[openstack-dev] [nova] nova boot from image created volume

Matt Riedemann mriedemos at gmail.com
Thu Apr 6 16:18:17 UTC 2017


On 4/6/2017 10:05 AM, Jay Pipes wrote:
>> jaypipes at serialcoder:~/src/git.openstack.org/openstack/nova/nova$
>> ack-grep --ignore-dir tests --ignore-dir locale "volume_api.create"
>> compute/api.py
>> 2982:                snapshot = self.volume_api.create_snapshot_force(
>>
>> api/openstack/compute/volumes.py
>> 185:            new_volume = self.volume_api.create(
>> 582:            create_func = self.volume_api.create_snapshot_force
>> 584:            create_func = self.volume_api.create_snapshot
>>
>> virt/block_device.py
>> 63:    :returns: The availability_zone value to pass to volume_api.create
>> 487:            vol = volume_api.create(context, self.volume_size, '',
>> '',
>> 508:            vol = volume_api.create(context, self.volume_size,
>> 530:            vol = volume_api.create(context, self.volume_size,
>> vol_name, '',
>
> Best,
> -jay
>
> On 04/06/2017 03:29 AM, 李田清 wrote:
>> Hello,
>>     If we use nova boot from image and created volume, i think the
>> nova will
>>     use volume/cinder.py:create to create volume. But after insert pdb,
>> i do not find
>>     the specific code of line to call the create. Can someone help me to
>> point out the
>>     code of the line? Thanks a lot.
>>
>>
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For the case you're looking for, the volume is created here:

https://github.com/openstack/nova/blob/8d9bf947a4c8654a30e016a5d95d9bec55447506/nova/virt/block_device.py#L508

That happens when the compute manager is preparing block devices to 
attach to the instance while building it on the compute host.

After the volume is created and nova gets the volume ID back, we wait 
for it to be available before we can attach it:

https://github.com/openstack/nova/blob/8d9bf947a4c8654a30e016a5d95d9bec55447506/nova/virt/block_device.py#L512

Which uses this function passed in from the compute manager (yes, it's 
gross tight coupling):

https://github.com/openstack/nova/blob/8d9bf947a4c8654a30e016a5d95d9bec55447506/nova/compute/manager.py#L1221

And finally it attaches the volume to the instance via a call to the 
parent class:

https://github.com/openstack/nova/blob/8d9bf947a4c8654a30e016a5d95d9bec55447506/nova/virt/block_device.py#L516

I hope this helps. It only took me 4 years to memorize the flow. :)

-- 

Thanks,

Matt



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