<html>
<head>
<meta content="text/html; charset=windows-1252"
http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<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 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 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
<meta http-equiv="content-type" content="text/html;
charset=windows-1252">
<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>
[1] <a class="moz-txt-link-freetext" href="https://bugs.launchpad.net/nova/+bug/1158684">https://bugs.launchpad.net/nova/+bug/1158684</a><br>
[2] <a class="moz-txt-link-freetext" href="https://review.openstack.org/#/c/130093/">https://review.openstack.org/#/c/130093/</a><br>
[3] <a class="moz-txt-link-freetext" href="https://bugs.launchpad.net/heat/+bug/1301486">https://bugs.launchpad.net/heat/+bug/1301486</a><br>
</body>
</html>