Nicolas Vazquez created CLOUDSTACK-10326:
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Summary: Prevent hosts fall into Maintenance when there are
running VMs on it
Key: CLOUDSTACK-10326
URL: https://issues.apache.org/jira/browse/CLOUDSTACK-10326
Project: CloudStack
Issue Type: Bug
Security Level: Public (Anyone can view this level - this is the default.)
Affects Versions: 4.11.0.0
Reporter: Nicolas Vazquez
Assignee: Nicolas Vazquez
Fix For: 4.11.1.0
This issue was discovered, fixed and tested on KVM, but applies for every
hypervisor.
h2. Background
When enabling maintenance mode in a host, host state is put into
'PrepareForMaintenance' and running VMs are migrated into another host. After
every VM is migrated, host goes to 'Maintenance' state.
Checks are performed on ResourceManagerImpl.checkAndMaintan() method:
* List VMs with host_id = HOST_ID
* List VMs with last_host_id = HOST_ID and state=Migrating
When both queries are empty, then the host can be put into Maintenance.
When a VM is being migrated to DEST_HOST, its host_id column is set to
DEST_HOST, last_host_id = ORIGIN_HOST and state = Migrating. If then migration
fails, host_id = last_host_id = ORIGIN_HOST
h2. Issue
This sequence:
* Enable maintenance mode on ORIGIN_HOST
* VMs start being migrated to a host, say DEST_HOST
* checkAndMaintain() starts:
** First check passes (no VM with host_id = ORIGIN_HOST_ID as those are being
migrated)
** Before the second check, one or more migrations fail
** Second check passes, however there are VMs running on the host as
migrations have failed.
* Host goes into Maintenance state.
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