Nova block migrate will fail if image or snapshot is not available

[Robert van Leeuwen]

When you do a block migration nova checks if the image is in the _base directory.
When the machine does not have the image it will try to download it from Glance.
Since some people throw away unused images and especially snapshots the migration will fail (Traceback, below) when it is not available.
This makes block migration for e.g. maintenance a bit of a headache.

There are 2 possible solutions:
1) A feature that will copy the _base file from the source machine to the target migration machine
2) Add a glance "soft-delete" option so just remove it from the view but actually keep it available for live-migration

2014-02-17 07:51:33.170 27273 ERROR nova.openstack.common.rpc.amqp [req-e5d497d8-16a1-4b0b-82b5-7ea1eba0dcc6 a6f038c720424af48ef4dd3ef6ce86c1 2792c7106e98489da6e38a1ad9ae6685] Exception during message handling
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp Traceback (most recent call last):
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp File "/usr/lib/python2.6/site-packages/nova/openstack/common/rpc/amqp.py", line 461, in _process_data
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp **args)
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp File "/usr/lib/python2.6/site-packages/nova/openstack/common/rpc/dispatcher.py", line 172, in dispatch
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp result = getattr(proxyobj, method)(ctxt, **kwargs)
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp File "/usr/lib/python2.6/site-packages/nova/exception.py", line 90, in wrapped
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp payload)
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp File "/usr/lib/python2.6/site-packages/nova/exception.py", line 73, in wrapped
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp return f(self, context, *args, **kw)
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp File "/usr/lib/python2.6/site-packages/nova/compute/manager.py", line 4067, in live_migration
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp block_migration, migrate_data)
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp File "/usr/lib/python2.6/site-packages/nova/compute/manager.py", line 4059, in live_migration
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp block_migration, disk, dest, migrate_data)
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp File "/usr/lib/python2.6/site-packages/nova/compute/rpcapi.py", line 492, in pre_live_migration
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp disk=disk, migrate_data=migrate_data)
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp File "/usr/lib/python2.6/site-packages/nova/rpcclient.py", line 85, in call
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp return self._invoke(self.proxy.call, ctxt, method, **kwargs)
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp File "/usr/lib/python2.6/site-packages/nova/rpcclient.py", line 63, in _invoke
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp return cast_or_call(ctxt, msg, **self.kwargs)
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp File "/usr/lib/python2.6/site-packages/nova/openstack/common/rpc/proxy.py", line 126, in call
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp result = rpc.call(context, real_topic, msg, timeout)
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp File "/usr/lib/python2.6/site-packages/nova/openstack/common/rpc/__init__.py", line 139, in call
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp return _get_impl().call(CONF, context, topic, msg, timeout)
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp File "/usr/lib/python2.6/site-packages/nova/openstack/common/rpc/impl_kombu.py", line 816, in call
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp rpc_amqp.get_connection_pool(conf, Connection))
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp File "/usr/lib/python2.6/site-packages/nova/openstack/common/rpc/amqp.py", line 574, in call
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp rv = list(rv)
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp File "/usr/lib/python2.6/site-packages/nova/openstack/common/rpc/amqp.py", line 539, in __iter__
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp raise result
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp ImageNotFound_Remote: Image 2b72d644-c346-4ac6-a645-8685fe50e06d could not be found.
2014-02-17 07:51:33.170 27273 TRACE nova.openstack.common.rpc.amqp Traceback (most recent call last):

[David Medberry (med)]

Possibly dupe of bug #1270825 (or visa versa as this is the more generalized case.)