PostgreSQL* nodes.
The role of PostgreSQL nodes can be primary or standby
in streaming replication mode.
2. MASTER:
I think you are asking the status name shown
in the result of pcp_watchdog_info command.
The status name MASTER/STANDBY is the role of *Pgpool-II* node.
If you have multiple Pgpool-II nodes using watchdog feature,
one of them will be elected as MASTER and others will be STANDBY.
3. load_balance_node
Pgpool-II supports for load balancing of SELECT queries.
When a session starts, pgpool will randomly elect one PostgreSQL node
as the load balance node (load_balance_node) and routes SELECTs to
the load_balance_node.
On Mon, 15 May 2023 15:54:53 +0530
Gopikrishnan <nksgopikrishnan at gmail.com> wrote:
> 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*
--
Bo Peng <pengbo at sraoss.co.jp>
SRA OSS LLC
https://www.sraoss.co.jp/
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