Postgresql – Postgres slave max_connections = master’s max_connections

Check out repmrg:

repmgr is a set of open source tools that helps DBAs and System administrators manage a cluster of PostgreSQL databases..

By taking advantage of the Hot Standby capability introduced in PostgreSQL 9, repmgr greatly simplifies the process of setting up and managing database with high availability and scalability requirements.

repmgr simplifies administration and daily management, enhances productivity and reduces the overall costs of a PostgreSQL cluster by:

• monitoring the replication process; allowing DBAs to issue high
• availability operations such as switch-overs and fail-overs.

It does two things:

1. repmgr: command program that performs tasks on your cluster and then exits
2. repmgrd: management and monitoring daemon that watches the cluster and can automate remote actions.

For automatic failover, repmgrd does the trick and is not a SPOF in your network, like pgPool. However, it is still important to monitor all deamons and bring them back up after failure.

Version 2.0 is about to be released, including RPM's.

The answer is yes. What is actually happening is that the slave receives binary patch files and applies those. It is slightly complicated but in general your slave can be offline temporarily and then later catch up. I would imagine that there are limits in the amount of time that can pass but in the event that it falls too far behind you can use WAL segments to catch up (as I understand it, unarchived wal segments are the primary key here, so if you pass the point where you need archived segments to catch up, you will need those segments accessible via log shipping or the like).