Jak správně nastavit Postgres Streaming replication

Zdravím, Provozuji pár postgresů v konfuguraci master -> Streaming replication slave, ale nejsem si jistý zda je vše nastaveno správně.

Pokud se na slave zeptám opakovaně na "SELECT CASE WHEN pg_last_xlog_receive_location() = pg_last_xlog_replay_location() THEN 0 ELSE EXTRACT (EPOCH FROM now() - pg_last_xact_replay_timestamp()) END AS log_delay;" dostanu toto:

postgres=# SELECT extract(seconds from (now() - pg_last_xact_replay_timestamp())) AS time_lag;
 time_lag 
----------
 6.465722
(1 row)

postgres=# SELECT extract(seconds from (now() - pg_last_xact_replay_timestamp())) AS time_lag;
 time_lag 
----------
 0.905263
(1 row)

postgres=# SELECT extract(seconds from (now() - pg_last_xact_replay_timestamp())) AS time_lag;
 time_lag 
----------
 2.105338
(1 row)

postgres=# SELECT extract(seconds from (now() - pg_last_xact_replay_timestamp())) AS time_lag;
 time_lag 
----------
 3.225638
(1 row)

postgres=# SELECT extract(seconds from (now() - pg_last_xact_replay_timestamp())) AS time_lag;
 time_lag 
----------
 4.210284
(1 row)

postgres=# SELECT extract(seconds from (now() - pg_last_xact_replay_timestamp())) AS time_lag;
 time_lag 
----------
 5.066044
(1 row)

postgres=# SELECT extract(seconds from (now() - pg_last_xact_replay_timestamp())) AS time_lag;
 time_lag 
----------
 5.930428
(1 row)

postgres=# SELECT extract(seconds from (now() - pg_last_xact_replay_timestamp())) AS time_lag;
 time_lag 
----------
 6.708723
(1 row)

postgres=# SELECT extract(seconds from (now() - pg_last_xact_replay_timestamp())) AS time_lag;
 time_lag 
----------
 0.068862
(1 row)

V příloze je pak jal to vypadá v monitoringu. V postgresql.conf mám ( na slave) na konci nastaveno toto.

   
    wal_level = hot_standby
    full_page_writes = on
    wal_log_hints = on
    max_wal_senders = 6
    max_replication_slots = 6
    hot_standby = on
    hot_standby_feedback = on

Otázkou tedy je zda je to nastaveno správně a proč dochází k lagu aplikování WAL na slave. Neuměl by mi někdo poradit zda je to takto správně, a pokud není, tak jak to nastavit?

Dotaz: Jak správně nastavit Postgres Streaming replication

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