[pgpool-general: 6780] Re: Delay in synchronous replication, is it possible ?!

[Franklin Anderson de Oliveira Souza]

Thanks! Bo Peng !

Em qui., 14 de nov. de 2019 às 00:53, Bo Peng <pengbo at sraoss.co.jp>
escreveu:

> Hi,
>
> On Wed, 13 Nov 2019 13:01:07 -0300
> Franklin Anderson de Oliveira Souza <franklinbr at gmail.com> wrote:
>
> > I use pgpool with 5 slave on mode synchronous.
> > But sometimes i see values on column replication_delay when execute
> command
> > show pool_nodes.
> > Sometimes, when a node goes beyond the value of delay_threshold, the node
> > does not receive balancing query.
> >
> > But
> > 1- Synchronous replication should not be delayed is not it?
> > 2- How is this possible ?
> > 3- Is the replication_delay parameter of pgpool wrong?
> >
> > show pool_nodes
> >  node_id |  hostname   | port | status | lb_weight |  role   |
> select_cnt |
> > load_balance_node | replication_delay | last_status_change
> >
> ---------+-------------+------+--------+-----------+---------+------------+-------------------+-------------------+---------------------
> >  0       | IP          | 5432 | up     | 0.100000  | primary |
> 230616548  |
> > false             | 0                 | 2019-10-24 19:17:27
> >  1       | IP          | 5432 | up     | 0.100000  | standby |
> 172466610  |
> > true              | 0                 | 2019-10-24 19:17:27
> >  2       | IP          | 5432 | up     | 0.100000  | standby |
> 180179200  |
> > false             | 234324            | 2019-10-24 19:17:27
> >  3       | IP          | 5432 | up     | 0.100000  | standby |
> 178475037  |
> > false             | 20777216          | 2019-10-24 19:17:27
> >  4       | IP          | 5432 | up     | 0.100000  | standby |
> 182174042  |
> > false             | 0                 | 2019-10-24 19:17:27
> >  5       | IP          | 5432 | up     | 0.100000  | standby |
> 181169375  |
> > false             | 0                 | 2019-10-24 19:17:27
> >
> >
> >
> > pg_stat_replication
> >   application_name  | client_addr |  write_lsn   |  flush_lsn   |
> > write_lag    | sync_priority | sync_state
> >
> --------------------+-------------+--------------+--------------+-----------------+---------------+------------
> >  pje1_slave1        | IP          | 8FA/42E88B60 | 8FA/42E88B60 |
> > 00:00:00.000355 |             1 | sync
> >  pje1_slave2        | IP          | 8FA/42E88B60 | 8FA/42E88B60 |
> > 00:00:00.000312 |             2 | potential
> >  pje1_slave3        | IP          | 8FA/42E88B60 | 8FA/42E88B60 |
> > 00:00:00.000366 |             3 | potential
> >  pje1_slave4        | IP          | 8FA/42E88B60 | 8FA/42E88B60 |
> > 00:00:00.000277 |             4 | potential
> >  pje1_slave5        | IP          | 8FA/42E88B60 | 8FA/42E88B60 |
> > 00:00:00.000265 |             5 | potential
>
> It's the feature of PostgreSQL synchronous replication, not pgpool's issue.
>
> As you can see from pg_stat_replication.sync_state,
> only "pje1_slave1" is a synchronous standby.
> pje1_slave2-5 are "potential" which means asynchronous standby.
>
> See more details:
>
> https://www.postgresql.org/docs/12/monitoring-stats.html#PG-STAT-REPLICATION-VIEW
>
>
> > --
> > foobar
>
>
> --
> Bo Peng <pengbo at sraoss.co.jp>
> SRA OSS, Inc. Japan
>


-- 
foobar
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