Log extract showing the above:

INFO eventlet.wsgi.server [None req-5efcaf5b-066e-4a56-a66e-b94f5eae1fd3 demo demo] 172.16.132.149,172.16.132.149 - - [28/Mar/2018 11:36:46] "POST /v2/images/d9293fd1-b558-4cc1-9d3a-68a853f030bd/import HTTP/1.1" 202 211 0.616291
DEBUG glance.api.middleware.version_negotiation [None req-5efcaf5b-066e-4a56-a66e-b94f5eae1fd3 demo demo] Determining version of request: GET /v2/images/d9293fd1-b558-4cc1-9d3a-68a853f030bd Accept: */* {{(pid=97459) process_request /opt/stack/glance/glance/api/middleware/version_negotiation.py:45}}
DEBUG glance.api.middleware.version_negotiation [None req-5efcaf5b-066e-4a56-a66e-b94f5eae1fd3 demo demo] Using url versioning {{(pid=97459) process_request /opt/stack/glance/glance/api/middleware/version_negotiation.py:57}}
DEBUG glance.api.middleware.version_negotiation [None req-5efcaf5b-066e-4a56-a66e-b94f5eae1fd3 demo demo] Matched version: v2 {{(pid=97459) process_request /opt/stack/glance/glance/api/middleware/version_negotiation.py:69}}
DEBUG glance.api.middleware.version_negotiation [None req-5efcaf5b-066e-4a56-a66e-b94f5eae1fd3 demo demo] new path /v2/images/d9293fd1-b558-4cc1-9d3a-68a853f030bd {{(pid=97459) process_request /opt/stack/glance/glance/api/middleware/version_negotiation.py:70}}
INFO glance.domain [-] Task [a2ccc934-b99f-48f6-b99d-b68e294b63d1] status changing from pending to processing
DEBUG glance.async.taskflow_executor [-] Taskflow executor picked up the execution of task ID a2ccc934-b99f-48f6-b99d-b68e294b63d1 of task type api_image_import {{(pid=97459) _run /opt/stack/glance/glance/async/taskflow_executor.py:156}}
DEBUG glance.async.taskflow_executor [-] Flow 'api_image_import' (9ff1df84-4716-4fa3-8160-a8fe938a1482) transitioned into state 'RUNNING' from state 'PENDING' {{(pid=97459) _flow_receiver /usr/local/lib/python2.7/dist-packages/taskflow/listeners/logging.py:145}}
DEBUG glance.async.taskflow_executor [-] Task 'api_image_import-WebDownload-a2ccc934-b99f-48f6-b99d-b68e294b63d1' (16b66c30-7478-4cb3-906c-2250a82d5751) transitioned into state 'RUNNING' from state 'PENDING' {{(pid=97459) _task_receiver /usr/local/lib/python2.7/dist-packages/taskflow/listeners/logging.py:194}}
WARNING glance.async.taskflow_executor [-] Task 'api_image_import-WebDownload-a2ccc934-b99f-48f6-b99d-b68e294b63d1' (16b66c30-7478-4cb3-906c-2250a82d5751) transitioned into state 'FAILURE' from state 'RUNNING'
3 predecessors (most recent first):
  Flow 'api_image_import'
  |__Atom 'api_image_import_retry' {'intention': 'EXECUTE', 'state': 'SUCCESS', 'requires': {}, 'provides': [(None, {})]}
     |__Flow 'api_image_import': Duplicate: Image /opt/stack/data/glance/staging/d9293fd1-b558-4cc1-9d3a-68a853f030bd already exists
ERROR glance.async.taskflow_executor Traceback (most recent call last):
ERROR glance.async.taskflow_executor   File "/usr/local/lib/python2.7/dist-packages/taskflow/engines/action_engine/executor.py", line 53, in _execute_task
ERROR glance.async.taskflow_executor     result = task.execute(**arguments)
ERROR glance.async.taskflow_executor   File "/opt/stack/glance/glance/async/flows/_internal_plugins/web_download.py", line 99, in execute
ERROR glance.async.taskflow_executor     path = self.store.add(self.image_id, data, 0)[0]
ERROR glance.async.taskflow_executor   File "/opt/stack/glance_store/glance_store/capabilities.py", line 225, in op_checker
ERROR glance.async.taskflow_executor     return store_op_fun(store, *args, **kwargs)
ERROR glance.async.taskflow_executor   File "/opt/stack/glance_store/glance_store/_drivers/filesystem.py", line 675, in add
ERROR glance.async.taskflow_executor     raise exceptions.Duplicate(image=filepath)
ERROR glance.async.taskflow_executor Duplicate: Image /opt/stack/data/glance/staging/d9293fd1-b558-4cc1-9d3a-68a853f030bd already exists
ERROR glance.async.taskflow_executor 
DEBUG glance.async.taskflow_executor [-] Task 'api_image_import-WebDownload-a2ccc934-b99f-48f6-b99d-b68e294b63d1' (16b66c30-7478-4cb3-906c-2250a82d5751) transitioned into state 'REVERTING' from state 'FAILURE' {{(pid=97459) _task_receiver /usr/local/lib/python2.7/dist-packages/taskflow/listeners/logging.py:194}}
ERROR glance.async.flows._internal_plugins.web_download [-] Task: a2ccc934-b99f-48f6-b99d-b68e294b63d1 failed to import image d9293fd1-b558-4cc1-9d3a-68a853f030bd to the filesystem.: None
ERROR glance.async.flows._internal_plugins.web_download None
ERROR glance.async.flows._internal_plugins.web_download 
WARNING glance.async.taskflow_executor [-] Task 'api_image_import-WebDownload-a2ccc934-b99f-48f6-b99d-b68e294b63d1' (16b66c30-7478-4cb3-906c-2250a82d5751) transitioned into state 'REVERTED' from state 'REVERTING' with result 'None'
WARNING glance.async.taskflow_executor [-] Flow 'api_image_import' (9ff1df84-4716-4fa3-8160-a8fe938a1482) transitioned into state 'REVERTED' from state 'RUNNING'
ERROR glance.async.taskflow_executor [-] Failed to execute task a2ccc934-b99f-48f6-b99d-b68e294b63d1: Image /opt/stack/data/glance/staging/d9293fd1-b558-4cc1-9d3a-68a853f030bd already exists: Duplicate: Image /opt/stack/data/glance/staging/d9293fd1-b558-4cc1-9d3a-68a853f030bd already exists
INFO glance.domain [-] Task [a2ccc934-b99f-48f6-b99d-b68e294b63d1] status changing from processing to failure
Duplicate: Image /opt/stack/data/glance/staging/d9293fd1-b558-4cc1-9d3a-68a853f030bd already exists