all_connections_reconnect.rb

pools = ActiveRecord::Base.connection_handler.connection_pools.values
pools.each do |pool|
  pool.connections.each{|connection| connection.reconnect!}
end

test_code.rb

# Meanwhile, in rails console...
employer_ids = Employer.where(db_host: 0).limit(10).pluck(:id)
employer_ids << Employer.where(db_host: 1).limit(10).pluck(:id)
employer_ids << Employer.where(db_host: 2).limit(10).pluck(:id)
employer_ids.flatten!

500.times{Resque.enqueue_to(:A, DBTickler, 200, 0.05, *employer_ids)}