[pgpool-general: 8771] Re: Difference between pgpool 'primary' and Watchdog 'MASTER' versus the 'load_balance_node'

[Gopikrishnan]

Thank you for your response!

Can you also kindly clarify this:
 During failover, Is the '*primary*' or '*MASTER*' or ' *load_balance_node*
failure taken into account?

*Thanks*
*Gopi*


On Tue, May 16, 2023 at 10:26 AM Bo Peng <pengbo at sraoss.co.jp> wrote:

> 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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