Обсуждение: Logical Replication Setup using one replication slot per table?
Hi all; I setup logical replication by specifying 402 specific tables like shown below: On the Publisher: CREATE PUBLICATION testpub FOR TABLE my_test_schema.core_tab_00, my_test_schema.core_tab_01, -- and more tables my_test_schema.core_tab_401, my_test_schema.core_tab_402 ; On the Subscriber: CREATE SUBSCRIPTION testsub connection 'host=10.10.10.7 dbname=my_test_db port=5432' PUBLICATION testpub; Once I started replication I was seeing errors in the log on the subscriber about not enough replication slots, it seems the db wants to create a replication slot for each table, I grabbed all the rows with "could not create replication slot" and parsed the set to a unique list and came up with 385 rows like these: ERROR: could not create replication slot "pg_92884_sync_85377_7213515424408371294": ERROR: all replication slots are in use As I continue checking the number of unique "could not create replication slot" entries in the log is growing I have max_replication_slots on both servers set to 10 If i run this query on the publisher I see 10 rows: # select * from pg_stat_replication_slots ; slot_name | spill_txns | spill_count | spill_bytes | stream_txns | stream_count | stream_bytes | total_txns | total_bytes | stats_reset -----------------------------------------+------------+-------------+-------------+-------------+--------------+--------------+------------+-------------+------------- testsub2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | pg_92884_sync_81493_7213515424408371294 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | pg_92884_sync_71976_7213515424408371294 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | pg_92884_sync_72306_7213515424408371294 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | pg_92884_sync_71760_7213515424408371294 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | pg_92884_sync_74101_7213515424408371294 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | pg_92884_sync_74661_7213515424408371294 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | pg_92884_sync_71286_7213515424408371294 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | pg_92884_sync_82949_7213515424408371294 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | pg_92884_sync_81829_7213515424408371294 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | (10 rows) It seems that PostgreSQL wants to create a replication slot for each table, I did a test on a separate set of VMs before this with 50 tables and it only used one replication slot, what is going on? Am I doing something wrong?
I found the answer in the Docs:
Each subscription will receive changes via one replication slot (see Section 27.2.6). Additional replication slots may be required for the initial data synchronization of pre-existing table data and those will be dropped at the end of data synchronization.
Which is exactly the behavior I saw
On 3/22/23 17:57, Sbob wrote:
Hi all;
I setup logical replication by specifying 402 specific tables like shown below:
On the Publisher:
CREATE PUBLICATION testpub FOR TABLE
my_test_schema.core_tab_00,
my_test_schema.core_tab_01,
-- and more tables
my_test_schema.core_tab_401,
my_test_schema.core_tab_402
;
On the Subscriber:
CREATE SUBSCRIPTION testsub
connection 'host=10.10.10.7 dbname=my_test_db port=5432' PUBLICATION testpub;
Once I started replication I was seeing errors in the log on the subscriber about not enough replication slots, it seems the db wants to create a replication slot for each table, I grabbed all the rows with "could not create replication slot" and parsed the set to a unique list and came up with 385 rows like these:
ERROR: could not create replication slot "pg_92884_sync_85377_7213515424408371294": ERROR: all replication slots are in use
As I continue checking the number of unique "could not create replication slot" entries in the log is growing
I have max_replication_slots on both servers set to 10
If i run this query on the publisher I see 10 rows:
# select * from pg_stat_replication_slots ;
slot_name | spill_txns | spill_count | spill_bytes | stream_txns | stream_count | stream_bytes | total_txns | total_bytes | stats_reset
-----------------------------------------+------------+-------------+-------------+-------------+--------------+--------------+------------+-------------+-------------
testsub2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
pg_92884_sync_81493_7213515424408371294 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
pg_92884_sync_71976_7213515424408371294 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
pg_92884_sync_72306_7213515424408371294 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
pg_92884_sync_71760_7213515424408371294 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
pg_92884_sync_74101_7213515424408371294 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
pg_92884_sync_74661_7213515424408371294 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
pg_92884_sync_71286_7213515424408371294 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
pg_92884_sync_82949_7213515424408371294 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
pg_92884_sync_81829_7213515424408371294 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
(10 rows)
It seems that PostgreSQL wants to create a replication slot for each table, I did a test on a separate set of VMs before this with 50 tables and it only used one replication slot, what is going on? Am I doing something wrong?