<div dir="ltr"><p style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-indent:36pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">Hello, Stackers.<br>
</span></p><p style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-indent:36pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline"><br>
</span></p><p style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-indent:36pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">I’d like to discuss guestagent prepare call polling mechanism issue (see [1]).</span></p>
<br><p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-indent:36pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">Let
me first describe why this is actually an issue and why it should be
fixed. For those of you who is familiar with Trove knows that Trove can
provision instances through Nova API and Heat API (see [2] and see [3]).</span></p>
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline"> </span></p>
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline"> </span><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">What’s the difference between this two ways (in general)? The answer is simple:</span></p>
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-indent:36pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">-
Heat-based provisioning method has polling mechanism that verifies that
stack provisioning was completed with successful state (see [4]) which
means that all stack resources are in ACTIVE state.</span></p>
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-indent:36pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">-
Nova-based provisioning method doesn’t do any polling (which is wrong,
since instance can’t fail as fast as possible because Trove-taskmanager
service doesn’t verify that launched server had reached ACTIVE state.
That’s the issue #1 - compute instance state is unknown, but</span><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline"> right after resources (deliverd by heat) already in ACTIVE states.<br>
</span></p><br><p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-indent:36pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">Once
one method [2] or [3] finished, taskmanager trying to prepare data for
guest (see [5]) and then it tries to send prepare call to guest (see
[6]). Here comes issue #2 - polling mechanism does at least 100 API
calls to Nova to define compute instance status.</span></p>
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-indent:36pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">Also taskmanager does almost the same amount of calls to Trove backend to discover guest status which is totally normal.</span></p>
<br><p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline"> </span><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">So,
here comes the question, why should i call 99 times Nova for the same
value if the value asked for the first time was completely acceptable?</span></p>
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline"> </span></p>
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline"> </span><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">There’s
only one way to fix it. Since heat-based provisioning delivers instance
with status validation procedure, the same thing should be done for
nova-base provisioning (we should extract compute instance status
polling from guest prepare polling mechanism and integrate it into [2])
and leave only guest status discovering in guest prepare polling
mechanism.</span></p>
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline"> </span></p>
<br><br><p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-indent:36pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">Benefits?
Proposed fix will give an ability for fast-failing for corrupted
instances, it would reduce amount of redundant Nova API calls while
attempting to discover guest status.</span></p>
<br><br><p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-indent:36pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">Proposed fix for this issue - [7].</span></p>
<br><p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">[1] - </span><a href="https://launchpad.net/bugs/1325512" style="text-decoration:none" target="_blank"><span style="font-size:15px;font-family:Arial;color:rgb(17,85,204);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:underline;vertical-align:baseline">https://launchpad.net/bugs/1325512</span></a></p>
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">[2] - </span><a href="https://github.com/openstack/trove/blob/master/trove/taskmanager/models.py#L198-L215" style="text-decoration:none" target="_blank"><span style="font-size:15px;font-family:Arial;color:rgb(17,85,204);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:underline;vertical-align:baseline">https://github.com/openstack/trove/blob/master/trove/taskmanager/models.py#L198-L215</span></a></p>
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">[3] - </span><a href="https://github.com/openstack/trove/blob/master/trove/taskmanager/models.py#L190-L197" style="text-decoration:none" target="_blank"><span style="font-size:15px;font-family:Arial;color:rgb(17,85,204);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:underline;vertical-align:baseline">https://github.com/openstack/trove/blob/master/trove/taskmanager/models.py#L190-L197</span></a></p>
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">[4] - </span><a href="https://github.com/openstack/trove/blob/master/trove/taskmanager/models.py#L420-L429" style="text-decoration:none" target="_blank"><span style="font-size:15px;font-family:Arial;color:rgb(17,85,204);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:underline;vertical-align:baseline">https://github.com/openstack/trove/blob/master/trove/taskmanager/models.py#L420-L429</span></a></p>
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">[5] - </span><a href="https://github.com/openstack/trove/blob/master/trove/taskmanager/models.py#L217-L256" style="text-decoration:none" target="_blank"><span style="font-size:15px;font-family:Arial;color:rgb(17,85,204);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:underline;vertical-align:baseline">https://github.com/openstack/trove/blob/master/trove/taskmanager/models.py#L217-L256</span></a></p>
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">[6] - </span><a href="https://github.com/openstack/trove/blob/master/trove/taskmanager/models.py#L254-L266" style="text-decoration:none" target="_blank"><span style="font-size:15px;font-family:Arial;color:rgb(17,85,204);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:underline;vertical-align:baseline">https://github.com/openstack/trove/blob/master/trove/taskmanager/models.py#L254-L266</span></a></p>
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">[7] - </span><a href="https://review.openstack.org/#/c/97194/" style="text-decoration:none" target="_blank"><span style="font-size:15px;font-family:Arial;color:rgb(17,85,204);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:underline;vertical-align:baseline">https://review.openstack.org/#/c/97194/</span></a></p>
<br><br><p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">Thoughts?</span></p>
<br><p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">Best regards,</span></p>
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt;text-align:justify"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">Denis Makogon</span></p>
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