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Introduce a new GUC 'standby_slot_names'.

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This patch provides a way to ensure that physical standbys that are
potential failover candidates have received and flushed changes before
the primary server making them visible to subscribers. Doing so guarantees
that the promoted standby server is not lagging behind the subscribers
when a failover is necessary.

The logical walsender now guarantees that all local changes are sent and
flushed to the standby servers corresponding to the replication slots
specified in 'standby_slot_names' before sending those changes to the
subscriber.

Additionally, the SQL functions pg_logical_slot_get_changes,
pg_logical_slot_peek_changes and pg_replication_slot_advance are modified
to ensure that they process changes for failover slots only after physical
slots specified in 'standby_slot_names' have confirmed WAL receipt for those.

Author: Hou Zhijie and Shveta Malik
Reviewed-by: Masahiko Sawada, Peter Smith, Bertrand Drouvot, Ajin Cherian, Nisha Moond, Amit Kapila
Discussion: https://postgr.es/m/514f6f2f-6833-4539-39f1-96cd1e011f23@enterprisedb.com
This commit is contained in:
Amit Kapila
2024-03-08 08:10:45 +05:30
parent 453c468737
commit bf279ddd1c
18 changed files with 918 additions and 27 deletions
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1
src/backend/utils/activity/wait_event_names.txt
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@@ -78,6 +78,7 @@ GSS_OPEN_SERVER "Waiting to read data from the client while establishing a GSSAP
LIBPQWALRECEIVER_CONNECT "Waiting in WAL receiver to establish connection to remote server."
LIBPQWALRECEIVER_RECEIVE "Waiting in WAL receiver to receive data from remote server."
SSL_OPEN_SERVER "Waiting for SSL while attempting connection."
WAIT_FOR_STANDBY_CONFIRMATION "Waiting for WAL to be received and flushed by the physical standby."
WAL_SENDER_WAIT_FOR_WAL "Waiting for WAL to be flushed in WAL sender process."
WAL_SENDER_WRITE_DATA "Waiting for any activity when processing replies from WAL receiver in WAL sender process."

14
src/backend/utils/misc/guc_tables.c
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@@ -4670,6 +4670,20 @@ struct config_string ConfigureNamesString[] =
check_debug_io_direct, assign_debug_io_direct, NULL
},
{
{"standby_slot_names", PGC_SIGHUP, REPLICATION_PRIMARY,
gettext_noop("Lists streaming replication standby server slot "
"names that logical WAL sender processes will wait for."),
gettext_noop("Logical WAL sender processes will send decoded "
"changes to plugins only after the specified "
"replication slots confirm receiving WAL."),
GUC_LIST_INPUT
},
&standby_slot_names,
"",
check_standby_slot_names, assign_standby_slot_names, NULL
},
/* End-of-list marker */
{
{NULL, 0, 0, NULL, NULL}, NULL, NULL, NULL, NULL, NULL

2
src/backend/utils/misc/postgresql.conf.sample
View File

@@ -343,6 +343,8 @@
# method to choose sync standbys, number of sync standbys,
# and comma-separated list of application_name
# from standby(s); '*' = all
#standby_slot_names = '' # streaming replication standby server slot names that
# logical walsender processes will wait for
# - Standby Servers -