we observe similar behavior as described here: https://projects.theforeman.org/issues/25140

• there are discovered unprovisioned hosts present in the list
• The user with non-admin permissions try to create a "new host" (so discovery hosts are not even touched! )

the error message is

Invalid single-table inheritance type: Host::Discovered is not a subclass of Host::Managed

if the list of "discovered" hosts is empty. this problem does not hit. (so the user creating a host just fine.)

We are on 1.18.2. Organizations are disabled.

full stack trace:

ActiveRecord::SubclassNotFound
Invalid single-table inheritance type: Host::Discovered is not a subclass of Host::Managed
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/inheritance.rb:203:in `find_sti_class'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/inheritance.rb:177:in `discriminate_class_for_record'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/persistence.rb:67:in `instantiate'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/querying.rb:50:in `block (2 levels) in find_by_sql'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/result.rb:55:in `block in each'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/result.rb:55:in `each'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/result.rb:55:in `each'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/querying.rb:50:in `map'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/querying.rb:50:in `block in find_by_sql'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activesupport-5.1.6/lib/active_support/notifications/instrumenter.rb:21:in `instrument'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/querying.rb:49:in `find_by_sql'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/relation.rb:678:in `exec_queries'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/relation.rb:546:in `load'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/relation.rb:255:in `records'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/relation/delegation.rb:39:in `each'
/usr/share/foreman/app/services/authorizer_cache.rb:12:in `include?'
/usr/share/foreman/app/services/authorizer_cache.rb:12:in `collection_cache_lookup'
/usr/share/foreman/app/services/authorizer.rb:20:in `can?'
/usr/share/foreman/app/models/concerns/authorizable.rb:12:in `check_permissions_after_save'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activesupport-5.1.6/lib/active_support/callbacks.rb:413:in `block in make_lambda'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activesupport-5.1.6/lib/active_support/callbacks.rb:235:in `block in halting_and_conditional'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activesupport-5.1.6/lib/active_support/callbacks.rb:511:in `block in invoke_after'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activesupport-5.1.6/lib/active_support/callbacks.rb:511:in `each'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activesupport-5.1.6/lib/active_support/callbacks.rb:511:in `invoke_after'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activesupport-5.1.6/lib/active_support/callbacks.rb:122:in `block in run_callbacks'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activesupport-5.1.6/lib/active_support/callbacks.rb:135:in `run_callbacks'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activesupport-5.1.6/lib/active_support/callbacks.rb:827:in `_run_save_callbacks'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/callbacks.rb:336:in `create_or_update'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/persistence.rb:129:in `save'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/validations.rb:44:in `save'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/attribute_methods/dirty.rb:35:in `save'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/transactions.rb:308:in `block (2 levels) in save'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/transactions.rb:384:in `block in with_transaction_returning_status'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/connection_adapters/abstract/database_statements.rb:235:in `block in transaction'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/connection_adapters/abstract/transaction.rb:194:in `block in within_new_transaction'
/opt/rh/rh-ruby24/root/usr/share/ruby/monitor.rb:214:in `mon_synchronize'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/connection_adapters/abstract/transaction.rb:191:in `within_new_transaction'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/connection_adapters/abstract/database_statements.rb:235:in `transaction'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/transactions.rb:210:in `transaction'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/transactions.rb:381:in `with_transaction_returning_status'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/transactions.rb:308:in `block in save'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/transactions.rb:323:in `rollback_active_record_state!'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/transactions.rb:307:in `save'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/suppressor.rb:42:in `save'
/usr/share/foreman/app/models/concerns/foreman/sti.rb:26:in `save'
/usr/share/foreman/app/controllers/hosts_controller.rb:104:in `create'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/action_controller/metal/basic_implicit_render.rb:4:in `send_action'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/abstract_controller/base.rb:186:in `process_action'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/action_controller/metal/rendering.rb:30:in `process_action'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/abstract_controller/callbacks.rb:20:in `block in process_action'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activesupport-5.1.6/lib/active_support/callbacks.rb:108:in `block in run_callbacks'
/usr/share/foreman/app/controllers/concerns/application_shared.rb:15:in `set_timezone'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activesupport-5.1.6/lib/active_support/callbacks.rb:117:in `block in run_callbacks'
/usr/share/foreman/app/models/concerns/foreman/thread_session.rb:32:in `clear_thread'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activesupport-5.1.6/lib/active_support/callbacks.rb:117:in `block in run_callbacks'
/usr/share/foreman/app/controllers/concerns/foreman/controller/topbar_sweeper.rb:12:in `set_topbar_sweeper_controller'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activesupport-5.1.6/lib/active_support/callbacks.rb:117:in `block in run_callbacks'
/opt/theforeman/tfm/root/usr/share/gems/gems/audited-4.7.0/lib/audited/sweeper.rb:14:in `around'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activesupport-5.1.6/lib/active_support/callbacks.rb:117:in `block in run_callbacks'
/opt/theforeman/tfm/root/usr/share/gems/gems/audited-4.7.0/lib/audited/sweeper.rb:14:in `around'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activesupport-5.1.6/lib/active_support/callbacks.rb:117:in `block in run_callbacks'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activesupport-5.1.6/lib/active_support/callbacks.rb:135:in `run_callbacks'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/abstract_controller/callbacks.rb:19:in `process_action'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/action_controller/metal/rescue.rb:20:in `process_action'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/action_controller/metal/instrumentation.rb:32:in `block in process_action'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activesupport-5.1.6/lib/active_support/notifications.rb:166:in `block in instrument'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activesupport-5.1.6/lib/active_support/notifications/instrumenter.rb:21:in `instrument'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activesupport-5.1.6/lib/active_support/notifications.rb:166:in `instrument'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/action_controller/metal/instrumentation.rb:30:in `process_action'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/action_controller/metal/params_wrapper.rb:252:in `process_action'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/railties/controller_runtime.rb:22:in `process_action'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/abstract_controller/base.rb:124:in `process'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionview-5.1.6/lib/action_view/rendering.rb:30:in `process'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/action_controller/metal.rb:189:in `dispatch'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/action_controller/metal.rb:253:in `dispatch'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/action_dispatch/routing/route_set.rb:49:in `dispatch'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/action_dispatch/routing/route_set.rb:31:in `serve'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/action_dispatch/journey/router.rb:50:in `block in serve'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/action_dispatch/journey/router.rb:33:in `each'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/action_dispatch/journey/router.rb:33:in `serve'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/action_dispatch/routing/route_set.rb:844:in `call'
/opt/theforeman/tfm/root/usr/share/gems/gems/apipie-rails-0.5.9/lib/apipie/static_dispatcher.rb:65:in `call'
/opt/theforeman/tfm/root/usr/share/gems/gems/apipie-rails-0.5.9/lib/apipie/extractor/recorder.rb:136:in `call'
/usr/share/foreman/lib/middleware/telemetry.rb:9:in `call'
/opt/theforeman/tfm/root/usr/share/gems/gems/apipie-rails-0.5.9/lib/apipie/middleware/checksum_in_headers.rb:27:in `call'
/usr/share/foreman/lib/middleware/catch_json_parse_errors.rb:8:in `call'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/rack-2.0.3/lib/rack/etag.rb:25:in `call'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/rack-2.0.3/lib/rack/conditional_get.rb:38:in `call'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/rack-2.0.3/lib/rack/head.rb:12:in `call'
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/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/rack-2.0.3/lib/rack/session/abstract/id.rb:232:in `context'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/rack-2.0.3/lib/rack/session/abstract/id.rb:226:in `call'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/action_dispatch/middleware/cookies.rb:613:in `call'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/action_dispatch/middleware/callbacks.rb:26:in `block in call'
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/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/action_dispatch/middleware/callbacks.rb:24:in `call'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/action_dispatch/middleware/debug_exceptions.rb:59:in `call'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/action_dispatch/middleware/show_exceptions.rb:31:in `call'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/railties-5.1.6/lib/rails/rack/logger.rb:36:in `call_app'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/railties-5.1.6/lib/rails/rack/logger.rb:26:in `call'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/sprockets-rails-3.2.1/lib/sprockets/rails/quiet_assets.rb:13:in `call'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/action_dispatch/middleware/remote_ip.rb:79:in `call'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/actionpack-5.1.6/lib/action_dispatch/middleware/request_id.rb:25:in `call'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/rack-2.0.3/lib/rack/method_override.rb:22:in `call'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/rack-2.0.3/lib/rack/runtime.rb:22:in `call'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activesupport-5.1.6/lib/active_support/cache/strategy/local_cache_middleware.rb:27:in `call'
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/opt/theforeman/tfm/root/usr/share/gems/gems/secure_headers-5.0.5/lib/secure_headers/middleware.rb:13:in `call'
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/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/railties-5.1.6/lib/rails/railtie.rb:185:in `public_send'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/railties-5.1.6/lib/rails/railtie.rb:185:in `method_missing'
/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/rack-2.0.3/lib/rack/urlmap.rb:68:in `block in call'
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/opt/theforeman/tfm-ror51/root/usr/share/gems/gems/rack-2.0.3/lib/rack/urlmap.rb:53:in `call'
/usr/share/passenger/phusion_passenger/rack/thread_handler_extension.rb:74:in `process_request'
/usr/share/passenger/phusion_passenger/request_handler/thread_handler.rb:141:in `accept_and_process_next_request'
/usr/share/passenger/phusion_passenger/request_handler/thread_handler.rb:109:in `main_loop'
/usr/share/passenger/phusion_passenger/request_handler.rb:455:in `block (3 levels) in start_threads'
/opt/theforeman/tfm/root/usr/share/gems/gems/logging-2.2.2/lib/logging/diagnostic_context.rb:474:in `block in create_with_logging_context'