Basic Ruby script to listen for Postgres notifications from a central database and update a client database.

listen.rb

require 'rubygems'
require 'sequel'
require 'json'
require 'pg'

DB_central = Sequel.connect('postgres://xxx:xxx@hostname/central_db')
DB_client1 = Sequel.connect('postgres://xxx:xxx@hostname/client1_db')

DB_central.listen :usersupdate, {loop: true} do |channel, pid, payload|

puts "#{channel} -- #{pid} -- #{payload}"

j = JSON.parse(payload)

if j && j["id"]
DB_client1.
 from(:users).
 where(id: j["id"]).
 update(email: j["email"], name: j["name"])
end