Strange Error to create Host with API and oVirt

When I run the POST method with this json (In Foreman GUI the host is
created easily):

String jsonText = "{"host": {" +
""name": "prova2","+ //'host_ovirt'
""hostgroup_id": 1,"+
""operatingsystem_id": 1," +
""environment_id": " + environmentid + "," +
//""architecture_id": 1," +
//""domain_id": 1," +
""mac": ""," +
""compute_resource_id": "7"," +//7
""ptable_id":"11"," +
""build": 1,"+
""enabled": 1,"+ //0
""managed": 1,"+
""compute_attributes": {"+
""cpus": 1,"+ //1
""cluster": "Provisioning","+ //'Provisioning'
""start": 0,"+ //0
""path": "/Datacenters/xxx","+
""memory_mb": 512"+ //256
"}"+
"}"+
"}";
I always get the same error:

{"errors":["Failed to create a compute ovirt (oVirt) instance
prova2.res.eng.it: \n
/usr/share/foreman/vendor/ruby/1.8/gems/rbovirt-0.0.16/lib/rbovirt.rb:146:in
handle_fault'\n /usr/share/foreman/vendor/ruby/1.8/gems/rbovirt-0.0.16/lib/rbovirt.rb:89:inhttp_post'\n
/usr/share/foreman/vendor/ruby/1.8/gems/rbovirt-0.0.16/lib/client/vm_api.rb:35:in
create_vm'\n /usr/share/foreman/vendor/ruby/1.8/gems/fog-1.9.0/lib/fog/ovirt/requests/compute/create_vm.rb:7:increate_vm'\n
/usr/share/foreman/vendor/ruby/1.8/gems/fog-1.9.0/lib/fog/ovirt/models/compute/server.rb:122:in
save'\n /usr/share/foreman/vendor/ruby/1.8/gems/fog-1.9.0/lib/fog/core/collection.rb:52:increate'\n /usr/share/foreman/app/models/compute_resource.rb:108:in
create_vm'\n /usr/share/foreman/lib/foreman/model/ovirt.rb:79:increate_vm'\n
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.15/lib/active_record/associations/association_proxy.rb:227:in
send'\n /usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.15/lib/active_record/associations/association_proxy.rb:227:inmethod_missing'\n
/usr/share/foreman/app/models/orchestration/compute.rb:59:in setCompute'\n /usr/share/foreman/app/models/orchestration.rb:156:insend'\n
/usr/share/foreman/app/models/orchestration.rb:156:in execute'\n /usr/share/foreman/app/models/orchestration.rb:96:inprocess'\n
/usr/share/foreman/app/models/orchestration.rb:88:in each'\n /usr/share/foreman/app/models/orchestration.rb:88:inprocess'\n
/usr/share/foreman/app/models/orchestration.rb:33:in on_save'\n /usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.15/lib/active_support/callbacks.rb:515:in_run_save_callbacks'\n
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.15/lib/active_record/callbacks.rb:273:in
create_or_update'\n /usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.15/lib/active_record/persistence.rb:40:insave'\n
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.15/lib/active_record/validations.rb:43:in
save'\n /usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.15/lib/active_record/attribute_methods/dirty.rb:21:insave'\n
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.15/lib/active_record/transactions.rb:240:in
save'\n /usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.15/lib/active_record/transactions.rb:292:inwith_transaction_returning_status'\n
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.15/lib/active_record/connection_adapters/abstract/database_statements.rb:139:in
transaction'\n /usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.15/lib/active_record/transactions.rb:207:intransaction'\n
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.15/lib/active_record/transactions.rb:290:in
with_transaction_returning_status'\n /usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.15/lib/active_record/transactions.rb:240:insave'\n
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.15/lib/active_record/transactions.rb:251:in
rollback_active_record_state!'\n /usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.15/lib/active_record/transactions.rb:239:insave'\n /usr/share/foreman/app/controllers/hosts_controller.rb:89:in
create'\n /usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_controller/metal/implicit_render.rb:4:insend_action'\n
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_controller/metal/implicit_render.rb:4:in
send_action'\n /usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/abstract_controller/base.rb:150:inprocess_action'\n
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_controller/metal/rendering.rb:11:in
process_action'\n /usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/abstract_controller/callbacks.rb:18:inprocess_action'\n
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.15/lib/active_support/callbacks.rb:466:in
_run__1055050562__process_action__449529386__callbacks'\n /usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.15/lib/active_support/callbacks.rb:221:in_conditional_callback_around_3103'\n
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.15/lib/active_support/callbacks.rb:331:in
around'\n /usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.15/lib/active_support/callbacks.rb:315:insend'\n
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.15/lib/active_support/callbacks.rb:315:in
_callback_around_13'\n /usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.15/lib/active_support/callbacks.rb:220:in_conditional_callback_around_3103'\n
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.15/lib/active_support/callbacks.rb:436:in
_run__1055050562__process_action__449529386__callbacks'\n /usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.15/lib/active_support/callbacks.rb:410:insend'\n
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.15/lib/active_support/callbacks.rb:410:in
_run_process_action_callbacks'\n /usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.15/lib/active_support/callbacks.rb:94:insend'\n
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.15/lib/active_support/callbacks.rb:94:in
run_callbacks'\n /usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/abstract_controller/callbacks.rb:17:inprocess_action'\n
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_controller/metal/rescue.rb:17:in
process_action'\n /usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_controller/metal/instrumentation.rb:30:inprocess_action'\n
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.15/lib/active_support/notifications.rb:52:in
instrument'\n /usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.15/lib/active_support/notifications/instrumenter.rb:21:ininstrument'\n
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.15/lib/active_support/notifications.rb:52:in
instrument'\n /usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_controller/metal/instrumentation.rb:29:inprocess_action'\n
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/abstract_controller/base.rb:119:in
process'\n /usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/abstract_controller/rendering.rb:41:inprocess'\n
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_controller/metal.rb:138:in
dispatch'\n /usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_controller/metal/rack_delegation.rb:14:indispatch'\n
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_controller/metal.rb:178:in
action'\n /usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_dispatch/routing/route_set.rb:68:incall'\n
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_dispatch/routing/route_set.rb:68:in
dispatch'\n /usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_dispatch/routing/route_set.rb:33:incall'\n
/usr/share/foreman/vendor/ruby/1.8/gems/rack-mount-0.6.14/lib/rack/mount/route_set.rb:148:in
call'\n /usr/share/foreman/vendor/ruby/1.8/gems/rack-mount-0.6.14/lib/rack/mount/code_generation.rb:93:inrecognize'\n
/usr/share/foreman/vendor/ruby/1.8/gems/rack-mount-0.6.14/lib/rack/mount/code_generation.rb:208:in
optimized_each'\n /usr/share/foreman/vendor/ruby/1.8/gems/rack-mount-0.6.14/lib/rack/mount/code_generation.rb:92:inrecognize'\n
/usr/share/foreman/vendor/ruby/1.8/gems/rack-mount-0.6.14/lib/rack/mount/route_set.rb:139:in
call'\n /usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_dispatch/routing/route_set.rb:499:incall'\n
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_dispatch/middleware/best_standards_support.rb:17:in
call'\n /usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_dispatch/middleware/head.rb:14:incall'\n
/usr/share/foreman/vendor/ruby/1.8/gems/rack-1.2.7/lib/rack/methodoverride.rb:24:in
call'\n /usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_dispatch/middleware/params_parser.rb:21:incall'\n
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_dispatch/middleware/flash.rb:182:in
call'\n /usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_dispatch/middleware/session/abstract_store.rb:149:incall'\n
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_dispatch/middleware/cookies.rb:302:in
call'\n /usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.15/lib/active_record/query_cache.rb:32:incall'\n
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.15/lib/active_record/connection_adapters/abstract/query_cache.rb:28:in
cache'\n /usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.15/lib/active_record/query_cache.rb:12:incache'\n
/usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.15/lib/active_record/query_cache.rb:31:in
call'\n /usr/share/foreman/vendor/ruby/1.8/gems/activerecord-3.0.15/lib/active_record/connection_adapters/abstract/connection_pool.rb:354:incall'\n
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_dispatch/middleware/callbacks.rb:46:in
call'\n /usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.15/lib/active_support/callbacks.rb:416:in_run_call_callbacks'\n
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_dispatch/middleware/callbacks.rb:44:in
call'\n /usr/share/foreman/vendor/ruby/1.8/gems/rack-1.2.7/lib/rack/sendfile.rb:106:incall'\n
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_dispatch/middleware/remote_ip.rb:48:in
call'\n /usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_dispatch/middleware/show_exceptions.rb:47:incall'\n
/usr/share/foreman/vendor/ruby/1.8/gems/railties-3.0.15/lib/rails/rack/logger.rb:13:in
call'\n /usr/share/foreman/vendor/ruby/1.8/gems/rack-1.2.7/lib/rack/runtime.rb:17:incall'\n
/usr/share/foreman/vendor/ruby/1.8/gems/activesupport-3.0.15/lib/active_support/cache/strategy/local_cache.rb:72:in
call'\n /usr/share/foreman/vendor/ruby/1.8/gems/rack-1.2.7/lib/rack/lock.rb:13:incall'\n
/usr/share/foreman/vendor/ruby/1.8/gems/rack-1.2.7/lib/rack/lock.rb:13:in
synchronize'\n /usr/share/foreman/vendor/ruby/1.8/gems/rack-1.2.7/lib/rack/lock.rb:13:incall'\n
/usr/share/foreman/vendor/ruby/1.8/gems/actionpack-3.0.15/lib/action_dispatch/middleware/static.rb:30:in
call'\n /usr/share/foreman/vendor/ruby/1.8/gems/railties-3.0.15/lib/rails/application.rb:168:incall'\n
/usr/share/foreman/vendor/ruby/1.8/gems/railties-3.0.15/lib/rails/application.rb:77:in
send'\n /usr/share/foreman/vendor/ruby/1.8/gems/railties-3.0.15/lib/rails/application.rb:77:inmethod_missing'\n
/usr/share/foreman/vendor/ruby/1.8/gems/rack-1.2.7/lib/rack/urlmap.rb:47:in
call'\n /usr/share/foreman/vendor/ruby/1.8/gems/rack-1.2.7/lib/rack/urlmap.rb:41:ineach'\n
/usr/share/foreman/vendor/ruby/1.8/gems/rack-1.2.7/lib/rack/urlmap.rb:41:in
call'\n /usr/lib/ruby/1.8/phusion_passenger/rack/request_handler.rb:92:inprocess_request'\n
/usr/lib/ruby/1.8/phusion_passenger/abstract_request_handler.rb:207:in
main_loop'\n /usr/lib/ruby/1.8/phusion_passenger/rack/application_spawner.rb:118:inrun'\n
/usr/lib/ruby/1.8/phusion_passenger/rack/application_spawner.rb:65:in
spawn_application'\n /usr/lib/ruby/1.8/phusion_passenger/utils.rb:184:insafe_fork'\n
/usr/lib/ruby/1.8/phusion_passenger/rack/application_spawner.rb:58:in
spawn_application'\n /usr/lib/ruby/1.8/phusion_passenger/rack/application_spawner.rb:41:inspawn_application'\n
/usr/lib/ruby/1.8/phusion_passenger/spawn_manager.rb:159:in
spawn_application'\n /usr/lib/ruby/1.8/phusion_passenger/spawn_manager.rb:287:inhandle_spawn_application'\n
/usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:352:in __send__'\n /usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:352:inmain_loop'\n
/usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:196:in
`start_synchronously'\n
/usr/lib/phusion_passenger/passenger-spawn-server:61"]}

Maybe the error is in path field or cluster field where I pass the cluster
names configured in oVirt (cluster : "Provisioning") and the datacenter
("/datacenter/xxx") configured in oVirt where xxx corrisponding at the
datacenter id. Is this correct or not?

How can I solve it? Thanks all for your large support.