ASF GitHub Bot commented on CLOUDSTACK-10326:

blueorangutan commented on issue #2493: CLOUDSTACK-10326: Prevent hosts fall 
into Maintenance when there are running VMs on it
URL: https://github.com/apache/cloudstack/pull/2493#issuecomment-396771363
   @nvazquez a Jenkins job has been kicked to build packages. I'll keep you 
posted as I make progress.

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> 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:
>            Reporter: Nicolas Vazquez
>            Assignee: Nicolas Vazquez
>            Priority: Major
>             Fix For:
>         Attachments: CLOUDSTACK-10326-Debug.png, 
> CLOUDSTACK-10326-InitialState.png, CLOUDSTACK-10326-Migrating.png, 
> CLOUDSTACK-10326-MigrationFailed.png
> 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.
> Screenshots attached, query executed on each case:
> select id, name, instance_name, state, host_id, last_host_id from vm_instance;

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