[pgpool-general: 8781] Re: Difference between pgpool 'primary' and Watchdog 'MASTER' versus the 'load_balance_node'
Gopikrishnan
nksgopikrishnan at gmail.com
Mon May 29 19:02:26 JST 2023
Thank you for the clarifications.
So my understanding currently is :
-----------
1. database '*primary*' node failure is the event controlling the failover
process. (executing failover.sh)
2. Watchdog `*MASTER*` failure only causes the VIP to move to another node.
That is unless of course watchdog master is also the
current pgpool primary node, in which case a failover will be triggered.
3. *esc.sh* and *desc.sh *only concerns the watchdog MASTER/STANDBY
Am I correct?
*Thanks*
*Gopi*
On Mon, May 29, 2023 at 2:10 PM Tatsuo Ishii <ishii at sraoss.co.jp> wrote:
> >> Hi pgpool experts,
> >>
> >> Can you please clarify the below?
> >> *During failover, Is the '*primary*' or '*MASTER*' or '
> *load_balance_node*
> >> failure taken into account?*
> >
> > It's hard to answer your question as the question is too vague. Anyway I
> try it...
> >
> > - primary failure is taken into account because it triggers failover.
> > See
> https://www.pgpool.net/docs/44/en/html/runtime-config-failover.html for
> more details.
> >
> > - MASTER and other watchdog nodes are taken into account in failover.
> > See
> >
> https://www.pgpool.net/docs/44/en/html/runtime-watchdog-config.html#CONFIG-WATCHDOG-FAILOVER-BEHAVIOR
> > for more details.
> >
> > - Load balance node is not taken into account in streaming replication
> mode.
> > See note #2 in
> https://www.pgpool.net/docs/44/en/html/runtime-config-failover.html for
> more details.
>
> Sorry, I meant "Load balance node is taken into account".
>
> >>
> >> *Thanks*
> >> *Gopi*
> >>
> >>
> >> On Tue, May 16, 2023 at 10:56 AM Gopikrishnan <
> nksgopikrishnan at gmail.com>
> >> wrote:
> >>
> >>> 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/
> >>>>
> >>>
> > _______________________________________________
> > pgpool-general mailing list
> > pgpool-general at pgpool.net
> > http://www.pgpool.net/mailman/listinfo/pgpool-general
>
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