[Kimchi-devel] [PATCH 2/3 v2] Live migration backend: control/vms and model/vms changes

[Aline Manera]

On 28/10/2015 15:41, dhbarboza82 at gmail.com wrote:
> From: Daniel Henrique Barboza <dhbarboza82 at gmail.com>
>
> This patch adds the backend code to support live (and cold) migration
> in Kimchi.
>
> Signed-off-by: Daniel Henrique Barboza <dhbarboza82 at gmail.com>
> ---
>   src/wok/plugins/kimchi/control/vms.py |  3 ++
>   src/wok/plugins/kimchi/model/vms.py   | 73 ++++++++++++++++++++++++++++++++++-
>   2 files changed, 75 insertions(+), 1 deletion(-)
>
> diff --git a/src/wok/plugins/kimchi/control/vms.py b/src/wok/plugins/kimchi/control/vms.py
> index 58d4b67..5e24538 100644
> --- a/src/wok/plugins/kimchi/control/vms.py
> +++ b/src/wok/plugins/kimchi/control/vms.py
> @@ -49,6 +49,9 @@ class VM(Resource):
>                                                     destructive=True)
>           self.connect = self.generate_action_handler('connect')
>           self.clone = self.generate_action_handler_task('clone')
> +        self.migrate = self.generate_action_handler_task('migrate',
> +                                                         ['remote_host',
> +                                                          'user'])
>           self.suspend = self.generate_action_handler('suspend')
>           self.resume = self.generate_action_handler('resume')
>
> diff --git a/src/wok/plugins/kimchi/model/vms.py b/src/wok/plugins/kimchi/model/vms.py
> index 60145d0..e90b5ed 100644
> --- a/src/wok/plugins/kimchi/model/vms.py
> +++ b/src/wok/plugins/kimchi/model/vms.py
> @@ -36,7 +36,7 @@ from wok.exception import NotFoundError, OperationFailed
>   from wok.model.tasks import TaskModel
>   from wok.rollbackcontext import RollbackContext
>   from wok.utils import add_task, convert_data_size, get_next_clone_name
> -from wok.utils import import_class, run_setfacl_set_attr, wok_log
> +from wok.utils import import_class, run_setfacl_set_attr, run_command, wok_log
>   from wok.xmlutils.utils import xpath_get_text, xml_item_update
>   from wok.xmlutils.utils import dictize
>
> @@ -1294,6 +1294,77 @@ class VMModel(object):
>               raise OperationFailed('KCHVM0040E', {'name': name,
>                                                    'err': e.message})
>
> +    def _check_if_host_not_localhost(self, remote_host):
> +        hostname, _, returncode = run_command(['hostname'], 5, silent=True)
> +

Please, use the python API to get the system hostname

 >>> import socket
 >>> socket.gethostname()
'alinefm-ThinkPad-T440'


> +        if returncode != 0:
> +            raise OperationFailed("KCHVM0061E", {'host': remote_host})
> +
> +        if remote_host in ['localhost', '127.0.0.1', hostname]:
> +            raise OperationFailed("KCHVM0055E", {'host': remote_host})
> +
> +    def _check_if_password_less_login_enabled(self, remote_host, user):
> +        username_host = "%s@%s" % (user, remote_host)
> +        ssh_cmd = ['ssh', '-oNumberOfPasswordPrompts=0',
> +                   '-oStrictHostKeyChecking=no', username_host,
> +                   'echo', 'hello']
> +        stdout, stderr, returncode = run_command(ssh_cmd, 5, silent=True)
> +        if returncode != 0:
> +            raise OperationFailed("KCHVM0056E",
> +                                  {'host': remote_host, 'user': user})
> +
> +    def _get_remote_libvirt_conn(self, remote_host,
> +                                 user='root', transport='ssh'):
> +        dest_uri = 'qemu+%s://%s@%s/system' % (transport, user, remote_host)
> +        # TODO: verify why LibvirtConnection(dest_uri) does not work here
> +        return libvirt.open(dest_uri)
> +
> +    def migration_pre_check(self, remote_host, user):
> +        self._check_if_host_not_localhost(remote_host)
> +        self._check_if_password_less_login_enabled(remote_host, user)
> +
> +    def migrate(self, name, remote_host, user='root'):
> +        name = name.decode('utf-8')
> +        remote_host = remote_host.decode('utf-8')
> +
> +        self.migration_pre_check(remote_host, user)
> +        dest_conn = self._get_remote_libvirt_conn(remote_host)
> +
> +        params = {'name': name,
> +                  'dest_conn': dest_conn}
> +        task_id = add_task('/vms/%s/migrate' % name, self._migrate_task,
> +                           self.objstore, params)
> +
> +        return self.task.lookup(task_id)
> +
> +    def _migrate_task(self, cb, params):
> +        name = params['name'].decode('utf-8')
> +        dest_conn = params['dest_conn']
> +
> +        cb('starting a migration')
> +
> +        dom = self.get_vm(name, self.conn)
> +        state = DOM_STATE_MAP[dom.info()[0]]
> +
> +        flags = libvirt.VIR_MIGRATE_PEER2PEER
> +        if state == 'shutoff':
> +            flags |= (libvirt.VIR_MIGRATE_OFFLINE |
> +                      libvirt.VIR_MIGRATE_PERSIST_DEST)
> +        elif state in ['running', 'paused']:
> +            flags |= libvirt.VIR_MIGRATE_LIVE | libvirt.VIR_MIGRATE_TUNNELLED
> +            if dom.isPersistent():
> +                flags |= libvirt.VIR_MIGRATE_PERSIST_DEST
> +        else:
> +            raise OperationFailed("KCHVM0057E", {'name': name,
> +                                                 'state': state})
> +        try:
> +            dom.migrate(dest_conn, flags)
> +        except libvirt.libvirtError as e:
> +            cb('Migrate failed', False)
> +            raise OperationFailed('KCHVM0058E', {'err': e.message,
> +                                                 'name': name})
> +        cb('Migrate finished', True)
> +

Remember to close the libvirt connection 'dest_conn' to avoid problem 
with memory leak. =)

>   class VMScreenshotModel(object):
>       def __init__(self, **kargs):