Hi guys,
I've got some database servers in USA (own data center) and also @ AWS
Japan.
*USA:*
master01
slave01 (Streaming Replication from master01 + wal_files)
slave02 (Streaming Replication from master01 + wal_files)
*Japan: (Cascading replication)*
slave03 (Streaming Replication from slave02 + wal_files)
slave04 (Streaming Replication from slave02)
*Running this query on slave02:*
select now() - pg_last_xact_replay_timestamp() AS replication_delay;
replication_delay
-------------------
00:00:00.802012
(1 row)
*Same query on slave03 and slave04:*
select now() - pg_last_xact_replay_timestamp() AS replication_delay;
replication_delay
-------------------
00:56:53.639516
(1 row)
*slave02:*
SELECT client_hostname , client_addr ,
pg_xlog_location_diff(pg_stat_replication.sent_location,
pg_stat_replication.replay_location) AS byte_lag FROM pg_stat_replication;
client_hostname | client_addr | byte_lag
-----------------+---------------+----------
| slave03 | 2097400
| slave04 | 3803888
(2 rows)
Why is that delay that big? Is it because networking issue? I tried to find
out what the cause is, but couldn't find anything.
SCP and FTP (big files) between those servers are really fast, +1.0MB/s.
I'm using PostgreSQL 9.2.14
Thanks!
Patrick.
