When adding a new host, and foreman fails to query the authoritative dns server(s), you get a full failure below. Should this error be a little more descriptive? It's quite difficult to understand that a dns query simply failed. (in our case, the firewall was blocking the request)

Started POST "/hosts" for 192.168.100.46 at Tue May 21 09:19:49 -0500 2013
Processing by HostsController#create as
Parameters: {"host"=>{"build"=>"1", "compute_attributes"=>{"volumes_attributes"=>{"0"=>{"_delete"=>"", "name"=>"Hard disk", "size_gb"=>"20", "datastore"=>"DEV-NFS-VMDK-DATA1"}, "new_volumes"=>{"_delete"=>"", "name"=>"Hard disk", "size_gb"=>"10", "datastore"=>"DEV-NFS-VMDK-DATA1"}}, "path"=>"/Datacenters/Dev/vm/DEV.LAB", "memory_mb"=>"768", "start"=>"1", "cpus"=>"1", "cluster"=>"Dev General Use", "interfaces_attributes"=>{"new_interfaces"=>{"_delete"=>"", "network"=>"Dev VM 10.10.40.0"}, "0"=>{"_delete"=>"", "network"=>"Dev VM 10.10.40.0"}}}, "updated_at"=>"1369145851", "root_pass"=>"[FILTERED]", "puppet_proxy_id"=>"2", "ip"=>"10.10.40.233", "provision_method"=>"build", "ptable_id"=>"11", "managed"=>"true", "progress_report_id"=>"[FILTERED]", "compute_resource_id"=>"1", "domain_id"=>"1", "medium_id"=>"6", "disk"=>"", "comment"=>"", "name"=>"devt-bus-jnk001", "environment_id"=>"4", "model_id"=>"", "mac"=>"", "subnet_id"=>"2", "enabled"=>"1", "overwrite"=>"false", "puppetclass_ids"=>[""], "interfaces_attributes"=>{"new_interfaces"=>{"_destroy"=>"false", "ip"=>"", "domain_id"=>"1", "provider"=>"IPMI", "name"=>"", "mac"=>"", "type"=>"Nic::Managed"}}, "operatingsystem_id"=>"1", "hostgroup_id"=>"44", "architecture_id"=>"1"}, "authenticity_token"=>"AZhLndXgF2yMN3eV4iddK8sUQ2DKKnumvKW6lgG9aps=", "capabilities"=>"build", "utf8"=>"✓"}
User Load (1.2ms) SELECT `users`.* FROM `users` WHERE `users`.`id` = 1 LIMIT 1
Setting current user thread-local variable to admin
SQL (1.3ms) BEGIN
SQL (1.1ms) COMMIT
SQL (0.7ms) BEGIN
Hostgroup Load (0.8ms) SELECT `hostgroups`.* FROM `hostgroups` WHERE `hostgroups`.`id` = 44 AND (1=1) LIMIT 1
Environment Load (1.8ms) SELECT `environments`.* FROM `environments` WHERE `environments`.`id` = 4 ORDER BY environments.name LIMIT 1
Domain Load (2.3ms) SELECT `domains`.* FROM `domains` WHERE `domains`.`id` = 1 ORDER BY LOWER LIMIT 1
SmartProxy Load (1.7ms) SELECT `smart_proxies`.* FROM `smart_proxies` WHERE `smart_proxies`.`id` = 2 ORDER BY LOWER LIMIT 1
CACHE (0.0ms) SELECT `smart_proxies`.* FROM `smart_proxies` WHERE `smart_proxies`.`id` = 2 ORDER BY LOWER LIMIT 1
Operatingsystem Load (2.3ms) SELECT `operatingsystems`.* FROM `operatingsystems` WHERE `operatingsystems`.`id` = 1 ORDER BY LOWER LIMIT 1
Architecture Load (2.0ms) SELECT `architectures`.* FROM `architectures` WHERE `architectures`.`id` = 1 LIMIT 1
ComputeResource Load (2.1ms) SELECT `compute_resources`.* FROM `compute_resources` WHERE `compute_resources`.`id` = 1 ORDER BY LOWER LIMIT 1
Medium Load (1.3ms) SELECT `media`.* FROM `media` WHERE `media`.`id` = 6 ORDER BY LOWER LIMIT 1
Ptable Load (3.4ms) SELECT `ptables`.* FROM `ptables` WHERE `ptables`.`id` = 11 ORDER BY LOWER LIMIT 1
Subnet Load (0.7ms) SELECT `subnets`.* FROM `subnets` WHERE `subnets`.`id` = 2 ORDER BY vlanid LIMIT 1
Setting Load (0.7ms) SELECT `settings`.* FROM `settings` WHERE `settings`.`name` = 'use_uuid_for_certificates' ORDER BY LOWER LIMIT 1
SQL (1.6ms) SELECT 1 FROM `hosts` WHERE (`hosts`.`name` = BINARY 'devt-bus-jnk001.dev.lab') LIMIT 1
SmartProxy Load (0.8ms) SELECT `smart_proxies`.* FROM `smart_proxies` WHERE `smart_proxies`.`id` = 11 ORDER BY LOWER LIMIT 1
SQL (0.9ms) SELECT 1 FROM `hosts` WHERE (`hosts`.`ip` = BINARY '10.10.40.233') LIMIT 1
Scheduling new DHCP reservations for devt-bus-jnk001.dev.lab
SmartProxy Load (1.4ms) SELECT `smart_proxies`.* FROM `smart_proxies` WHERE `smart_proxies`.`id` = 10 ORDER BY LOWER LIMIT 1
Setting Load (0.9ms) SELECT `settings`.* FROM `settings` WHERE `settings`.`name` = 'query_local_nameservers' ORDER BY LOWER LIMIT 1
SQL (1.3ms) ROLLBACK
Operation FAILED: #<Net::Error:0x7f672259cff0>
/usr/share/foreman/lib/net/dns.rb:36:in `lookup'
/usr/share/foreman/lib/net/dns.rb:61:in `dns_lookup'
/usr/share/foreman/lib/net/dns/a_record.rb:28:in `conflicts'
/usr/share/foreman/lib/net.rb:27:in `conflicting?'
/usr/share/foreman/app/models/orchestration/dns.rb:124:in `dns_conflict_detected?'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/callbacks.rb:456:in `_run_validation_callbacks'
/usr/share/foreman/vendor/ruby/1.8/gems/activemodel-3.0.20/lib/active_model/validations/callbacks.rb:67:in `run_validations!'
/usr/share/foreman/vendor/ruby/1.8/gems/activemodel-3.0.20/lib/active_model/validations.rb:179:in `valid?'
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.20/lib/active_record/validations.rb:55:in `valid?'
/usr/share/foreman/app/models/orchestration.rb:50:in `valid?'
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.20/lib/active_record/validations.rb:75:in `perform_validations'
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.20/lib/active_record/validations.rb:43:in `save'
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.20/lib/active_record/attribute_methods/dirty.rb:21:in `save'
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.20/lib/active_record/transactions.rb:240:in `save'
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.20/lib/active_record/transactions.rb:292:in `with_transaction_returning_status'
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.20/lib/active_record/connection_adapters/abstract/database_statements.rb:139:in `transaction'
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.20/lib/active_record/transactions.rb:207:in `transaction'
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.20/lib/active_record/transactions.rb:290:in `with_transaction_returning_status'
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.20/lib/active_record/transactions.rb:240:in `save'
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.20/lib/active_record/transactions.rb:251:in `rollback_active_record_state!'
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.20/lib/active_record/transactions.rb:239:in `save'
/usr/share/foreman/app/controllers/hosts_controller.rb:89:in `create'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_controller/metal/implicit_render.rb:4:in `send_action'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_controller/metal/implicit_render.rb:4:in `send_action'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/abstract_controller/base.rb:150:in `process_action'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_controller/metal/rendering.rb:11:in `process_action'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/abstract_controller/callbacks.rb:18:in `process_action'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/callbacks.rb:469:in `_run__1151525278__process_action__764201132__callbacks'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/callbacks.rb:221:in `_conditional_callback_around_4431'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/callbacks.rb:331:in `around'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/callbacks.rb:315:in `send'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/callbacks.rb:315:in `_callback_around_1458'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/callbacks.rb:220:in `_conditional_callback_around_4431'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/callbacks.rb:468:in `_run__1151525278__process_action__764201132__callbacks'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/callbacks.rb:221:in `_conditional_callback_around_4430'
/usr/share/foreman/lib/foreman/thread_session.rb:31:in `clear_thread'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/callbacks.rb:220:in `_conditional_callback_around_4430'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/callbacks.rb:437:in `_run__1151525278__process_action__764201132__callbacks'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/callbacks.rb:221:in `_conditional_callback_around_4429'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/callbacks.rb:331:in `around'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/callbacks.rb:315:in `send'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/callbacks.rb:315:in `_callback_around_13'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/callbacks.rb:220:in `_conditional_callback_around_4429'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/callbacks.rb:436:in `_run__1151525278__process_action__764201132__callbacks'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/callbacks.rb:410:in `send'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/callbacks.rb:410:in `_run_process_action_callbacks'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/callbacks.rb:94:in `send'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/callbacks.rb:94:in `run_callbacks'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/abstract_controller/callbacks.rb:17:in `process_action'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_controller/metal/rescue.rb:17:in `process_action'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_controller/metal/instrumentation.rb:30:in `process_action'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/notifications.rb:52:in `instrument'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/notifications/instrumenter.rb:21:in `instrument'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/notifications.rb:52:in `instrument'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_controller/metal/instrumentation.rb:29:in `process_action'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/abstract_controller/base.rb:119:in `process'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/abstract_controller/rendering.rb:41:in `process'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_controller/metal.rb:138:in `dispatch'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_controller/metal.rb:178:in `action'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_dispatch/routing/route_set.rb:68:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_dispatch/routing/route_set.rb:68:in `dispatch'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_dispatch/routing/route_set.rb:33:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/rack-mount-0.6.14/lib/rack/mount/route_set.rb:148:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/rack-mount-0.6.14/lib/rack/mount/code_generation.rb:93:in `recognize'
/usr/share/foreman/vendor/ruby/1.8/gems/rack-mount-0.6.14/lib/rack/mount/code_generation.rb:229:in `optimized_each'
/usr/share/foreman/vendor/ruby/1.8/gems/rack-mount-0.6.14/lib/rack/mount/code_generation.rb:92:in `recognize'
/usr/share/foreman/vendor/ruby/1.8/gems/rack-mount-0.6.14/lib/rack/mount/route_set.rb:139:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_dispatch/routing/route_set.rb:499:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/apipie-rails-0.0.13/lib/apipie/static_dispatcher.rb:57:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_dispatch/middleware/head.rb:14:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/rack-1.2.8/lib/rack/methodoverride.rb:24:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_dispatch/middleware/params_parser.rb:21:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_dispatch/middleware/flash.rb:182:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_dispatch/middleware/session/abstract_store.rb:149:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_dispatch/middleware/cookies.rb:302:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.20/lib/active_record/query_cache.rb:32:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.20/lib/active_record/connection_adapters/abstract/query_cache.rb:28:in `cache'
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.20/lib/active_record/query_cache.rb:12:in `cache'
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.20/lib/active_record/query_cache.rb:31:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.20/lib/active_record/connection_adapters/abstract/connection_pool.rb:354:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_dispatch/middleware/callbacks.rb:46:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/callbacks.rb:416:in `_run_call_callbacks'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_dispatch/middleware/callbacks.rb:44:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/rack-1.2.8/lib/rack/sendfile.rb:106:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_dispatch/middleware/remote_ip.rb:48:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_dispatch/middleware/show_exceptions.rb:47:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/railties-3.0.20/lib/rails/rack/logger.rb:13:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/rack-1.2.8/lib/rack/runtime.rb:17:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.20/lib/active_support/cache/strategy/local_cache.rb:72:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/rack-1.2.8/lib/rack/lock.rb:13:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/rack-1.2.8/lib/rack/lock.rb:13:in `synchronize'
/usr/share/foreman/vendor/ruby/1.8/gems/rack-1.2.8/lib/rack/lock.rb:13:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.20/lib/action_dispatch/middleware/static.rb:30:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/railties-3.0.20/lib/rails/application.rb:168:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/railties-3.0.20/lib/rails/application.rb:77:in `send'
/usr/share/foreman/vendor/ruby/1.8/gems/railties-3.0.20/lib/rails/application.rb:77:in `method_missing'
/usr/share/foreman/vendor/ruby/1.8/gems/rack-1.2.8/lib/rack/urlmap.rb:47:in `call'
/usr/share/foreman/vendor/ruby/1.8/gems/rack-1.2.8/lib/rack/urlmap.rb:41:in `each'
/usr/share/foreman/vendor/ruby/1.8/gems/rack-1.2.8/lib/rack/urlmap.rb:41:in `call'
/usr/lib/ruby/1.8/phusion_passenger/rack/request_handler.rb:92:in `process_request'
/usr/lib/ruby/1.8/phusion_passenger/abstract_request_handler.rb:207:in `main_loop'
/usr/lib/ruby/1.8/phusion_passenger/rack/application_spawner.rb:118:in `run'
/usr/lib/ruby/1.8/phusion_passenger/rack/application_spawner.rb:65:in `spawn_application'
/usr/lib/ruby/1.8/phusion_passenger/utils.rb:184:in `safe_fork'
/usr/lib/ruby/1.8/phusion_passenger/rack/application_spawner.rb:58:in `spawn_application'
/usr/lib/ruby/1.8/phusion_passenger/rack/application_spawner.rb:41:in `spawn_application'
/usr/lib/ruby/1.8/phusion_passenger/spawn_manager.rb:159:in `spawn_application'
/usr/lib/ruby/1.8/phusion_passenger/spawn_manager.rb:287:in `handle_spawn_application'
/usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:352:in `__send__'
/usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:352:in `main_loop'
/usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:196:in `start_synchronously'
/usr/lib/phusion_passenger/passenger-spawn-server:61
Rendered common/500.rhtml (4.0ms)
Completed 500 Internal Server Error in 3221ms (Views: 8.1ms | ActiveRecord: 32.1ms)