Checks After Failover Setup
Check Email is Flowing
On (all) the scanner(s) run the following:
tail -f /var/log/mail-daily/current.log
It mail is flowing there should be a flow of log entries, assuming email is coming in. I check for errors or warnings reported in the logs. I also look for entries with either "what=accepted" or "stat=sent". These show CanIt is filtering messages and accepting them for delivery and that message are being successfully sent to the recipient email server.
Checking WAL File Streaming
You can check if WAL data is streaming by running on the primary this command:
watch -d 'ps auxww|grep [s]treaming'
You will see something like this:
postgres 25972 0.2 0.1 103012 4912 ? Ss 15:24 0:09 postgres: wal sender process postgres 192.168.190.120(54248) streaming 26E/6A01AEF0
Where the last few hex digits will be changing if things are okay. (They will change fast on a busy system and possibly very slowly on a lightly-loaded one.)
On the backup database run:
watch -d 'ps auxww| grep "[p]ostgres: startup"'
You should see something like:
postgres 39942 0.0 0.6 101408 27488 ? Ss 15:23 0:02 postgres: startup process recovering 000000070000026E0000006A
Where on a moderately loaded system the last few digits change over very slowly over several minutes. This shows WAL files being consumed.