standby on same server as primary

[jl]

Hi, is it possible to create a standby on the same server as the primary?  I am trying to create a local standby that can be paused and resumed. If a certain job fails, we would like to pg_dump from the paused standby and pg_restore into the primary.  once complete, would resume replication.  

1. is this even possible?

2. is this a crazy idea or just crazy enough to work?

3. any other suggestions on how to accomplish this?

Thanks