dineshbhor 25d33d2cb1 Fix race condition between evacuation and its confirmation ... Masakari can face a race condition where after evacuation of an instance to other host user might perform some actions on that instance which gives wrong instance vm_state to ConfirmEvacuationTask that results into notification failure. To fix this issue this patch proposes to lock the instance before evacuation till its confirmation so that any normal user will not be able to perform any actions on it. To achieve this the ConfirmEvacuationTask is completly removed and the confirmation is done in the EvacuateInstancesTask itself by per instance. Evacuating an instance and confirming it's evacuation immediately can reduce the performance so this patch uses the eventlet.greenpool.GreenPool which executes the complete evacuation and confirmation of an instance in a separate thread. To check if the server is already locked or not upgraded the novaclient's NOVA_API_VERSION from 2.1 to 2.9 as the 'locked' property is available in nova api_version 2.9 and above. This patch introduces a new config option 'host_failure_recovery_threads' which will be the number of threads to be used for evacuating and confirming the instances evacuation. The default value for this config option is 3. Closes-Bug: #1693728 Change-Id: Ib5145878633fd424bca5bcbd5cfed13d20362f94		2017-06-23 13:08:03 +05:30
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notes	Fix race condition between evacuation and its confirmation	2017-06-23 13:08:03 +05:30
source	Fix release notes formatting	2017-02-15 12:18:25 +05:30