创建物理复制槽:(在master端执行)
postgres=# select pg_create_physical_replication_slot('abce');
删除复制槽：
postgres=# select pg_drop_replication_slot('abce');
1.主库端
(1)查看复制连接的状态
=# select * from pg_stat_replication;
-[ RECORD 1 ]----+------------------------------
pid | 2327
usesysid | 10
usename | mdevan
application_name | walreceiver
client_addr |
client_hostname |
client_port | -1
backend_start | 2022-06-02 06:04:48.536888-04
backend_xmin |
state | streaming
sent_lsn | 0/277628F8
write_lsn | 0/277628F8
flush_lsn | 0/277628F8
replay_lsn | 0/277628F8
write_lag | 00:00:00.000049
flush_lag | 00:00:00.00063
replay_lag | 00:00:00.000662
sync_priority | 0
sync_state | async
-[ RECORD 2 ]----+------------------------------
pid | 2085
usesysid | 10
usename | mdevan
application_name | walreceiver
client_addr |
client_hostname |
client_port | -1
backend_start | 2022-06-02 04:35:36.559838-04
backend_xmin |
state | streaming
sent_lsn | 0/277628F8
write_lsn | 0/277628F8
flush_lsn | 0/277628F8
replay_lsn | 0/277628F8
write_lag |
flush_lag |
replay_lag |
sync_priority | 0
sync_state | async
(2)查看复制槽的状态
pg_replication_slots;
=# select * from pg_replication_slots;
-[ RECORD 1 ]-------+--------------
slot_name | mylogslot
plugin | test_decoding
slot_type | logical
datoid | 16384
database | bench
temporary | f
active | t
active_pid | 2607
xmin |
catalog_xmin | 356948
restart_lsn | 0/3B44A5A0
confirmed_flush_lsn | 0/3B44A5A0
-[ RECORD 2 ]-------+--------------
slot_name | myreplslot1
plugin |
slot_type | physical
datoid |
database |
temporary | f
active | t
active_pid | 2598
xmin |
catalog_xmin |
restart_lsn | 0/3B44A5D8
confirmed_flush_lsn |
2.从库端
(1)日志接收的状态
pg_stat_wal_receiver
=# select * from pg_stat_wal_receiver;
-[ RECORD 1 ]---------+------------------------------
pid | 2084
status | streaming
receive_start_lsn | 0/3000000
receive_start_tli | 1
received_lsn | 0/11233E20
received_tli | 1
last_msg_send_time | 2022-06-02 04:47:53.334477-04
last_msg_receipt_time | 2022-06-02 04:47:53.334519-04
latest_end_lsn | 0/11233E20
latest_end_time | 2022-06-02 04:46:53.261754-04
slot_name |
conninfo | [removed for brevity]
last_msg_receipt_time - last_msg_send_time 表示复制wal接收的延迟；这里slot_name的值为空，表示没有使用复制槽。
这个就是使用复制槽的例子：
=# select * from pg_stat_wal_receiver;
-[ RECORD 1 ]---------+------------------------------
pid | 2326
status | streaming
receive_start_lsn | 0/15000000
receive_start_tli | 1
received_lsn | 0/15000060
received_tli | 1
last_msg_send_time | 2022-06-02 06:04:48.537842-04
last_msg_receipt_time | 2022-06-02 06:04:48.537887-04
latest_end_lsn | 0/15000060
latest_end_time | 2022-06-02 06:04:48.537842-04
slot_name | myreplslot1
conninfo | [removed for brevity]
(2)日志应用状态
pg_last_wal_receive_lsn(), pg_last_wal_replay_lsn()查看从库日志应用的状态
=# select pg_last_wal_receive_lsn(), pg_last_wal_replay_lsn(), pg_last_xact_replay_timestamp();
-[ RECORD 1 ]-----------------+------------------------------
pg_last_wal_receive_lsn | 0/1A000000
pg_last_wal_replay_lsn | 0/19FFE928
pg_last_xact_replay_timestamp | 2022-06-02 06:13:42.141768-04
pg_last_wal_replay_lsn - pg_last_wal_receive_lsn 表示日志应用的延迟。
推荐使用工具pgmetrics查看
其它
#主库端执行
select pid,
application_name,
pg_wal_lsn_diff(pg_current_wal_lsn(), sent_lsn) sending_lag,
pg_wal_lsn_diff(sent_lsn, flush_lsn) receiving_lag,
pg_wal_lsn_diff(flush_lsn, replay_lsn) replaying_lag,
pg_wal_lsn_diff(pg_current_wal_lsn(), replay_lsn) total_lag
from pg_stat_replication;
#从库端执行
SELECT CASE
WHEN pg_last_wal_receive_lsn() = pg_last_wal_replay_lsn() THEN
0
ELSE
EXTRACT(EPOCH FROM now() - pg_last_xact_replay_timestamp())
END AS log_delay,
pg_last_wal_receive_lsn(),
pg_last_wal_replay_lsn(),
pg_last_xact_replay_timestamp();