On Wed, Sep 27, 2017 at 10:29 AM, Matt Riedemann email@example.com
On 9/23/2017 8:58 AM, LIU Yulong wrote:
Hi nova developers,
This mail is proposed to reconsider the key pair resetting of instance.
The nova queens PTG discuss is here: https://etherpad.openstack.org
/p/nova-ptg-queens https://etherpad.openstack.org/p/nova-ptg-queens L498.
And there are now two proposals.
SPEC 1: https://review.openstack.org/#/c/375221/ <
https://review.openstack.org/#/c/375221/ started by me (liuyulong)
since sep 2016.
This spec will allow setting the new key_name for the instance during
rebuild API. That’s a very simple and well-understood approach:
- Make consistent with rebuild API properties, such as name, imageRef,
metadata, adminPass etc.
- Rebuild API is something like
recreating, this is the right way to
do key pair updating. For keypair-login-only VM, this is the key
- This does not involve to other APIs like reboot/unshelve etc.
This was one of the issues I brought up in IRC, is that if we just
implemented this for the rebuild API, then someone could also ask that we
do it for things like reboot, cold migrate/resize, unshelve, etc. Anything
that involves re-creating the guest.
IMHO, rebuild has its own meaning is that we are going to recreate a VM.
So those inputs such as name, key, password should have a chance to be
reset in this
rebuild interface. Unlike reboot, cold migrate/resize,
unshelve, those actions does not have such potential implication. If
anything else involved, you are expanding those actions (reboot, cold
- Easy to use, only one API.
Until someone says we should also do it for the other APIs, as noted above.
This could not be acceptable. Other APIs does not have such
background. For rebuild, you are going to renew an instance, so those
params for instance creation should have chance to be reset.
It's been open because the spec was never approved. Just a procedural
- SPEC 2 : https://review.openstack.org/#/c/506552/ <
https://review.openstack.org/#/c/506552/ propose by Kevin_zheng.
This spec supposed to add a new updating API for one instance’s key pair.
This one has one foreseeable advantage for this is to do instance running
But it may cause some issues:
- This approach needs to update the instance key pair first (one step,
API call). And then do a reboot/rebuild or any actions causing the
vm restart (second step, another API call). Firstly, this is waste,
it use two API calls. Secondly, if updating key pair was done, and
the reboot was not. That may result an inconsistent between instance
DB key pair and guest VM inside key. Cloud user may confused to
choose which key should be used to login.
- I don't think multiple API calls is a problem. Any GUI or orchestration
tool can stitch these APIs together for what appears to be a single
operation for the end user. Furthermore, with multiple options about what
to do after the instance.key_name is updated, something like a GUI could
present the user with the option to picking if they want to reboot or
rebuild after the key is updated.
We provided a discontinuous API, so we should take responsibilities for
it. This inconsistent between instance DB key pair and guest VM inside can
stay there. So GUI or orchestration tool can not be a reasonable support.
More API calls may cause more problems. What if the GUI or orchestration
tool user/developer forget the second API? What if the first API failed,
should the retry all the APIs? Which key should be used to login if first
API succeed and the second not succeed/not response? What if the second API
failed? They confused again and again.
- An orchestrator or GUI would make sure that both APIs are called. For a
user that is updating the key_name, they should realize they need to make
another API call to enable it. This would all be in the API reference
documentation, CLI help, etc, that anyone doing this should read and
- For the second step (reboot), there is a strong constraint is that
> cloud-init config needs to be set to running-per-booting. But if a
> cloud platform all images are set cloud-init to per-deployment. In
> order to achieve this new API goal, the entire cloud platform images
> need updating. This will cause a huge upgrading work for entire
> cloud platform images. They need to change all the images cloud-init
> config from running-per-deployment to running-every-boot. But that
> still can not solve the inconsistent between DB keypair and
> guest-key. For instance, if the running VM is based on a
> running-once-cloud-init image: 1. create image from this VM; 2.
> change the keypair of the new VM; 3. reboot still can not work
> because of the old config of per-deployment-running.
This is per-cloud configuration, and as such it should be documented with
the cloud documentation. I can't say what is more "normal" for OpenStack
clouds to be doing with cloud-init here, that would be a good question for
the operators community (I've cross posted to the ops ML).
This upgrading issue could make a result that
rebuild become the only
way to apply new key to VM.
- For another second step (rebuild), if they have to rebuild, or
> rebuild is the only one way to deployment new key, we are going back
> to rebuild SPEC 1. Two steps for keypair updating are not good. Why
> don’t directly using SPEC 1?
Because of the points made above, which are if I can simply reboot my
instance to use the new keypair rather than rebuild it, that is much
better. Plus then it doesn't just limit us to rebuild, but the new key
could also be used after unshelving or cold migrating the instance.
This the point we are going to expand functionalities of
reboot/migrate/unshelving? Quoting the point you mentioned above "someone
may say we should also do it for the other APIs, like restart, evacuate,
start ? " What about password/name/image/flavor/user-data, one day these
can also be reset in reboot/migrate/unshelving/restart/evacuate/start API ?
- Another perspective to think about this is that SPEC 2 is expanding
> the functionality of reboot. What about one day user want to change
> password/name/personality at a reboot?
Kevin's spec does not propose any change to the reboot (or rebuild) APIs.
Yes, but if you change the key first, reboot may become the key step for
applying the key to VM. Reboot does not just reboot a VM, it takes a
new responsibility. For rebuild, SPEC 1 makes sense.
- Cloud user may still have questions: why key pair can not be updated
> during rebuilding ? Why name/image/personality can?
> * If new API does not supporting running injection, the DB keypair and
> guest keypair are inconsistent if cloud user forget a rebuiding,
> reboot, unshelving API call.
This is the same as the point made above, which I replied to, but anyone
calling the native APIs should be reading the docs and understanding what
they do. If they don't want that level of detail, use a GUI or
Discontinuous API results such concern. APIs are fixed, users are variable.
Thanks for at starting this discussion in the mailing list and summarizing
the concerns with both approaches.
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