Reading WALs
On my built in logical replication I see that sometimes it tooks a long time
to be updated with master. The question is how can I see what is being done
on replica ? I know I can have a WAL reader, I tried WAL2JSON, it listen all
data which comes from master, but as I understood when I use that plugin
that data is discarded, so, not replicated.
Is that correct ? Can I see what is coming to replica server and apply that
change to server as usual ?
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Sent from: https://www.postgresql-archive.org/PostgreSQL-general-f1843780.html
On 3/14/20 6:48 AM, PegoraroF10 wrote:
On my built in logical replication I see that sometimes it tooks a long time
to be updated with master. The question is how can I see what is being done
on replica ? I know I can have a WAL reader, I tried WAL2JSON, it listen all
data which comes from master, but as I understood when I use that plugin
that data is discarded, so, not replicated.Is that correct ? Can I see what is coming to replica server and apply that
change to server as usual ?
See what is happening:
https://www.postgresql.org/docs/12/monitoring-stats.html#PG-STAT-SUBSCRIPTION
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--
Adrian Klaver
adrian.klaver@aklaver.com
pg_Stat_Subscription does not anwer what I want. This view just show if
replication is being processed but not exactly what it´s doing.
Is it replicating a huge table which an erroneous proess updated several
times ?
Replication process is recreating what index and that is spending how much
time ?
What WAL, table, operation is the one being processed ?
So I would like to have a listener on replica server just to see all WAL
info is coming, just that.
Then I can go back to production and see what´s could run better, if
application, triggers and so on.
--
Sent from: https://www.postgresql-archive.org/PostgreSQL-general-f1843780.html
On 3/14/20 10:11 AM, PegoraroF10 wrote:
pg_Stat_Subscription does not anwer what I want. This view just show if
replication is being processed but not exactly what it´s doing.
Is it replicating a huge table which an erroneous proess updated several
times ?
Replication process is recreating what index and that is spending how much
time ?
What WAL, table, operation is the one being processed ?So I would like to have a listener on replica server just to see all WAL
info is coming, just that.
Any of the below helpful?:
https://www.postgresql.org/docs/12/logicaldecoding-example.html
Then I can go back to production and see what´s could run better, if
application, triggers and so on.--
Sent from: https://www.postgresql-archive.org/PostgreSQL-general-f1843780.html
--
Adrian Klaver
adrian.klaver@aklaver.com
On 2020-03-14 14:48, PegoraroF10 wrote:
On my built in logical replication I see that sometimes it tooks a long time
to be updated with master. The question is how can I see what is being done
on replica ? I know I can have a WAL reader, I tried WAL2JSON, it listen all
data which comes from master, but as I understood when I use that plugin
that data is discarded, so, not replicated.Is that correct ? Can I see what is coming to replica server and apply that
change to server as usual ?
You can have multiple logical decoding streams in parallel that track
their position independently of each other. So you can have a logical
replication stream and wal2json next to each other, and they won't
interfere with each other. So what you are considering is possible and
safe. (I don't know whether it will give you satisfactory insights.)
--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services