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[openstack-dev] [ptl][tc] Accessible upgrade support

0 votes

I'm hoping this will get a little more attention.

We recently started discussing removing governance tags that did not have any
projects asserting them. I think this makes a lot of sense. Some tags were
defined apparently in the hope that it would get projects thinking about them
and wanting to either apply for the tag, or do the work to be able to meet the
requirements for that tag.

While this may have worked in some cases, we do have a few that are a little
unclear and not really getting much attention. We will likely clean up that
tag list a little, but there was some push back on at least one tag.

The supports-accessible-upgrade tag basically states that a service can be
upgraded without affecting access to the resources that the service manages
[1]. This actually fits with how at least Nova and Cinder work, so a patch is
now out there to assert this for those two projects [2].

I would bet there are several other projects out there that work in this same
way. Since we are looking between removing tags or using them (use it or lose
it), I would actually love to see more projects asserting this tag. If your
project manages a set of resources that are available even when your service
is down and/or being upgraded, please consider submitting a patch like [2] to
add your project to the list.

And just a general call out to raise awareness - please take a look through
the other defined tags and see if there are any others that are applicable to
your projects [3].

Thanks!

Sean (smcginnis)

[1] https://governance.openstack.org/tc/reference/tags/assert_supports-accessible-upgrade.html
[2] https://review.openstack.org/#/c/509170/
[3] https://governance.openstack.org/tc/reference/tags/index.html


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asked Oct 7, 2017 in openstack-dev by Sean_McGinnis (11,820 points)   2 2 5

12 Responses

0 votes

On Tue, Oct 3, 2017 at 7:52 PM, Sean McGinnis sean.mcginnis@gmx.com wrote:
I'm hoping this will get a little more attention.

We recently started discussing removing governance tags that did not have any
projects asserting them. I think this makes a lot of sense. Some tags were
defined apparently in the hope that it would get projects thinking about them
and wanting to either apply for the tag, or do the work to be able to meet the
requirements for that tag.

While this may have worked in some cases, we do have a few that are a little
unclear and not really getting much attention. We will likely clean up that
tag list a little, but there was some push back on at least one tag.

The supports-accessible-upgrade tag basically states that a service can be
upgraded without affecting access to the resources that the service manages
[1]. This actually fits with how at least Nova and Cinder work, so a patch is
now out there to assert this for those two projects [2].

I would bet there are several other projects out there that work in this same
way. Since we are looking between removing tags or using them (use it or lose
it), I would actually love to see more projects asserting this tag. If your
project manages a set of resources that are available even when your service
is down and/or being upgraded, please consider submitting a patch like [2] to
add your project to the list.

And just a general call out to raise awareness - please take a look through
the other defined tags and see if there are any others that are applicable to
your projects [3].

Thanks!

Sean (smcginnis)

[1] https://governance.openstack.org/tc/reference/tags/assert_supports-accessible-upgrade.html
[2] https://review.openstack.org/#/c/509170/
[3] https://governance.openstack.org/tc/reference/tags/index.html


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Hello,

I like the idea.

A few comments, I don't know if it's too late for that, but I shoot anyway:

  • I don't see any mention of documentation in the required steps to
    get this governance tag.
    I think it can serve the community better if we enforce the
    inclusion of the documentation on
    'HOW to trigger this "accessible" upgrade'. What do you think?
  • As part of a deployment project team, I like the fact it's easy for
    us (and for our users)
    to see which service is behaving "accessibly".
    It sets expectations, both for us and for the deployers.

I have questions on that "expectations" part: Would you like the
deployment projects apply for those tags?
How do you see that going? What are the requirements we have to match
for a deployment project
to be considered "upgrade accessible" ?

In my opinion it should be something along the lines of:
"if an upstream "accessible" project is deployed, it should be
upgraded in an "accessible" way,
while non "accessible" projects would fallback to a standard
'supporting upgrade' pattern?"

Or alternatively, we don't apply this tag to deployment projects.
Opinion?


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responded Oct 4, 2017 by Jean-Philippe_Evrard (1,360 points)   2
0 votes

On Wed, Oct 04, 2017 at 02:07:53PM +0100, Jean-Philippe Evrard wrote:

  • I don't see any mention of documentation in the required steps to
    get this governance tag.
    I think it can serve the community better if we enforce the
    inclusion of the documentation on
    'HOW to trigger this "accessible" upgrade'. What do you think?
  • As part of a deployment project team, I like the fact it's easy for
    us (and for our users)
    to see which service is behaving "accessibly".
    It sets expectations, both for us and for the deployers.

That's a good point. I think for Nova and Cinder (the only two being looked at
so far), there aren't any special steps to achieve this. Other than not
rebooting the host instead of just restarting services.

If a project does need extra precautions taken, then I agree that should be
part of this that it is documented somewhere. Would you like to add some text
stating that to the Requirements section? [1]

[1] https://git.openstack.org/cgit/openstack/governance/tree/reference/tags/assert_supports-accessible-upgrade.rst

I have questions on that "expectations" part: Would you like the
deployment projects apply for those tags?
How do you see that going? What are the requirements we have to match
for a deployment project
to be considered "upgrade accessible" ?

In my opinion it should be something along the lines of:
"if an upstream "accessible" project is deployed, it should be
upgraded in an "accessible" way,
while non "accessible" projects would fallback to a standard
'supporting upgrade' pattern?"

Or alternatively, we don't apply this tag to deployment projects.
Opinion?

Another good question! There is some discussion going on right now on whether
any of these tags really apply to deployment projects. I think service projects
were really what was in mind when they were created, whether intentionally or
not. Applying it to mean that accessible projects are deployed accessibly by a
deployment tool kind of makes sense, but I would be concerned we would hit
some situation where it doesn't quite fit like we have with the stable policy
tag.

I think that needs more discussion for sure.


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responded Oct 4, 2017 by Sean_McGinnis (11,820 points)   2 2 5
0 votes

On 10/3/2017 1:52 PM, Sean McGinnis wrote:
I'm hoping this will get a little more attention.

We recently started discussing removing governance tags that did not have any
projects asserting them. I think this makes a lot of sense. Some tags were
defined apparently in the hope that it would get projects thinking about them
and wanting to either apply for the tag, or do the work to be able to meet the
requirements for that tag.

While this may have worked in some cases, we do have a few that are a little
unclear and not really getting much attention. We will likely clean up that
tag list a little, but there was some push back on at least one tag.

The supports-accessible-upgrade tag basically states that a service can be
upgraded without affecting access to the resources that the service manages
[1]. This actually fits with how at least Nova and Cinder work, so a patch is
now out there to assert this for those two projects [2].

I would bet there are several other projects out there that work in this same
way. Since we are looking between removing tags or using them (use it or lose
it), I would actually love to see more projects asserting this tag. If your
project manages a set of resources that are available even when your service
is down and/or being upgraded, please consider submitting a patch like [2] to
add your project to the list.

And just a general call out to raise awareness - please take a look through
the other defined tags and see if there are any others that are applicable to
your projects [3].

Thanks!

Sean (smcginnis)

[1] https://governance.openstack.org/tc/reference/tags/assert_supports-accessible-upgrade.html
[2] https://review.openstack.org/#/c/509170/
[3] https://governance.openstack.org/tc/reference/tags/index.html


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What's the difference between this tag and the zero-impact-upgrades tag?
I guess the accessible one is, can a user still ssh into their VM while
the nova compute service is being upgraded. The zero-impact-upgrade one
is more to do with performance degradation during an upgrade. I'm not
entirely sure what that might look like, probably need operator input.
For example, while upgrading, you're live migrating VMs all over the
place which is putting extra strain on the network.

I think all of the tags could benefit from some examples for real use
cases so people have context when reading them.

Also, does the Foundation have any data on how much tags are used as
input to weigh decisions about choosing to adopt an OpenStack project in
a deployment or not? I'm not entirely sure what the carrot and stick is
with tags or if/how people are consuming them. I don't ever think about
tags personally, probably because there is no bi-annual audit process on
them to see if we need to add/remove tags from nova.

--

Thanks,

Matt


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responded Oct 4, 2017 by mriedemos_at_gmail.c (15,720 points)   2 4 9
0 votes

Matt Riedemann mriedemos@gmail.com
October 4, 2017 at 10:51 AM

What's the difference between this tag and the zero-impact-upgrades
tag? I guess the accessible one is, can a user still ssh into their VM
while the nova compute service is being upgraded. The
zero-impact-upgrade one is more to do with performance degradation
during an upgrade. I'm not entirely sure what that might look like,
probably need operator input. For example, while upgrading, you're
live migrating VMs all over the place which is putting extra strain on
the network.

I think all of the tags could benefit from some examples for real use
cases so people have context when reading them.
We do provide tag definitions. They're linked from the Project Navigator
(e.g.
https://docs.openstack.org/project-team-guide/stable-branches.html).
These provide pretty thorough definitions, and in some cases examples. I
like the idea of having additional examples per project and that's
something we could easily put into the Project Navigator.

Also, does the Foundation have any data on how much tags are used as
input to weigh decisions about choosing to adopt an OpenStack project
in a deployment or not?
One could probably make this inference based around user survey data +
which tags are used in the more vs. less popular projects. Right now,
it's not something we track, but it's an interesting point. I'll spend
some time looking at it :)
I'm not entirely sure what the carrot and stick is with tags or if/how
people are consuming them. I don't ever think about tags personally,
probably because there is no bi-annual audit process on them to see if
we need to add/remove tags from nova.
It's a good point. So far the biggest carrot is to make sure your
project stats look as up to date as other mature and well adopted
projects. To date, it seems to have had a positive impact in getting
projects to keep their tags updated and/or figure out what they need to
do to get the tag.

Sean McGinnis sean.mcginnis@gmx.com
October 3, 2017 at 1:52 PM
I'm hoping this will get a little more attention.

We recently started discussing removing governance tags that did not
have any
projects asserting them. I think this makes a lot of sense. Some tags were
defined apparently in the hope that it would get projects thinking
about them
and wanting to either apply for the tag, or do the work to be able to
meet the
requirements for that tag.

While this may have worked in some cases, we do have a few that are a
little
unclear and not really getting much attention. We will likely clean up
that
tag list a little, but there was some push back on at least one tag.

The supports-accessible-upgrade tag basically states that a service can be
upgraded without affecting access to the resources that the service
manages
[1]. This actually fits with how at least Nova and Cinder work, so a
patch is
now out there to assert this for those two projects [2].

I would bet there are several other projects out there that work in
this same
way. Since we are looking between removing tags or using them (use it
or lose
it), I would actually love to see more projects asserting this tag. If
your
project manages a set of resources that are available even when your
service
is down and/or being upgraded, please consider submitting a patch like
[2] to
add your project to the list.

And just a general call out to raise awareness - please take a look
through
the other defined tags and see if there are any others that are
applicable to
your projects [3].

Thanks!

Sean (smcginnis)

[1]
https://governance.openstack.org/tc/reference/tags/assert_supports-accessible-upgrade.html
[2] https://review.openstack.org/#/c/509170/
[3] https://governance.openstack.org/tc/reference/tags/index.html


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responded Oct 4, 2017 by jimmy_at_openstack.o (3,120 points)   1 2
0 votes

Matt Riedemann wrote:
What's the difference between this tag and the zero-impact-upgrades tag?
I guess the accessible one is, can a user still ssh into their VM while
the nova compute service is being upgraded. The zero-impact-upgrade one
is more to do with performance degradation during an upgrade. I'm not
entirely sure what that might look like, probably need operator input.
For example, while upgrading, you're live migrating VMs all over the
place which is putting extra strain on the network.

The zero-impact-upgrade tag means no API downtime and no measurable
impact on performance, while the accessible-upgrade means that while
there can be API downtime, the resources provisioned are still
accessible (you can use the VM even if nova-api is down).

I still think we have too many of those upgrade tags, and amount of
information they provide does not compensate the confusion they create.
If you're not clear on what they mean, imagine a new user looking at the
Software Navigator...

In particular, we created two paths in the graph:
* upgrade < accessible-upgrade
* upgrade < rolling-upgrade < zero-downtime < zero-impact

I personally would get rid of zero-impact (not sure there is that much
additional information it conveys beyond zero-downtime).

If we could make the requirements of accessible-upgrade a part of
rolling-upgrade, that would also help (single path in the graph, only 3
"levels"). Is there any of the current rolling-upgrade things (cinder,
neutron, nova, swift) that would not qualify for accessible-upgrade as
well ?

--
Thierry Carrez (ttx)


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responded Oct 5, 2017 by Thierry_Carrez (57,480 points)   3 8 13
0 votes

On Thu, 5 Oct 2017, at 09:50, Thierry Carrez wrote:
Matt Riedemann wrote:

What's the difference between this tag and the zero-impact-upgrades tag?
I guess the accessible one is, can a user still ssh into their VM while
the nova compute service is being upgraded. The zero-impact-upgrade one
is more to do with performance degradation during an upgrade. I'm not
entirely sure what that might look like, probably need operator input.
For example, while upgrading, you're live migrating VMs all over the
place which is putting extra strain on the network.

The zero-impact-upgrade tag means no API downtime and no measurable
impact on performance, while the accessible-upgrade means that while
there can be API downtime, the resources provisioned are still
accessible (you can use the VM even if nova-api is down).

I still think we have too many of those upgrade tags, and amount of
information they provide does not compensate the confusion they create.
If you're not clear on what they mean, imagine a new user looking at the
Software Navigator...

In particular, we created two paths in the graph:
* upgrade < accessible-upgrade
* upgrade < rolling-upgrade < zero-downtime < zero-impact

I personally would get rid of zero-impact (not sure there is that much
additional information it conveys beyond zero-downtime).

If we could make the requirements of accessible-upgrade a part of
rolling-upgrade, that would also help (single path in the graph, only 3
"levels"). Is there any of the current rolling-upgrade things (cinder,
neutron, nova, swift) that would not qualify for accessible-upgrade as
well ?

Well, there is projects (like designate) that qualify for accessible
upgrade, but not rolling upgrade.

--
Thierry Carrez (ttx)


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responded Oct 5, 2017 by gr_at_ham.ie (620 points)  
0 votes

On 10/05/2017 07:08 AM, Graham Hayes wrote:

On Thu, 5 Oct 2017, at 09:50, Thierry Carrez wrote:

Matt Riedemann wrote:

What's the difference between this tag and the zero-impact-upgrades tag?
I guess the accessible one is, can a user still ssh into their VM while
the nova compute service is being upgraded. The zero-impact-upgrade one
is more to do with performance degradation during an upgrade. I'm not
entirely sure what that might look like, probably need operator input.
For example, while upgrading, you're live migrating VMs all over the
place which is putting extra strain on the network.

The zero-impact-upgrade tag means no API downtime and no measurable
impact on performance, while the accessible-upgrade means that while
there can be API downtime, the resources provisioned are still
accessible (you can use the VM even if nova-api is down).

I still think we have too many of those upgrade tags, and amount of
information they provide does not compensate the confusion they create.
If you're not clear on what they mean, imagine a new user looking at the
Software Navigator...

In particular, we created two paths in the graph:
* upgrade < accessible-upgrade
* upgrade < rolling-upgrade < zero-downtime < zero-impact

I personally would get rid of zero-impact (not sure there is that much
additional information it conveys beyond zero-downtime).

If we could make the requirements of accessible-upgrade a part of
rolling-upgrade, that would also help (single path in the graph, only 3
"levels"). Is there any of the current rolling-upgrade things (cinder,
neutron, nova, swift) that would not qualify for accessible-upgrade as
well ?

Well, there is projects (like designate) that qualify for accessible
upgrade, but not rolling upgrade.

The neutron story is mixed on accessable upgrade, because at least in
some cases, like ovs, upgrade might trigger a network tear down /
rebuild that generates an outage (though typically a pretty small one).

I still think it's hard to describe to folks what is going on without
pictures. And the tag structure might just be the wrong way to describe
the world, because they are a set of positive assertions, and upgrade
expectations are really about: "how terrible will this be".

If I was an operator the questions I might have is:

1) Really basic, will my db roll forward?

2) When my db rolls forward, is it going to take a giant table lock that
is effectively an outage?

3) Is whatever date I created, computes, networks going to stay up when
I do all this? (i.e. no customer workload interuption)

4) If the service is more than 1 process, can they arbitrarily work with
N-1 so I won't have a closet outage when services restart.

5) If the service runs on more than 1 host, can I mix host levels, or
will there be an outage as I upgrade nodes

6) If the service talks to other openstack services, is there a strict
version lock in which means I've got to coordinate with those for
upgrade? If so, what order is that and is it clear?

7) Can I seamlessly hide my API upgrade behind HA-Proxy / Istio / (or
similar) so that there is no API service interruption

8) Is there any substantial degradation in running "mixed mode" even if
it's supported, so that I know whether I can do this over a longer
window of time when time permits

9) What level of validation exists to ensure that any of these "should
work" do work?

The tags were really built around grouping a few of these, but even with
folks that are near the problem, they got confusing quick. I really
think that some more pictoral upgrade safety cards or something
explaining the things you need to consider, and what parts projects
handle for you would be really useful. And then revisit whatever the
tagging structure is going to be later.

-Sean

--
Sean Dague
http://dague.net


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responded Oct 5, 2017 by Sean_Dague (66,200 points)   4 8 14
0 votes

Graham Hayes wrote:
On Thu, 5 Oct 2017, at 09:50, Thierry Carrez wrote:

[...]
In particular, we created two paths in the graph:
* upgrade < accessible-upgrade
* upgrade < rolling-upgrade < zero-downtime < zero-impact

I personally would get rid of zero-impact (not sure there is that much
additional information it conveys beyond zero-downtime).

If we could make the requirements of accessible-upgrade a part of
rolling-upgrade, that would also help (single path in the graph, only 3
"levels"). Is there any of the current rolling-upgrade things (cinder,
neutron, nova, swift) that would not qualify for accessible-upgrade as
well ?

Well, there is projects (like designate) that qualify for accessible
upgrade, but not rolling upgrade.

Sure, but is there real user value in communicating that capability
separately from the rolling-upgrade ability ? And if there is value, is
it enough to justify creating a harder-to-decipher upgrade tag landscape ?

The fact that you didn't apply for the tag yet points to the limited
value of it...

--
Thierry Carrez (ttx)


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responded Oct 5, 2017 by Thierry_Carrez (57,480 points)   3 8 13
0 votes

Sean Dague wrote:
[...]
I still think it's hard to describe to folks what is going on without
pictures. And the tag structure might just be the wrong way to describe
the world, because they are a set of positive assertions, and upgrade
expectations are really about: "how terrible will this be".

If I was an operator the questions I might have is:
[...]

The tags were really built around grouping a few of these, but even with
folks that are near the problem, they got confusing quick. I really
think that some more pictoral upgrade safety cards or something
explaining the things you need to consider, and what parts projects
handle for you would be really useful. And then revisit whatever the
tagging structure is going to be later.

Good point. Maybe the upgrade functionality is critical enough to
warrant its own data set, and using a set of binary tags is not the best
way to capture it.

--
Thierry Carrez (ttx)


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responded Oct 5, 2017 by Thierry_Carrez (57,480 points)   3 8 13
0 votes

The neutron story is mixed on accessable upgrade, because at least in some
cases, like ovs, upgrade might trigger a network tear down / rebuild that
generates an outage (though typically a pretty small one).

This shouldn't happen. If it does it should be reported as a bug. All
existing OVS flows are left in place during agent initialization and we
don't get rid of the old ones until the agent finishes setting up the new
ones.

On Thu, Oct 5, 2017 at 4:42 AM, Sean Dague sean@dague.net wrote:

On 10/05/2017 07:08 AM, Graham Hayes wrote:

On Thu, 5 Oct 2017, at 09:50, Thierry Carrez wrote:

Matt Riedemann wrote:

What's the difference between this tag and the zero-impact-upgrades
tag?
I guess the accessible one is, can a user still ssh into their VM while
the nova compute service is being upgraded. The zero-impact-upgrade one
is more to do with performance degradation during an upgrade. I'm not
entirely sure what that might look like, probably need operator input.
For example, while upgrading, you're live migrating VMs all over the
place which is putting extra strain on the network.

The zero-impact-upgrade tag means no API downtime and no measurable
impact on performance, while the accessible-upgrade means that while
there can be API downtime, the resources provisioned are still
accessible (you can use the VM even if nova-api is down).

I still think we have too many of those upgrade tags, and amount of
information they provide does not compensate the confusion they create.
If you're not clear on what they mean, imagine a new user looking at the
Software Navigator...

In particular, we created two paths in the graph:
* upgrade < accessible-upgrade
* upgrade < rolling-upgrade < zero-downtime < zero-impact

I personally would get rid of zero-impact (not sure there is that much
additional information it conveys beyond zero-downtime).

If we could make the requirements of accessible-upgrade a part of
rolling-upgrade, that would also help (single path in the graph, only 3
"levels"). Is there any of the current rolling-upgrade things (cinder,
neutron, nova, swift) that would not qualify for accessible-upgrade as
well ?

Well, there is projects (like designate) that qualify for accessible
upgrade, but not rolling upgrade.

The neutron story is mixed on accessable upgrade, because at least in
some cases, like ovs, upgrade might trigger a network tear down /
rebuild that generates an outage (though typically a pretty small one).

I still think it's hard to describe to folks what is going on without
pictures. And the tag structure might just be the wrong way to describe
the world, because they are a set of positive assertions, and upgrade
expectations are really about: "how terrible will this be".

If I was an operator the questions I might have is:

1) Really basic, will my db roll forward?

2) When my db rolls forward, is it going to take a giant table lock that
is effectively an outage?

3) Is whatever date I created, computes, networks going to stay up when
I do all this? (i.e. no customer workload interuption)

4) If the service is more than 1 process, can they arbitrarily work with
N-1 so I won't have a closet outage when services restart.

5) If the service runs on more than 1 host, can I mix host levels, or
will there be an outage as I upgrade nodes

6) If the service talks to other openstack services, is there a strict
version lock in which means I've got to coordinate with those for
upgrade? If so, what order is that and is it clear?

7) Can I seamlessly hide my API upgrade behind HA-Proxy / Istio / (or
similar) so that there is no API service interruption

8) Is there any substantial degradation in running "mixed mode" even if
it's supported, so that I know whether I can do this over a longer
window of time when time permits

9) What level of validation exists to ensure that any of these "should
work" do work?

The tags were really built around grouping a few of these, but even with
folks that are near the problem, they got confusing quick. I really
think that some more pictoral upgrade safety cards or something
explaining the things you need to consider, and what parts projects
handle for you would be really useful. And then revisit whatever the
tagging structure is going to be later.

    -Sean

--
Sean Dague
http://dague.net


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responded Oct 6, 2017 by kevin_at_benton.pub (15,600 points)   2 3 4
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