Re: [GENERAL] BDR node removal and rejoin

 

Found these log entries from one of the other node:

 

t=2017-07-13 08:35:34 PDT p=27292 a=DEBUG:  00000: found valid replication identifier 15

t=2017-07-13 08:35:34 PDT p=27292 a=LOCATION:  bdr_establish_connection_and_slot, bdr.c:604

t=2017-07-13 08:35:34 PDT p=27292 a=ERROR:  53400: no free replication state could be found for 15, increase max_replication_slots

 

Increased max_replication_slots, things are looking good now, thanks.

 

This does bring up a couple of questions:

 

1. Given the fact there is no real increase in the number of nodes in this repeated removal/rejoining exercise, yet it caused replication slots being used up, wouldn’t removal of a node also automatically free up the replication slot allocated for the node?

1. Or is there a way to manually free up no longer needed slots? (the don’t seem to show up in pg_replication_slots view, I made sure to use pg_drop_replication_slot when they do show up there)

1. If there is such a thing, what is the rule of thumb for best value of max_replication_slots (are they somehow related to the value max_wal_senders as well), with respect to, say, the max number of nodes intended to support?