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Display the leader apply worker's PID for parallel apply workers.

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Add leader_pid to pg_stat_subscription. leader_pid is the process ID of
the leader apply worker if this process is a parallel apply worker. If
this field is NULL, it indicates that the process is a leader apply
worker or a synchronization worker. The new column makes it easier to
distinguish parallel apply workers from other kinds of workers and helps
to identify the leader for the parallel workers corresponding to a
particular subscription.

Additionally, update the leader_pid column in pg_stat_activity as well to
display the PID of the leader apply worker for parallel apply workers.

Author: Hou Zhijie
Reviewed-by: Peter Smith, Sawada Masahiko, Amit Kapila, Shveta Mallik
Discussion: https://postgr.es/m/CAA4eK1+wyN6zpaHUkCLorEWNx75MG0xhMwcFhvjqm2KURZEAGw@mail.gmail.com
This commit is contained in:
Amit Kapila
2023-01-18 09:03:12 +05:30
parent 14bdb3f13d
commit d540a02a72
11 changed files with 106 additions and 44 deletions
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3
doc/src/sgml/logical-replication.sgml
View File

@ -1692,7 +1692,8 @@ CONTEXT: processing remote data for replication origin "pg_16395" during "INSER
subscription. A disabled subscription or a crashed subscription will have
zero rows in this view. If the initial data synchronization of any
table is in progress, there will be additional workers for the tables
being synchronized.
being synchronized. Moreover, if the streaming transaction is applied in
parallel, there may be additional parallel apply workers.
</para>
</sect1>

36
doc/src/sgml/monitoring.sgml
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@ -743,9 +743,11 @@ postgres 27093 0.0 0.0 30096 2752 ? Ss 11:34 0:00 postgres: ser
<structfield>leader_pid</structfield> <type>integer</type>
</para>
<para>
Process ID of the parallel group leader, if this process is a
parallel query worker. <literal>NULL</literal> if this process is a
parallel group leader or does not participate in parallel query.
Process ID of the parallel group leader if this process is a parallel
query worker, or process ID of the leader apply worker if this process
is a parallel apply worker. <literal>NULL</literal> indicates that this
process is a parallel group leader or leader apply worker, or does not
participate in any parallel operation.
</para></entry>
</row>
@ -3206,13 +3208,24 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>leader_pid</structfield> <type>integer</type>
</para>
<para>
Process ID of the leader apply worker if this process is a parallel
apply worker; NULL if this process is a leader apply worker or a
synchronization worker
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>relid</structfield> <type>oid</type>
</para>
<para>
OID of the relation that the worker is synchronizing; null for the
main apply worker
OID of the relation that the worker is synchronizing; NULL for the
leader apply worker and parallel apply workers
</para></entry>
</row>
@ -3222,7 +3235,7 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
</para>
<para>
Last write-ahead log location received, the initial value of
this field being 0
this field being 0; NULL for parallel apply workers
</para></entry>
</row>
@ -3231,7 +3244,8 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
<structfield>last_msg_send_time</structfield> <type>timestamp with time zone</type>
</para>
<para>
Send time of last message received from origin WAL sender
Send time of last message received from origin WAL sender; NULL for
parallel apply workers
</para></entry>
</row>
@ -3240,7 +3254,8 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
<structfield>last_msg_receipt_time</structfield> <type>timestamp with time zone</type>
</para>
<para>
Receipt time of last message received from origin WAL sender
Receipt time of last message received from origin WAL sender; NULL for
parallel apply workers
</para></entry>
</row>
@ -3249,7 +3264,8 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
<structfield>latest_end_lsn</structfield> <type>pg_lsn</type>
</para>
<para>
Last write-ahead log location reported to origin WAL sender
Last write-ahead log location reported to origin WAL sender; NULL for
parallel apply workers
</para></entry>
</row>
@ -3259,7 +3275,7 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
</para>
<para>
Time of last write-ahead log location reported to origin WAL
sender
sender; NULL for parallel apply workers
</para></entry>
</row>
</tbody>