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<div class="moz-cite-prefix">On 29/10/14 09:28, Steve Baker wrote:<br>
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<blockquote cite="mid:544FFC66.5030302@redhat.com" type="cite">
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<div class="moz-cite-prefix">On 29/10/14 06:51, Steven Hardy
wrote:<br>
</div>
<blockquote cite="mid:20141028175137.GA24121@t430slt.redhat.com"
type="cite">
<pre wrap="">Hi all,
So I've been investigating bug #1383709, which has caused me to run into a
bad update pattern involving OS::Neutron::Port
<a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://docs.openstack.org/developer/heat/template_guide/openstack.html#OS::Neutron::Port">http://docs.openstack.org/developer/heat/template_guide/openstack.html#OS::Neutron::Port</a>
I'm not quite clear on the history, but for some reason, we have a
"replacement_policy" property, unlike all other resources, and it defaults
to replacing the resource every time you update, unless you pass "AUTO" to
the property.
I'm sure there's a good reason for this, but on the face of it, it seems to
be a very unsafe and inconvenient default when considering updates?
The problem (which may actually be the cause the bug #1383709) is the UUID
changes, so you don't only replace the port, you replace it and everything
that references it, which makes the Port resource a landmine of
HARestarter-esque proportions ;)
Can anyone (and in particular stevebaker who initally wrote the code) shed
any light on this? Can we just flip the default to AUTO, as it seems to be
a more desirable default for nearly all users?
Thanks!
</pre>
</blockquote>
The commit does a reasonable job of explaining the whole sorry
situation<br>
<br>
<a moz-do-not-send="true" class="moz-txt-link-freetext"
href="https://review.openstack.org/#/c/121693/">https://review.openstack.org/#/c/121693/</a><br>
<br>
This was an attempt to improve port modelling enough for Juno
while nova bug #1158684 [1] remains unfixed.<br>
<br>
If we defaulted to
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<span style="color: rgb(51, 51, 51); font-family: monospace;
font-size: 11.8181819915771px; font-style: normal; font-variant:
normal; font-weight: normal; letter-spacing: normal;
line-height: 18px; orphans: auto; text-align: left; text-indent:
0px; text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; display:
inline !important; float: none; background-color: rgb(255, 255,
255);">replacement_policy:AUTO</span> then we have the 2 issues
when a server is replaced on stack update [3][1]<br>
<br>
If we keep the current default then we have the symptoms of bug
#1383709.<br>
<br>
Both options suck and there is no way of always doing the right
thing, which is why <span style="color: rgb(51, 51, 51);
font-family: monospace; font-size: 11.8181819915771px;
font-style: normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: 18px; orphans: auto;
text-align: left; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px; display: inline !important;
float: none; background-color: rgb(255, 255, 255);">replacement_policy</span>
exists - to push this decision to the template author.<br>
<br>
I've come to the conclusion that ports shouldn't be modelled as
resources at all; they sometimes represent exclusive resources
(fixed IPs) and their dependencies with servers sometimes goes
both ways. To fix this properly I've written a Kilo spec for
blueprint rich-network-prop [2]<br>
<br>
Before we switch the default to AUTO maybe we could investigate
getting REPLACE_ALWAYS to interact better with ResourceGroup (or
the tripleo templates which use it)<br>
<br>
</blockquote>
<br>
I've looked at the tripleo templates now, and they create ports
which are resources in their own right, so switching to
replacement_policy:AUTO is entirely appropriate. However in most
templates the vast majority of port resources are just to define a
simple server/port/floating-IP combo. Therefore I think there is a
good argument for the default REPLACE_ALWAYS causing the least
problems for the majority of cases.<br>
<br>
<blockquote cite="mid:544FFC66.5030302@redhat.com" type="cite"> [1]
<a moz-do-not-send="true" class="moz-txt-link-freetext"
href="https://bugs.launchpad.net/nova/+bug/1158684">https://bugs.launchpad.net/nova/+bug/1158684</a><br>
[2] <a moz-do-not-send="true" class="moz-txt-link-freetext"
href="https://review.openstack.org/#/c/130093/">https://review.openstack.org/#/c/130093/</a><br>
[3] <a moz-do-not-send="true" class="moz-txt-link-freetext"
href="https://bugs.launchpad.net/heat/+bug/1301486">https://bugs.launchpad.net/heat/+bug/1301486</a><br>
<br>
</blockquote>
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