Re: [openstack-dev] [glance] Option to skip deleting images in use?

2014-12-18 Thread Kuvaja, Erno
I think that's horrible idea. How do we do that store independent with the 
linking dependencies?

We should not depend universal use case like this on limited subset of 
backends, specially non-OpenStack ones. Glance (nor Nova) should never depend 
having direct access to the actual medium where the images are stored. I think 
this is school book example for something called database. Well arguable if 
this should be tracked at Glance or Nova, but definitely not a dirty hack 
expecting specific backend characteristics.

As mentioned before the protected image property is to ensure that the image 
does not get deleted, that is also easy to track when the images are queried. 
Perhaps the record needs to track the original state of protected flag, image 
id and use count. 3 column table and couple of API calls. Lets not at least 
make it any more complicated than it needs to be if such functionality is 
desired.


-  Erno

From: Nikhil Komawar [mailto:nikhil.koma...@rackspace.com]
Sent: 17 December 2014 20:34
To: OpenStack Development Mailing List (not for usage questions)
Subject: Re: [openstack-dev] [glance] Option to skip deleting images in use?

Guess that's a implementation detail. Depends on the way you go about using 
what's available now, I suppose.

Thanks,
-Nikhil

From: Chris St. Pierre [chris.a.st.pie...@gmail.com]
Sent: Wednesday, December 17, 2014 2:07 PM
To: OpenStack Development Mailing List (not for usage questions)
Subject: Re: [openstack-dev] [glance] Option to skip deleting images in use?
I was assuming atomic increment/decrement operations, in which case I'm not 
sure I see the race conditions. Or is atomism assuming too much?

On Wed, Dec 17, 2014 at 11:59 AM, Nikhil Komawar 
nikhil.koma...@rackspace.commailto:nikhil.koma...@rackspace.com wrote:
That looks like a decent alternative if it works. However, it would be too racy 
unless we we implement a test-and-set for such properties or there is a 
different job which queues up these requests and perform sequentially for each 
tenant.

Thanks,
-Nikhil

From: Chris St. Pierre 
[chris.a.st.pie...@gmail.commailto:chris.a.st.pie...@gmail.com]
Sent: Wednesday, December 17, 2014 10:23 AM
To: OpenStack Development Mailing List (not for usage questions)
Subject: Re: [openstack-dev] [glance] Option to skip deleting images in use?
That's unfortunately too simple. You run into one of two cases:

1. If the job automatically removes the protected attribute when an image is no 
longer in use, then you lose the ability to use protected on images that are 
not in use. I.e., there's no way to say, nothing is currently using this 
image, but please keep it around. (This seems particularly useful for 
snapshots, for instance.)

2. If the job does not automatically remove the protected attribute, then an 
image would be protected if it had ever been in use; to delete an image, you'd 
have to manually un-protect it, which is a workflow that quite explicitly 
defeats the whole purpose of flagging images as protected when they're in use.

It seems like flagging an image as *not* in use is actually a fairly difficult 
problem, since it requires consensus among all components that might be using 
images.

The only solution that readily occurs to me would be to add something like a 
filesystem link count to images in Glance. Then when Nova spawns an instance, 
it increments the usage count; when the instance is destroyed, the usage count 
is decremented. And similarly with other components that use images. An image 
could only be deleted when its usage count was zero.

There are ample opportunities to get out of sync there, but it's at least a 
sketch of something that might work, and isn't *too* horribly hackish. Thoughts?

On Tue, Dec 16, 2014 at 6:11 PM, Vishvananda Ishaya 
vishvana...@gmail.commailto:vishvana...@gmail.com wrote:
A simple solution that wouldn't require modification of glance would be a cron 
job
that lists images and snapshots and marks them protected while they are in use.

Vish

On Dec 16, 2014, at 3:19 PM, Collins, Sean 
sean_colli...@cable.comcast.commailto:sean_colli...@cable.comcast.com wrote:

 On Tue, Dec 16, 2014 at 05:12:31PM EST, Chris St. Pierre wrote:
 No, I'm looking to prevent images that are in use from being deleted. In
 use and protected are disjoint sets.

 I have seen multiple cases of images (and snapshots) being deleted while
 still in use in Nova, which leads to some very, shall we say,
 interesting bugs and support problems.

 I do think that we should try and determine a way forward on this, they
 are indeed disjoint sets. Setting an image as protected is a proactive
 measure, we should try and figure out a way to keep tenants from
 shooting themselves in the foot if possible.

 --
 Sean M. Collins
 ___
 OpenStack-dev mailing list
 OpenStack-dev@lists.openstack.orgmailto:OpenStack-dev@lists.openstack.org

Re: [openstack-dev] [glance] Option to skip deleting images in use?

2014-12-18 Thread Chris St. Pierre
I wasn't suggesting that we *actually* use filesystem link count, and make
hard links or whatever for every time the image is used. That's prima facie
absurd, for a lot more reasons that you point out. I was suggesting a new
database field that tracks the number of times an image is in use, by
*analogy* with filesystem link counts. (If I wanted to be unnecessarily
abrasive I might say, This is a textbook example of something called an
analogy, but I'm not interested in being unnecessarily abrasive.)

Overloading the protected flag is *still* a terrible hack. Even if we
tracked the initial state of protected and restored that state when an
image went out of use, that would negate the ability to make an image
protected while it was in use and expect that change to remain in place. So
that just violates the principle of least surprise. Of course, we could
have glance modify the original_protected_state flag when that flag is
non-null and the user changes the actual protected flag, but this is just
layering hacks upon hacks. By actually tracking the number of times an
image is in use, we can preserve the ability to protect images *and* avoid
deleting images in use.

On Thu, Dec 18, 2014 at 5:27 AM, Kuvaja, Erno kuv...@hp.com wrote:

  I think that’s horrible idea. How do we do that store independent with
 the linking dependencies?



 We should not depend universal use case like this on limited subset of
 backends, specially non-OpenStack ones. Glance (nor Nova) should never
 depend having direct access to the actual medium where the images are
 stored. I think this is school book example for something called database.
 Well arguable if this should be tracked at Glance or Nova, but definitely
 not a dirty hack expecting specific backend characteristics.



 As mentioned before the protected image property is to ensure that the
 image does not get deleted, that is also easy to track when the images are
 queried. Perhaps the record needs to track the original state of protected
 flag, image id and use count. 3 column table and couple of API calls. Lets
 not at least make it any more complicated than it needs to be if such
 functionality is desired.



 -  Erno



 *From:* Nikhil Komawar [mailto:nikhil.koma...@rackspace.com]
 *Sent:* 17 December 2014 20:34

 *To:* OpenStack Development Mailing List (not for usage questions)
 *Subject:* Re: [openstack-dev] [glance] Option to skip deleting images in
 use?



 Guess that's a implementation detail. Depends on the way you go about
 using what's available now, I suppose.



 Thanks,
 -Nikhil
   --

 *From:* Chris St. Pierre [chris.a.st.pie...@gmail.com]
 *Sent:* Wednesday, December 17, 2014 2:07 PM
 *To:* OpenStack Development Mailing List (not for usage questions)
 *Subject:* Re: [openstack-dev] [glance] Option to skip deleting images in
 use?

 I was assuming atomic increment/decrement operations, in which case I'm
 not sure I see the race conditions. Or is atomism assuming too much?



 On Wed, Dec 17, 2014 at 11:59 AM, Nikhil Komawar 
 nikhil.koma...@rackspace.com wrote:

  That looks like a decent alternative if it works. However, it would be
 too racy unless we we implement a test-and-set for such properties or there
 is a different job which queues up these requests and perform sequentially
 for each tenant.



 Thanks,
 -Nikhil
   --

 *From:* Chris St. Pierre [chris.a.st.pie...@gmail.com]
 *Sent:* Wednesday, December 17, 2014 10:23 AM
 *To:* OpenStack Development Mailing List (not for usage questions)
 *Subject:* Re: [openstack-dev] [glance] Option to skip deleting images in
 use?

 That's unfortunately too simple. You run into one of two cases:



 1. If the job automatically removes the protected attribute when an image
 is no longer in use, then you lose the ability to use protected on images
 that are not in use. I.e., there's no way to say, nothing is currently
 using this image, but please keep it around. (This seems particularly
 useful for snapshots, for instance.)



 2. If the job does not automatically remove the protected attribute, then
 an image would be protected if it had ever been in use; to delete an image,
 you'd have to manually un-protect it, which is a workflow that quite
 explicitly defeats the whole purpose of flagging images as protected when
 they're in use.



 It seems like flagging an image as *not* in use is actually a fairly
 difficult problem, since it requires consensus among all components that
 might be using images.



 The only solution that readily occurs to me would be to add something like
 a filesystem link count to images in Glance. Then when Nova spawns an
 instance, it increments the usage count; when the instance is destroyed,
 the usage count is decremented. And similarly with other components that
 use images. An image could only be deleted when its usage count was zero.



 There are ample opportunities to get out of sync there, but it's at least

Re: [openstack-dev] [glance] Option to skip deleting images in use?

2014-12-18 Thread Jay Pipes

On 12/18/2014 02:08 PM, Chris St. Pierre wrote:

I wasn't suggesting that we *actually* use filesystem link count, and
make hard links or whatever for every time the image is used. That's
prima facie absurd, for a lot more reasons that you point out. I was
suggesting a new database field that tracks the number of times an image
is in use, by *analogy* with filesystem link counts. (If I wanted to be
unnecessarily abrasive I might say, This is a textbook example of
something called an analogy, but I'm not interested in being
unnecessarily abrasive.)

Overloading the protected flag is *still* a terrible hack. Even if we
tracked the initial state of protected and restored that state when an
image went out of use, that would negate the ability to make an image


I guess I don't understand what you consider to be overloading of the 
protected flag. The original purpose of the protected flag was to 
protect images from being deleted.


Best,
-jay


protected while it was in use and expect that change to remain in place.
So that just violates the principle of least surprise. Of course, we
could have glance modify the original_protected_state flag when that
flag is non-null and the user changes the actual protected flag, but
this is just layering hacks upon hacks. By actually tracking the number
of times an image is in use, we can preserve the ability to protect
images *and* avoid deleting images in use.

On Thu, Dec 18, 2014 at 5:27 AM, Kuvaja, Erno kuv...@hp.com
mailto:kuv...@hp.com wrote:

I think that’s horrible idea. How do we do that store independent
with the linking dependencies?

__ __

We should not depend universal use case like this on limited subset
of backends, specially non-OpenStack ones. Glance (nor Nova) should
never depend having direct access to the actual medium where the
images are stored. I think this is school book example for something
called database. Well arguable if this should be tracked at Glance
or Nova, but definitely not a dirty hack expecting specific backend
characteristics.

__ __

As mentioned before the protected image property is to ensure that
the image does not get deleted, that is also easy to track when the
images are queried. Perhaps the record needs to track the original
state of protected flag, image id and use count. 3 column table and
couple of API calls. Lets not at least make it any more complicated
than it needs to be if such functionality is desired.

__ __

__-__Erno

__ __

*From:*Nikhil Komawar [mailto:nikhil.koma...@rackspace.com
mailto:nikhil.koma...@rackspace.com]
*Sent:* 17 December 2014 20:34


*To:* OpenStack Development Mailing List (not for usage questions)
*Subject:* Re: [openstack-dev] [glance] Option to skip deleting
images in use?

__ __

Guess that's a implementation detail. Depends on the way you go
about using what's available now, I suppose.

__ __

Thanks,
-Nikhil



*From:*Chris St. Pierre [chris.a.st.pie...@gmail.com
mailto:chris.a.st.pie...@gmail.com]
*Sent:* Wednesday, December 17, 2014 2:07 PM
*To:* OpenStack Development Mailing List (not for usage questions)
*Subject:* Re: [openstack-dev] [glance] Option to skip deleting
images in use?

I was assuming atomic increment/decrement operations, in which case
I'm not sure I see the race conditions. Or is atomism assuming too
much?

__ __

On Wed, Dec 17, 2014 at 11:59 AM, Nikhil Komawar
nikhil.koma...@rackspace.com mailto:nikhil.koma...@rackspace.com
wrote:

That looks like a decent alternative if it works. However, it
would be too racy unless we we implement a test-and-set for such
properties or there is a different job which queues up these
requests and perform sequentially for each tenant.

__ __

Thanks,
-Nikhil



*From:*Chris St. Pierre [chris.a.st.pie...@gmail.com
mailto:chris.a.st.pie...@gmail.com]
*Sent:* Wednesday, December 17, 2014 10:23 AM
*To:* OpenStack Development Mailing List (not for usage questions)
*Subject:* Re: [openstack-dev] [glance] Option to skip deleting
images in use?

That's unfortunately too simple. You run into one of two cases: 

__ __

1. If the job automatically removes the protected attribute when
an image is no longer in use, then you lose the ability to use
protected on images that are not in use. I.e., there's no way
to say, nothing is currently using this image, but please keep
it around. (This seems particularly useful for snapshots, for
instance.)

__ __

2. If the job does

Re: [openstack-dev] [glance] Option to skip deleting images in use?

2014-12-18 Thread Chris St. Pierre
Presumably to prevent images from being deleted for arbitrary reasons that
are left to the administrator(s) of each individual implementation of
OpenStack, though. Using the protected flag to prevent images that are in
use from being deleted obviates the ability to use it for arbitrary
protection. That is, it can either be used as a general purpose flag to
prevent deletion of an image; or it can be used as a flag for images that
are in use and thus must not be deleted; but it cannot be used for both.
(At least, not without a wild and woolly network of hacks to ensure that it
can serve both purposes.)

Given the general-purpose nature of the flag, I don't think that something
that should be taken away from the administrators. And yet, it's very
desirable to prevent deletion of images that are in use. I think both of
these things should be supported, at the same time on the same
installation. I do not consider it a solution to the problem that images
can be deleted in use to take the protected flag away from arbitrary,
bespoke use.

On Thu, Dec 18, 2014 at 6:44 PM, Jay Pipes jaypi...@gmail.com wrote:

 On 12/18/2014 02:08 PM, Chris St. Pierre wrote:

 I wasn't suggesting that we *actually* use filesystem link count, and
 make hard links or whatever for every time the image is used. That's
 prima facie absurd, for a lot more reasons that you point out. I was
 suggesting a new database field that tracks the number of times an image
 is in use, by *analogy* with filesystem link counts. (If I wanted to be
 unnecessarily abrasive I might say, This is a textbook example of
 something called an analogy, but I'm not interested in being
 unnecessarily abrasive.)

 Overloading the protected flag is *still* a terrible hack. Even if we
 tracked the initial state of protected and restored that state when an
 image went out of use, that would negate the ability to make an image


 I guess I don't understand what you consider to be overloading of the
 protected flag. The original purpose of the protected flag was to protect
 images from being deleted.

 Best,
 -jay

  protected while it was in use and expect that change to remain in place.
 So that just violates the principle of least surprise. Of course, we
 could have glance modify the original_protected_state flag when that
 flag is non-null and the user changes the actual protected flag, but
 this is just layering hacks upon hacks. By actually tracking the number
 of times an image is in use, we can preserve the ability to protect
 images *and* avoid deleting images in use.

 On Thu, Dec 18, 2014 at 5:27 AM, Kuvaja, Erno kuv...@hp.com
 mailto:kuv...@hp.com wrote:

 I think that’s horrible idea. How do we do that store independent
 with the linking dependencies?

 __ __

 We should not depend universal use case like this on limited subset
 of backends, specially non-OpenStack ones. Glance (nor Nova) should
 never depend having direct access to the actual medium where the
 images are stored. I think this is school book example for something
 called database. Well arguable if this should be tracked at Glance
 or Nova, but definitely not a dirty hack expecting specific backend
 characteristics.

 __ __

 As mentioned before the protected image property is to ensure that
 the image does not get deleted, that is also easy to track when the
 images are queried. Perhaps the record needs to track the original
 state of protected flag, image id and use count. 3 column table and
 couple of API calls. Lets not at least make it any more complicated
 than it needs to be if such functionality is desired.

 __ __

 __-__Erno

 __ __

 *From:*Nikhil Komawar [mailto:nikhil.koma...@rackspace.com
 mailto:nikhil.koma...@rackspace.com]
 *Sent:* 17 December 2014 20:34


 *To:* OpenStack Development Mailing List (not for usage questions)
 *Subject:* Re: [openstack-dev] [glance] Option to skip deleting
 images in use?

 __ __

 Guess that's a implementation detail. Depends on the way you go
 about using what's available now, I suppose.

 __ __

 Thanks,
 -Nikhil

 
 

 *From:*Chris St. Pierre [chris.a.st.pie...@gmail.com
 mailto:chris.a.st.pie...@gmail.com]
 *Sent:* Wednesday, December 17, 2014 2:07 PM
 *To:* OpenStack Development Mailing List (not for usage questions)
 *Subject:* Re: [openstack-dev] [glance] Option to skip deleting
 images in use?

 I was assuming atomic increment/decrement operations, in which case
 I'm not sure I see the race conditions. Or is atomism assuming too
 much?

 __ __

 On Wed, Dec 17, 2014 at 11:59 AM, Nikhil Komawar
 nikhil.koma...@rackspace.com mailto:nikhil.koma...@rackspace.com
 wrote:

 That looks like a decent alternative if it works. However

Re: [openstack-dev] [glance] Option to skip deleting images in use?

2014-12-17 Thread Chris St. Pierre
That's unfortunately too simple. You run into one of two cases:

1. If the job automatically removes the protected attribute when an image
is no longer in use, then you lose the ability to use protected on images
that are not in use. I.e., there's no way to say, nothing is currently
using this image, but please keep it around. (This seems particularly
useful for snapshots, for instance.)

2. If the job does not automatically remove the protected attribute, then
an image would be protected if it had ever been in use; to delete an image,
you'd have to manually un-protect it, which is a workflow that quite
explicitly defeats the whole purpose of flagging images as protected when
they're in use.

It seems like flagging an image as *not* in use is actually a fairly
difficult problem, since it requires consensus among all components that
might be using images.

The only solution that readily occurs to me would be to add something like
a filesystem link count to images in Glance. Then when Nova spawns an
instance, it increments the usage count; when the instance is destroyed,
the usage count is decremented. And similarly with other components that
use images. An image could only be deleted when its usage count was zero.

There are ample opportunities to get out of sync there, but it's at least a
sketch of something that might work, and isn't *too* horribly hackish.
Thoughts?

On Tue, Dec 16, 2014 at 6:11 PM, Vishvananda Ishaya vishvana...@gmail.com
wrote:

 A simple solution that wouldn’t require modification of glance would be a
 cron job
 that lists images and snapshots and marks them protected while they are in
 use.

 Vish

 On Dec 16, 2014, at 3:19 PM, Collins, Sean 
 sean_colli...@cable.comcast.com wrote:

  On Tue, Dec 16, 2014 at 05:12:31PM EST, Chris St. Pierre wrote:
  No, I'm looking to prevent images that are in use from being deleted.
 In
  use and protected are disjoint sets.
 
  I have seen multiple cases of images (and snapshots) being deleted while
  still in use in Nova, which leads to some very, shall we say,
  interesting bugs and support problems.
 
  I do think that we should try and determine a way forward on this, they
  are indeed disjoint sets. Setting an image as protected is a proactive
  measure, we should try and figure out a way to keep tenants from
  shooting themselves in the foot if possible.
 
  --
  Sean M. Collins
  ___
  OpenStack-dev mailing list
  OpenStack-dev@lists.openstack.org
  http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev


 ___
 OpenStack-dev mailing list
 OpenStack-dev@lists.openstack.org
 http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev




-- 
Chris St. Pierre
___
OpenStack-dev mailing list
OpenStack-dev@lists.openstack.org
http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev


Re: [openstack-dev] [glance] Option to skip deleting images in use?

2014-12-17 Thread Nikhil Komawar
That looks like a decent alternative if it works. However, it would be too racy 
unless we we implement a test-and-set for such properties or there is a 
different job which queues up these requests and perform sequentially for each 
tenant.

Thanks,
-Nikhil

From: Chris St. Pierre [chris.a.st.pie...@gmail.com]
Sent: Wednesday, December 17, 2014 10:23 AM
To: OpenStack Development Mailing List (not for usage questions)
Subject: Re: [openstack-dev] [glance] Option to skip deleting images in use?

That's unfortunately too simple. You run into one of two cases:

1. If the job automatically removes the protected attribute when an image is no 
longer in use, then you lose the ability to use protected on images that are 
not in use. I.e., there's no way to say, nothing is currently using this 
image, but please keep it around. (This seems particularly useful for 
snapshots, for instance.)

2. If the job does not automatically remove the protected attribute, then an 
image would be protected if it had ever been in use; to delete an image, you'd 
have to manually un-protect it, which is a workflow that quite explicitly 
defeats the whole purpose of flagging images as protected when they're in use.

It seems like flagging an image as *not* in use is actually a fairly difficult 
problem, since it requires consensus among all components that might be using 
images.

The only solution that readily occurs to me would be to add something like a 
filesystem link count to images in Glance. Then when Nova spawns an instance, 
it increments the usage count; when the instance is destroyed, the usage count 
is decremented. And similarly with other components that use images. An image 
could only be deleted when its usage count was zero.

There are ample opportunities to get out of sync there, but it's at least a 
sketch of something that might work, and isn't *too* horribly hackish. Thoughts?

On Tue, Dec 16, 2014 at 6:11 PM, Vishvananda Ishaya 
vishvana...@gmail.commailto:vishvana...@gmail.com wrote:
A simple solution that wouldn’t require modification of glance would be a cron 
job
that lists images and snapshots and marks them protected while they are in use.

Vish

On Dec 16, 2014, at 3:19 PM, Collins, Sean 
sean_colli...@cable.comcast.commailto:sean_colli...@cable.comcast.com wrote:

 On Tue, Dec 16, 2014 at 05:12:31PM EST, Chris St. Pierre wrote:
 No, I'm looking to prevent images that are in use from being deleted. In
 use and protected are disjoint sets.

 I have seen multiple cases of images (and snapshots) being deleted while
 still in use in Nova, which leads to some very, shall we say,
 interesting bugs and support problems.

 I do think that we should try and determine a way forward on this, they
 are indeed disjoint sets. Setting an image as protected is a proactive
 measure, we should try and figure out a way to keep tenants from
 shooting themselves in the foot if possible.

 --
 Sean M. Collins
 ___
 OpenStack-dev mailing list
 OpenStack-dev@lists.openstack.orgmailto:OpenStack-dev@lists.openstack.org
 http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev


___
OpenStack-dev mailing list
OpenStack-dev@lists.openstack.orgmailto:OpenStack-dev@lists.openstack.org
http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev



--
Chris St. Pierre
___
OpenStack-dev mailing list
OpenStack-dev@lists.openstack.org
http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev


Re: [openstack-dev] [glance] Option to skip deleting images in use?

2014-12-17 Thread Chris St. Pierre
I was assuming atomic increment/decrement operations, in which case I'm not
sure I see the race conditions. Or is atomism assuming too much?

On Wed, Dec 17, 2014 at 11:59 AM, Nikhil Komawar 
nikhil.koma...@rackspace.com wrote:

  That looks like a decent alternative if it works. However, it would be
 too racy unless we we implement a test-and-set for such properties or there
 is a different job which queues up these requests and perform sequentially
 for each tenant.

 Thanks,
 -Nikhil
   --
 *From:* Chris St. Pierre [chris.a.st.pie...@gmail.com]
 *Sent:* Wednesday, December 17, 2014 10:23 AM
 *To:* OpenStack Development Mailing List (not for usage questions)
 *Subject:* Re: [openstack-dev] [glance] Option to skip deleting images in
 use?

   That's unfortunately too simple. You run into one of two cases:

  1. If the job automatically removes the protected attribute when an
 image is no longer in use, then you lose the ability to use protected on
 images that are not in use. I.e., there's no way to say, nothing is
 currently using this image, but please keep it around. (This seems
 particularly useful for snapshots, for instance.)

  2. If the job does not automatically remove the protected attribute,
 then an image would be protected if it had ever been in use; to delete an
 image, you'd have to manually un-protect it, which is a workflow that quite
 explicitly defeats the whole purpose of flagging images as protected when
 they're in use.

  It seems like flagging an image as *not* in use is actually a fairly
 difficult problem, since it requires consensus among all components that
 might be using images.

  The only solution that readily occurs to me would be to add something
 like a filesystem link count to images in Glance. Then when Nova spawns an
 instance, it increments the usage count; when the instance is destroyed,
 the usage count is decremented. And similarly with other components that
 use images. An image could only be deleted when its usage count was zero.

  There are ample opportunities to get out of sync there, but it's at
 least a sketch of something that might work, and isn't *too* horribly
 hackish. Thoughts?

 On Tue, Dec 16, 2014 at 6:11 PM, Vishvananda Ishaya vishvana...@gmail.com
  wrote:

 A simple solution that wouldn’t require modification of glance would be a
 cron job
 that lists images and snapshots and marks them protected while they are
 in use.

 Vish

 On Dec 16, 2014, at 3:19 PM, Collins, Sean 
 sean_colli...@cable.comcast.com wrote:

  On Tue, Dec 16, 2014 at 05:12:31PM EST, Chris St. Pierre wrote:
  No, I'm looking to prevent images that are in use from being deleted.
 In
  use and protected are disjoint sets.
 
  I have seen multiple cases of images (and snapshots) being deleted while
  still in use in Nova, which leads to some very, shall we say,
  interesting bugs and support problems.
 
  I do think that we should try and determine a way forward on this, they
  are indeed disjoint sets. Setting an image as protected is a proactive
  measure, we should try and figure out a way to keep tenants from
  shooting themselves in the foot if possible.
 
  --
  Sean M. Collins
  ___
  OpenStack-dev mailing list
  OpenStack-dev@lists.openstack.org
  http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev


 ___
 OpenStack-dev mailing list
 OpenStack-dev@lists.openstack.org
 http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev




  --
 Chris St. Pierre

 ___
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Re: [openstack-dev] [glance] Option to skip deleting images in use?

2014-12-17 Thread Nikhil Komawar
Guess that's a implementation detail. Depends on the way you go about using 
what's available now, I suppose.

Thanks,
-Nikhil

From: Chris St. Pierre [chris.a.st.pie...@gmail.com]
Sent: Wednesday, December 17, 2014 2:07 PM
To: OpenStack Development Mailing List (not for usage questions)
Subject: Re: [openstack-dev] [glance] Option to skip deleting images in use?

I was assuming atomic increment/decrement operations, in which case I'm not 
sure I see the race conditions. Or is atomism assuming too much?

On Wed, Dec 17, 2014 at 11:59 AM, Nikhil Komawar 
nikhil.koma...@rackspace.commailto:nikhil.koma...@rackspace.com wrote:
That looks like a decent alternative if it works. However, it would be too racy 
unless we we implement a test-and-set for such properties or there is a 
different job which queues up these requests and perform sequentially for each 
tenant.

Thanks,
-Nikhil

From: Chris St. Pierre 
[chris.a.st.pie...@gmail.commailto:chris.a.st.pie...@gmail.com]
Sent: Wednesday, December 17, 2014 10:23 AM
To: OpenStack Development Mailing List (not for usage questions)
Subject: Re: [openstack-dev] [glance] Option to skip deleting images in use?

That's unfortunately too simple. You run into one of two cases:

1. If the job automatically removes the protected attribute when an image is no 
longer in use, then you lose the ability to use protected on images that are 
not in use. I.e., there's no way to say, nothing is currently using this 
image, but please keep it around. (This seems particularly useful for 
snapshots, for instance.)

2. If the job does not automatically remove the protected attribute, then an 
image would be protected if it had ever been in use; to delete an image, you'd 
have to manually un-protect it, which is a workflow that quite explicitly 
defeats the whole purpose of flagging images as protected when they're in use.

It seems like flagging an image as *not* in use is actually a fairly difficult 
problem, since it requires consensus among all components that might be using 
images.

The only solution that readily occurs to me would be to add something like a 
filesystem link count to images in Glance. Then when Nova spawns an instance, 
it increments the usage count; when the instance is destroyed, the usage count 
is decremented. And similarly with other components that use images. An image 
could only be deleted when its usage count was zero.

There are ample opportunities to get out of sync there, but it's at least a 
sketch of something that might work, and isn't *too* horribly hackish. Thoughts?

On Tue, Dec 16, 2014 at 6:11 PM, Vishvananda Ishaya 
vishvana...@gmail.commailto:vishvana...@gmail.com wrote:
A simple solution that wouldn’t require modification of glance would be a cron 
job
that lists images and snapshots and marks them protected while they are in use.

Vish

On Dec 16, 2014, at 3:19 PM, Collins, Sean 
sean_colli...@cable.comcast.commailto:sean_colli...@cable.comcast.com wrote:

 On Tue, Dec 16, 2014 at 05:12:31PM EST, Chris St. Pierre wrote:
 No, I'm looking to prevent images that are in use from being deleted. In
 use and protected are disjoint sets.

 I have seen multiple cases of images (and snapshots) being deleted while
 still in use in Nova, which leads to some very, shall we say,
 interesting bugs and support problems.

 I do think that we should try and determine a way forward on this, they
 are indeed disjoint sets. Setting an image as protected is a proactive
 measure, we should try and figure out a way to keep tenants from
 shooting themselves in the foot if possible.

 --
 Sean M. Collins
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Re: [openstack-dev] [glance] Option to skip deleting images in use?

2014-12-16 Thread Jay Pipes
Just set the images to is_public=False as an admin and they'll disappear 
from everyone except the admin.


-jay

On 12/16/2014 03:09 PM, Chris St. Pierre wrote:

Currently, with delay_delete enabled, the Glance scrubber happily
deletes whatever images you ask it to. That includes images that are
currently in use by Nova guests, which can really hose things. It'd be
nice to have an option to tell the scrubber to skip deletion of images
that are currently in use, which is fairly trivial to check for and
provides a nice measure of protection.

Without delay_delete enabled, checking for images in use likely takes
too much time, so this would be limited to just images that are scrubbed
with delay_delete.

I wanted to bring this up here before I go to the trouble of writing a
spec for it, particularly since it doesn't appear that glance currently
talks to Nova as a client at all. Is this something that folks would be
interested in having? Thanks!

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Re: [openstack-dev] [glance] Option to skip deleting images in use?

2014-12-16 Thread Chris St. Pierre
The goal here is protection against deletion of in-use images, not a
workaround that can be executed by an admin. For instance, someone without
admin still can't do that, and someone with a fat finger can still delete
images in use.

Don't lose your data is a fine workaround for taking backups, but most of
us take backups anyway. Same deal.

On Tue, Dec 16, 2014 at 2:30 PM, Jay Pipes jaypi...@gmail.com wrote:

 Just set the images to is_public=False as an admin and they'll disappear
 from everyone except the admin.

 -jay


 On 12/16/2014 03:09 PM, Chris St. Pierre wrote:

 Currently, with delay_delete enabled, the Glance scrubber happily
 deletes whatever images you ask it to. That includes images that are
 currently in use by Nova guests, which can really hose things. It'd be
 nice to have an option to tell the scrubber to skip deletion of images
 that are currently in use, which is fairly trivial to check for and
 provides a nice measure of protection.

 Without delay_delete enabled, checking for images in use likely takes
 too much time, so this would be limited to just images that are scrubbed
 with delay_delete.

 I wanted to bring this up here before I go to the trouble of writing a
 spec for it, particularly since it doesn't appear that glance currently
 talks to Nova as a client at all. Is this something that folks would be
 interested in having? Thanks!

 --
 Chris St. Pierre


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Re: [openstack-dev] [glance] Option to skip deleting images in use?

2014-12-16 Thread Jay Pipes

On 12/16/2014 04:23 PM, Chris St. Pierre wrote:

The goal here is protection against deletion of in-use images, not a
workaround that can be executed by an admin. For instance, someone
without admin still can't do that, and someone with a fat finger can
still delete images in use.


Then set the protected property on the image, which prevents it from 
being deleted.


From the glance CLI image-update help output:

--is-protected [True|False]
Prevent image from being deleted.


Don't lose your data is a fine workaround for taking backups, but most
of us take backups anyway. Same deal.

On Tue, Dec 16, 2014 at 2:30 PM, Jay Pipes jaypi...@gmail.com
mailto:jaypi...@gmail.com wrote:

Just set the images to is_public=False as an admin and they'll
disappear from everyone except the admin.

-jay


On 12/16/2014 03:09 PM, Chris St. Pierre wrote:

Currently, with delay_delete enabled, the Glance scrubber happily
deletes whatever images you ask it to. That includes images that are
currently in use by Nova guests, which can really hose things.
It'd be
nice to have an option to tell the scrubber to skip deletion of
images
that are currently in use, which is fairly trivial to check for and
provides a nice measure of protection.

Without delay_delete enabled, checking for images in use likely
takes
too much time, so this would be limited to just images that are
scrubbed
with delay_delete.

I wanted to bring this up here before I go to the trouble of
writing a
spec for it, particularly since it doesn't appear that glance
currently
talks to Nova as a client at all. Is this something that folks
would be
interested in having? Thanks!

--
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Re: [openstack-dev] [glance] Option to skip deleting images in use?

2014-12-16 Thread Nikhil Komawar
+1

Thanks,
-Nikhil


From: Jay Pipes [jaypi...@gmail.com]
Sent: Tuesday, December 16, 2014 4:33 PM
To: openstack-dev@lists.openstack.org
Subject: Re: [openstack-dev] [glance] Option to skip deleting images in use?

On 12/16/2014 04:23 PM, Chris St. Pierre wrote:
 The goal here is protection against deletion of in-use images, not a
 workaround that can be executed by an admin. For instance, someone
 without admin still can't do that, and someone with a fat finger can
 still delete images in use.

Then set the protected property on the image, which prevents it from
being deleted.

 From the glance CLI image-update help output:

--is-protected [True|False]
 Prevent image from being deleted.

 Don't lose your data is a fine workaround for taking backups, but most
 of us take backups anyway. Same deal.

 On Tue, Dec 16, 2014 at 2:30 PM, Jay Pipes jaypi...@gmail.com
 mailto:jaypi...@gmail.com wrote:

 Just set the images to is_public=False as an admin and they'll
 disappear from everyone except the admin.

 -jay


 On 12/16/2014 03:09 PM, Chris St. Pierre wrote:

 Currently, with delay_delete enabled, the Glance scrubber happily
 deletes whatever images you ask it to. That includes images that are
 currently in use by Nova guests, which can really hose things.
 It'd be
 nice to have an option to tell the scrubber to skip deletion of
 images
 that are currently in use, which is fairly trivial to check for and
 provides a nice measure of protection.

 Without delay_delete enabled, checking for images in use likely
 takes
 too much time, so this would be limited to just images that are
 scrubbed
 with delay_delete.

 I wanted to bring this up here before I go to the trouble of
 writing a
 spec for it, particularly since it doesn't appear that glance
 currently
 talks to Nova as a client at all. Is this something that folks
 would be
 interested in having? Thanks!

 --
 Chris St. Pierre


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Re: [openstack-dev] [glance] Option to skip deleting images in use?

2014-12-16 Thread Fei Long Wang

Hi Chris,

Are you looking for the 'protected' attribute? You can mark an image 
with 'protected'=True, then the image can't be deleted by accidentally.


On 17/12/14 10:23, Chris St. Pierre wrote:
The goal here is protection against deletion of in-use images, not a 
workaround that can be executed by an admin. For instance, someone 
without admin still can't do that, and someone with a fat finger can 
still delete images in use.


Don't lose your data is a fine workaround for taking backups, but 
most of us take backups anyway. Same deal.


On Tue, Dec 16, 2014 at 2:30 PM, Jay Pipes jaypi...@gmail.com 
mailto:jaypi...@gmail.com wrote:


Just set the images to is_public=False as an admin and they'll
disappear from everyone except the admin.

-jay


On 12/16/2014 03:09 PM, Chris St. Pierre wrote:

Currently, with delay_delete enabled, the Glance scrubber happily
deletes whatever images you ask it to. That includes images
that are
currently in use by Nova guests, which can really hose things.
It'd be
nice to have an option to tell the scrubber to skip deletion
of images
that are currently in use, which is fairly trivial to check
for and
provides a nice measure of protection.

Without delay_delete enabled, checking for images in use
likely takes
too much time, so this would be limited to just images that
are scrubbed
with delay_delete.

I wanted to bring this up here before I go to the trouble of
writing a
spec for it, particularly since it doesn't appear that glance
currently
talks to Nova as a client at all. Is this something that folks
would be
interested in having? Thanks!

--
Chris St. Pierre


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Re: [openstack-dev] [glance] Option to skip deleting images in use?

2014-12-16 Thread Chris St. Pierre
No, I'm looking to prevent images that are in use from being deleted. In
use and protected are disjoint sets.

On Tue, Dec 16, 2014 at 3:36 PM, Fei Long Wang feil...@catalyst.net.nz
wrote:

  Hi Chris,

 Are you looking for the 'protected' attribute? You can mark an image with
 'protected'=True, then the image can't be deleted by accidentally.

 On 17/12/14 10:23, Chris St. Pierre wrote:

 The goal here is protection against deletion of in-use images, not a
 workaround that can be executed by an admin. For instance, someone without
 admin still can't do that, and someone with a fat finger can still delete
 images in use.

  Don't lose your data is a fine workaround for taking backups, but most
 of us take backups anyway. Same deal.

 On Tue, Dec 16, 2014 at 2:30 PM, Jay Pipes jaypi...@gmail.com wrote:

 Just set the images to is_public=False as an admin and they'll disappear
 from everyone except the admin.

 -jay


 On 12/16/2014 03:09 PM, Chris St. Pierre wrote:

  Currently, with delay_delete enabled, the Glance scrubber happily
 deletes whatever images you ask it to. That includes images that are
 currently in use by Nova guests, which can really hose things. It'd be
 nice to have an option to tell the scrubber to skip deletion of images
 that are currently in use, which is fairly trivial to check for and
 provides a nice measure of protection.

 Without delay_delete enabled, checking for images in use likely takes
 too much time, so this would be limited to just images that are scrubbed
 with delay_delete.

 I wanted to bring this up here before I go to the trouble of writing a
 spec for it, particularly since it doesn't appear that glance currently
 talks to Nova as a client at all. Is this something that folks would be
 interested in having? Thanks!

 --
 Chris St. Pierre


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 --
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 Tel: +64-48032246
 Email: flw...@catalyst.net.nz
 Catalyst IT Limited
 Level 6, Catalyst House, 150 Willis Street, Wellington
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Re: [openstack-dev] [glance] Option to skip deleting images in use?

2014-12-16 Thread Nikhil Komawar
Hi Chris,

Apologies for not having heard your use case completely. From the description 
as well as the information you've provided; it is my recommendation to use a 
protected property in Glance for the Image entity that is in use. You can then 
use it in the service of your choice (Nova, Cinder) for not deleting the same. 
It is that service which shall have more accurate information as well as be 
source of truth for the in-use state of the Image entity. Making a call out to 
different service (except backend stores) is out of the scope of Glance. (Nova 
is the client of Glance and we would like to avoid the circular dependency mess 
there!)

Hope it helps. Please let me know if you need more information.

Thanks and Regards,
-Nikhil

From: Chris St. Pierre [chris.a.st.pie...@gmail.com]
Sent: Tuesday, December 16, 2014 5:12 PM
To: OpenStack Development Mailing List (not for usage questions)
Subject: Re: [openstack-dev] [glance] Option to skip deleting images in use?

No, I'm looking to prevent images that are in use from being deleted. In use 
and protected are disjoint sets.

On Tue, Dec 16, 2014 at 3:36 PM, Fei Long Wang 
feil...@catalyst.net.nzmailto:feil...@catalyst.net.nz wrote:
Hi Chris,

Are you looking for the 'protected' attribute? You can mark an image with 
'protected'=True, then the image can't be deleted by accidentally.

On 17/12/14 10:23, Chris St. Pierre wrote:
The goal here is protection against deletion of in-use images, not a workaround 
that can be executed by an admin. For instance, someone without admin still 
can't do that, and someone with a fat finger can still delete images in use.

Don't lose your data is a fine workaround for taking backups, but most of us 
take backups anyway. Same deal.

On Tue, Dec 16, 2014 at 2:30 PM, Jay Pipes 
jaypi...@gmail.commailto:jaypi...@gmail.com wrote:
Just set the images to is_public=False as an admin and they'll disappear from 
everyone except the admin.

-jay


On 12/16/2014 03:09 PM, Chris St. Pierre wrote:
Currently, with delay_delete enabled, the Glance scrubber happily
deletes whatever images you ask it to. That includes images that are
currently in use by Nova guests, which can really hose things. It'd be
nice to have an option to tell the scrubber to skip deletion of images
that are currently in use, which is fairly trivial to check for and
provides a nice measure of protection.

Without delay_delete enabled, checking for images in use likely takes
too much time, so this would be limited to just images that are scrubbed
with delay_delete.

I wanted to bring this up here before I go to the trouble of writing a
spec for it, particularly since it doesn't appear that glance currently
talks to Nova as a client at all. Is this something that folks would be
interested in having? Thanks!

--
Chris St. Pierre


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--
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Email: flw...@catalyst.net.nzmailto:flw...@catalyst.net.nz
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Re: [openstack-dev] [glance] Option to skip deleting images in use?

2014-12-16 Thread Collins, Sean
On Tue, Dec 16, 2014 at 05:12:31PM EST, Chris St. Pierre wrote:
 No, I'm looking to prevent images that are in use from being deleted. In
 use and protected are disjoint sets.

I have seen multiple cases of images (and snapshots) being deleted while
still in use in Nova, which leads to some very, shall we say,
interesting bugs and support problems.

I do think that we should try and determine a way forward on this, they
are indeed disjoint sets. Setting an image as protected is a proactive
measure, we should try and figure out a way to keep tenants from
shooting themselves in the foot if possible.

-- 
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Re: [openstack-dev] [glance] Option to skip deleting images in use?

2014-12-16 Thread Vishvananda Ishaya
A simple solution that wouldn’t require modification of glance would be a cron 
job
that lists images and snapshots and marks them protected while they are in use.

Vish

On Dec 16, 2014, at 3:19 PM, Collins, Sean sean_colli...@cable.comcast.com 
wrote:

 On Tue, Dec 16, 2014 at 05:12:31PM EST, Chris St. Pierre wrote:
 No, I'm looking to prevent images that are in use from being deleted. In
 use and protected are disjoint sets.
 
 I have seen multiple cases of images (and snapshots) being deleted while
 still in use in Nova, which leads to some very, shall we say,
 interesting bugs and support problems.
 
 I do think that we should try and determine a way forward on this, they
 are indeed disjoint sets. Setting an image as protected is a proactive
 measure, we should try and figure out a way to keep tenants from
 shooting themselves in the foot if possible.
 
 -- 
 Sean M. Collins
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