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[Bug 1706750] Re: FlushError for automatic IPAllocations when subnet create is retried

To: yahoo-eng-team@xxxxxxxxxxxxxxxxxxx
From: OpenStack Infra <1706750@xxxxxxxxxxxxxxxxxx>
Date: Mon, 31 Jul 2017 23:25:31 -0000
Reply-to: Bug 1706750 <1706750@xxxxxxxxxxxxxxxxxx>
Sender: bounces@xxxxxxxxxxxxx
Reviewed:  https://review.openstack.org/485328
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=d207fb92354858e7443113a4b5d642a465a3af27
Submitter: Jenkins
Branch:    master

commit d207fb92354858e7443113a4b5d642a465a3af27
Author: Ihar Hrachyshka <ihrachys@xxxxxxxxxx>
Date:   Wed Jul 19 11:56:55 2017 -0700

    Fixed FlushError on subnet creation retry
    
    Automatically allocated fixed IP addresses were not reflected on cached
    port records, which triggered FlushError if the allocating method failed
    and triggered a retry.
    
    Change-Id: Ia7725094827b554aa6d928c7daa026959a237991
    Closes-Bug: #1706750


** Changed in: neutron
       Status: In Progress => Fix Released

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https://bugs.launchpad.net/bugs/1706750

Title:
  FlushError for automatic IPAllocations when subnet create is retried

Status in neutron:
  Fix Released

Bug description:
  The error is seen in Red Hat CI: https://bugzilla.redhat.com/show_bug.cgi?id=1470784
  There are hits in Kibana too: http://logstash.openstack.org/#dashboard/file/logstash.json?query=message%3A%5C%22FlushError%3A%20New%20instance%20%3CIPAllocation%20at%5C%22

  In server.log:

  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation [req-3c97d83e-3beb-4b28-a29f-697fc1ee8bc6 5f2e0d72ef8e4fb18b500759cfe5e503 205f2a3630a0426f8da20b4467ea003b - default default] POST failed.: FlushError: New instance <IPAllocation at 0x8b3f7d0> with identity key (<class 'neutron.db.models_v2.IPAllocation'>, ('2003::1:f816:3eff:fe3f:aa00', '8032a1cd-9236-4126-83fa-2f039ed2b890', 'c0542b84-bcd0-48e1-ace1-6da1f50246dc')) conflicts with persistent instance <IPAllocation at 0x89ac310>
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation Traceback (most recent call last):
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/pecan/core.py", line 678, in __call__
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     self.invoke_controller(controller, args, kwargs, state)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/pecan/core.py", line 569, in invoke_controller
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     result = controller(*args, **kwargs)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/db/api.py", line 94, in wrapped
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     setattr(e, '_RETRY_EXCEEDED', True)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 220, in __exit__
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     self.force_reraise()
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 196, in force_reraise
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     six.reraise(self.type_, self.value, self.tb)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/db/api.py", line 90, in wrapped
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     return f(*args, **kwargs)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_db/api.py", line 150, in wrapper
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     ectxt.value = e.inner_exc
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 220, in __exit__
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     self.force_reraise()
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 196, in force_reraise
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     six.reraise(self.type_, self.value, self.tb)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_db/api.py", line 138, in wrapper
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     return f(*args, **kwargs)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/db/api.py", line 129, in wrapped
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     LOG.debug("Retry wrapper got retriable exception: %s", e)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 220, in __exit__
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     self.force_reraise()
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 196, in force_reraise
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     six.reraise(self.type_, self.value, self.tb)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/db/api.py", line 125, in wrapped
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     return f(*dup_args, **dup_kwargs)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/pecan_wsgi/controllers/utils.py", line 70, in wrapped
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     return f(*args, **kwargs)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/pecan_wsgi/controllers/resource.py", line 152, in post
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     return self.create(resources)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/pecan_wsgi/controllers/resource.py", line 170, in create
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     return {key: creator(*creator_args, **creator_kwargs)}
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/common/utils.py", line 665, in inner
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     return f(self, context, *args, **kwargs)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/db/api.py", line 164, in wrapped
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     return method(*args, **kwargs)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/db/api.py", line 94, in wrapped
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     setattr(e, '_RETRY_EXCEEDED', True)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 220, in __exit__
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     self.force_reraise()
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 196, in force_reraise
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     six.reraise(self.type_, self.value, self.tb)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/db/api.py", line 90, in wrapped
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     return f(*args, **kwargs)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_db/api.py", line 150, in wrapper
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     ectxt.value = e.inner_exc
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 220, in __exit__
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     self.force_reraise()
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 196, in force_reraise
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     six.reraise(self.type_, self.value, self.tb)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_db/api.py", line 138, in wrapper
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     return f(*args, **kwargs)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/db/api.py", line 129, in wrapped
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     LOG.debug("Retry wrapper got retriable exception: %s", e)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 220, in __exit__
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     self.force_reraise()
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 196, in force_reraise
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     six.reraise(self.type_, self.value, self.tb)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/db/api.py", line 125, in wrapped
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     return f(*dup_args, **dup_kwargs)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/plugins/ml2/plugin.py", line 985, in create_subnet
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     result, mech_context = self._create_subnet_db(context, subnet)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/plugins/ml2/plugin.py", line 977, in _create_subnet_db
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     self._create_subnet_postcommit(context, result, net_db, ipam_sub)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/db/api.py", line 164, in wrapped
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     return method(*args, **kwargs)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/db/api.py", line 94, in wrapped
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     setattr(e, '_RETRY_EXCEEDED', True)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 220, in __exit__
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     self.force_reraise()
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 196, in force_reraise
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     six.reraise(self.type_, self.value, self.tb)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/db/api.py", line 90, in wrapped
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     return f(*args, **kwargs)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_db/api.py", line 150, in wrapper
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     ectxt.value = e.inner_exc
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 220, in __exit__
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     self.force_reraise()
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 196, in force_reraise
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     six.reraise(self.type_, self.value, self.tb)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_db/api.py", line 138, in wrapper
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     return f(*args, **kwargs)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/db/api.py", line 129, in wrapped
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     LOG.debug("Retry wrapper got retriable exception: %s", e)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 220, in __exit__
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     self.force_reraise()
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 196, in force_reraise
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     six.reraise(self.type_, self.value, self.tb)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/db/api.py", line 125, in wrapped
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     return f(*dup_args, **dup_kwargs)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/db/db_base_plugin_v2.py", line 675, in _create_subnet_postcommit
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     result, ipam_subnet)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/db/ipam_pluggable_backend.py", line 491, in add_auto_addrs_on_network_ports
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     allocated.create()
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/objects/base.py", line 225, in decorator
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     res = func(self, *args, **kwargs)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/objects/base.py", line 632, in create
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     self.modify_fields_to_db(fields))
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib/python2.7/site-packages/neutron/objects/db/api.py", line 61, in create_object
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     context.session.add(db_obj)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib64/python2.7/site-packages/sqlalchemy/orm/session.py", line 567, in __exit__
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     self.rollback()
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib64/python2.7/site-packages/sqlalchemy/util/langhelpers.py", line 66, in __exit__
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     compat.reraise(exc_type, exc_value, exc_tb)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib64/python2.7/site-packages/sqlalchemy/orm/session.py", line 564, in __exit__
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     self.commit()
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib64/python2.7/site-packages/sqlalchemy/orm/session.py", line 461, in commit
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     self._prepare_impl()
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib64/python2.7/site-packages/sqlalchemy/orm/session.py", line 441, in _prepare_impl
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     self.session.flush()
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib64/python2.7/site-packages/sqlalchemy/orm/session.py", line 2171, in flush
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     self._flush(objects)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib64/python2.7/site-packages/sqlalchemy/orm/session.py", line 2291, in _flush
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     transaction.rollback(_capture_exception=True)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib64/python2.7/site-packages/sqlalchemy/util/langhelpers.py", line 66, in __exit__
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     compat.reraise(exc_type, exc_value, exc_tb)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib64/python2.7/site-packages/sqlalchemy/orm/session.py", line 2255, in _flush
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     flush_context.execute()
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib64/python2.7/site-packages/sqlalchemy/orm/unitofwork.py", line 389, in execute
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     rec.execute(self)
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib64/python2.7/site-packages/sqlalchemy/orm/unitofwork.py", line 548, in execute
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     uow
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib64/python2.7/site-packages/sqlalchemy/orm/persistence.py", line 156, in save_obj
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     base_mapper, states, uowtransaction
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation   File "/usr/lib64/python2.7/site-packages/sqlalchemy/orm/persistence.py", line 312, in _organize_states_for_save
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation     state_str(existing)))
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation FlushError: New instance <IPAllocation at 0x8b3f7d0> with identity key (<class 'neutron.db.models_v2.IPAllocation'>, ('2003::1:f816:3eff:fe3f:aa00', '8032a1cd-9236-4126-83fa-2f039ed2b890', 'c0542b84-bcd0-48e1-ace1-6da1f50246dc')) conflicts with persistent instance <IPAllocation at 0x89ac310>
  2017-07-13 15:20:51.064 85185 ERROR neutron.pecan_wsgi.hooks.translation

  Just before the traceback, we see retry triggered by StaleDataError:

  2017-07-13 15:20:50.668 85185 DEBUG neutron.db.api [req-3c97d83e-3beb-4b28-a29f-697fc1ee8bc6 5f2e0d72ef8e4fb18b500759cfe5e503 205f2a3630a0426f8da20b4467ea003b - default default] Retry wrapper got retriable exception: UPDATE statement on table 'standardattributes' expected to update 1 row(s); 0 were matched. wrapped /usr/lib/python2.7/site-packages/neutron/db/api.py:129
  2017-07-13 15:20:50.669 85185 DEBUG oslo_db.api [req-3c97d83e-3beb-4b28-a29f-697fc1ee8bc6 5f2e0d72ef8e4fb18b500759cfe5e503 205f2a3630a0426f8da20b4467ea003b - default default] Performing DB retry for function neutron.db.db_base_plugin_v2._create_subnet_postcommit wrapper /usr/lib/python2.7/site-packages/oslo_db/api.py:152

  This is probably related to https://review.openstack.org/#/c/396718/

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https://bugs.launchpad.net/neutron/+bug/1706750/+subscriptions
References

[Bug 1706750] [NEW] FlushError for automatic IPAllocations when subnet create is retried
From: Ihar Hrachyshka, 2017-07-26