The local database configuration deployed by the puppet_compiler puppet module is no longer working under puppetdb 4. According to the puppet docs the subprotocol setting used to specify hsqldb is now ignored by puppetdb and the only mentioned backend is postgres. https://puppet.com/docs/puppetdb/4.4/configure.html#subprotocol
This is probably a good opportunity to move puppet compiler over to the role/profile paradigm as well. We could create a profile::puppet_compiler separate profile for a postgres backed puppet-compiler to deploy puppetdb4 compilers in parallel.