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float: none;">Thanks HU yanyan, I still has some questions about
your answers, and I respond inline.</span><br>
<br>
<div class="moz-cite-prefix">On 2015/11/23 10:43, Yanyan Hu wrote:<br>
</div>
<blockquote
cite="mid:CAPnJsYCnBW=vznwuS_f1TO8QccLO93QLCGdrg=3FoNpZ4H0fzw@mail.gmail.com"
type="cite">
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<div dir="ltr">Hi, Xu Jun, please find some answers inline.
Thanks.<br>
<br>
<div class="gmail_extra"><br>
<div class="gmail_quote"><span class="">2015-11-20 16:06
GMT+08:00 <a moz-do-not-send="true"
href="mailto:xujun@cmss.chinamobile.com"
target="_blank">xujun@cmss.chinamobile.com</a> <span
dir="ltr"><<a moz-do-not-send="true"
href="mailto:xujun@cmss.chinamobile.com"
target="_blank">xujun@cmss.chinamobile.com</a>></span>:<br>
<blockquote class="gmail_quote" style="margin:0px 0px
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rgb(204,204,204);padding-left:1ex">
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<div><font color="#ff0000">Thanks
yanyan!</font></div>
<span>
<div><br>
</div>
Xu Jun is a contributor from CMCC. He
asked a very interesting question
about cluster scaling support in
Senlin. To make the discussion more
thorough, I just post the question and
my answer here.<br>
<br>
</span></div>
<span>The question from Jun is as
following:<br>
<br>
For an action, senlin will check all
according polices, like if a cluster
attach two scaling-in polices, <br>
the two scaling-in polices will be
checked when doing a scaling-action on
this cluster. This is not same as
OS::Heat::ScalingPolicy in heat？<br>
How should I use senlin for following
cases？<br>
1. 15% < cpu_util < 30%,
scaling_in 1 instance<br>
2. cpu_util < 15%, scaling_in 2
instances<br>
<br>
This is a very interesting question and
you're right about the difference
between Senlin ScalingPolicy and
OS::Heat::ScalingPolicy. In Heat,
OS::Heat::ScalingPolicy is actually not
just a policy. It is a combination of a
webhook and a rule about how ASG respond
to the webhook triggering(resource
signal). So you can define two different
OS::Heat::ScalingPolicy instances to
make them deal with two cases you
described respectively.<br>
<br>
But in Senlin, ScalingPolicy is a REAL
policy, it only describes how a Senlin
cluster react to an action triggered by
Senlin webhook which is defined
separately. The problem is when an
cluster action e.g. CLUSTER_SCALE_IN is
triggered, all policies attached to it
will be checked in sequence based on
policies priority definition.<strike> </strike><u><font
color="#ff9900">So if you create two
Senlin ScalingPolicy and attach them
to the same cluster, only one of
them will take effect actually.</font></u></span></div>
<div><u><font color="#ff9900"><br>
</font></u></div>
<div><font color="#0000ff"># 1. But in
policy_check function, all the policies
will be checked in priority-based order
for a CLUSTER_SCALING_IN action if the
cluster attached with SCALING multiple
policies. </font></div>
<div><font color="#0000ff"> is this a
bug? or what <span
style="font-size:10.5pt;line-height:1.5;background-color:window"> is
the </span><span
style="font-family:"";font-size:10.5pt;line-height:1.5;background-color:window">significance</span><font
style="font-size:10.5pt;line-height:1.5;background-color:window"><span
style="font-size:10.5pt;line-height:1.5;background-color:window">
of prority</span></font></font><span
style="font-size:10.5pt;line-height:1.5;background-color:window;color:rgb(0,0,255)">).
</span></div>
</div>
</div>
</blockquote>
</div>
</blockquote>
</span>
<div> <span style="color:rgb(255,0,0)"><span
style="background-color:rgb(255,255,255)">
<i>Sorry, I didn't describe it clearly. I mean
although both scaling policies will be checked
before CLUSTER_SCALING_IN action is executed,
count result from one ScalingPolicy will
actually be overridden by the result from
another ScalingPolicy which has higher priority.</i></span></span><br>
</div>
</div>
</div>
</div>
</div>
</div>
</blockquote>
<br>
<font color="#3333ff"><font face="\Microsoft YaHei UI\"><font
color="#000000">After debugging<font face="\Microsoft YaHei
UI\">,</font> I found that former result is not overridden
by another policy.</font><br>
<font color="#000000"><a class="moz-txt-link-freetext" href="http://git.openstack.org/cgit/openstack/senlin/tree/senlin/engine/actions/base.py#n441">http://git.openstack.org/cgit/openstack/senlin/tree/senlin/engine/actions/base.py#n441</a><br>
<br>
</font></font></font>
<blockquote
cite="mid:CAPnJsYCnBW=vznwuS_f1TO8QccLO93QLCGdrg=3FoNpZ4H0fzw@mail.gmail.com"
type="cite">
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<div> <br>
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<div><font color="#0000ff"> 2. if a
cluster attached a scaling policy with
event = <span
style="font-family:"";font-size:10.5pt;line-height:1.5;background-color:window">CLUSTER_SCALE_IN,
when a</span><font
style="font-size:10.5pt;line-height:1.5;background-color:window"> </font><span
style="font-size:10.5pt;line-height:1.5;background-color:window">CLUSTER_SCALING_OUT
</span><span
style="font-size:10.5pt;line-height:1.5;background-color:window">action
is triggered, the policy also will be
checked, is this reasonable?</span></font></div>
</div>
</div>
</blockquote>
</div>
</blockquote>
</span>
<div><span style="color:rgb(255,0,0)"><i> When a
ScalingPolicy is defined, you can use 'event'
property to specify the action type you want the
policy to take effect on, like:<br>
<a moz-do-not-send="true"
href="http://git.openstack.org/cgit/openstack/senlin/tree/examples/policies/scaling_policy.yaml#n5"
target="_blank">http://git.openstack.org/cgit/openstack/senlin/tree/examples/policies/scaling_policy.yaml#n5</a><br>
<br>
Although a ScalingPolicy will be checked
for both CLUSTER_SCALE_IN and CLUSTER_SCALE_OUT
actions, the check routine will return immediately
if the action type is not what it is expecting. <br>
<a moz-do-not-send="true"
href="http://git.openstack.org/cgit/openstack/senlin/tree/senlin/policies/scaling_policy.py#n133"
target="_blank">http://git.openstack.org/cgit/openstack/senlin/tree/senlin/policies/scaling_policy.py#n133</a></i></span><br>
</div>
</div>
</div>
</div>
</div>
</div>
</blockquote>
<br>
<font color="#3366ff"><font color="#000000">Yes it's not checked in
pre_op, but all ScalingPolicies still will be checked whether
in cooldown.</font><br>
<font color="#000000"><a class="moz-txt-link-freetext" href="http://git.openstack.org/cgit/openstack/senlin/tree/senlin/engine/actions/base.py#n431">http://git.openstack.org/cgit/openstack/senlin/tree/senlin/engine/actions/base.py#n431</a></font></font><font
color="#3333ff" face="\Microsoft YaHei UI\"><b><span
style="line-height: 1.5;"> <br>
</span></b></font><br>
<blockquote
cite="mid:CAPnJsYCnBW=vznwuS_f1TO8QccLO93QLCGdrg=3FoNpZ4H0fzw@mail.gmail.com"
type="cite">
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<div class="gmail_extra">
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<div>
<div dir="ltr"><span>
<div><br>
<br>
Currently, you can use the following way
to support your use case in Senlin:<br>
1. Define two Senlin webhooks which
target on the CLUSTER_SCALE_OUT action
of the cluster and specify the 'param'
as {'count': 1} for webhook1 and
{'count': 2 } for webhook2;<br>
1. Define two ceilometer/aodh alarms
with the first one matching case1 and
second one matching case2. Then define
webhook1 url as alarm1's alarm-action
and webhook2 url as alarm2's
alarm-action.</div>
<div><br>
</div>
</span>
<div><font color="#0000ff"># </font></div>
<div><font color="#0000ff">Your suggestion
has a problem when I want different
cooldown for each <span
style="font-size:10.5pt;line-height:1.5;background-color:window">ceilometer/aodh </span><span
style="font-size:10.5pt;line-height:1.5;background-color:window">alarms,
for following cases, how should I do?</span></font></div>
<div><font color="#0000ff">1. 15% <
cpu_util < 30%, scaling_in 1
instance with 300s cooldown time<br>
2. cpu_util < 15%, scaling_in 2
instances with 600s cooldown time</font></div>
</div>
</div>
</blockquote>
</div>
</blockquote>
</span>
<div><span style="color:rgb(255,0,0)"><i> You can
define the cooldown by specifying it when creating
the policy or attaching it to a cluster. The
cooldown check logic will prevent a policy taking
effect if cooldown is still in progress.<br>
<a moz-do-not-send="true"
href="http://git.openstack.org/cgit/openstack/senlin/tree/senlin/engine/actions/base.py#n431"
target="_blank">http://git.openstack.org/cgit/openstack/senlin/tree/senlin/engine/actions/base.py#n431</a><br>
</i></span> </div>
<span class="">
<blockquote class="gmail_quote" style="margin:0px 0px
0px 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
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<div><font color="#0000ff"><br>
</font></div>
<div><font color="#0000ff">For a senlin
webhook, could we assign a policy which
will be checked ?</font></div>
</div>
</div>
</blockquote>
</div>
</blockquote>
</span>
<div> <i><span style="color:rgb(255,0,0)"> User is
not allowed to specify the policy when defining a
webhook. The webhook target is decided by target
object(cluster or node) and target action type.</span></i><br>
</div>
</div>
</div>
</div>
</div>
</div>
</blockquote>
<br>
<font face="\Microsoft YaHei UI\"> Yes we can define cooldown for
each policy, but <font face="\Microsoft YaHei UI\">my meaning</font>
is that each cluster_scaling_in action is only checked by <font
face="\Microsoft YaHei UI\">specified </font>scaling_policy
like OS::Heat::ScalingPolicy i<font face="\Microsoft YaHei UI\">n
heat.</font><br>
1） In heat<font face="\Microsoft YaHei UI\">, </font>we could
define two scaling_in actions(via define two
OS::Heat::ScalingPolicy polices ), each scaling_in action is
checked by one OS::Heat::ScalingPolicy, so each scaling_in
action's cooldown is only checked in one OS::Heat::ScalingPolicy.<br>
2）<font face="\Microsoft YaHei UI\">B</font>ut in senlin,
each scaling_in action will be checked by all attached
scaling_policies, so all scaling_polices' cooldown will be
checked.</font><font color="#3333ff"> <font color="#000000">How
does senlin support different cooldown time for each scaling_in
action?</font><br>
</font><br>
<blockquote
cite="mid:CAPnJsYCnBW=vznwuS_f1TO8QccLO93QLCGdrg=3FoNpZ4H0fzw@mail.gmail.com"
type="cite">
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rgb(204,204,204);padding-left:1ex">
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<div>
<div dir="ltr"><span>
<div><br>
Then each time alarm1 is triggered,
cluster will be scaled out with count 1
which means one new node will be created
and added to cluster. When alarm2 is
triggered, cluster will be scaled out
with count 2 that two new nodes will be
created and added to cluster.<br>
<br>
The question you asked is really
interesting and we did consider to
support this kind of requirement using a
'complex' ScalingPolicy which defined
both trigger(alarm), webhook and some
rules for scaling. But after some
discussion, we felt that maybe we should
let some high level service/enduser to
define this kind of 'POLICY' since it's
more like a workflow definition rather
than a description of the rule cluster
scaling. So currently, we only provide
atomic operation(e.g. webhook, 'simple'
ScalingPolicy) in Senlin while leaving
the work of combining these operations
to support a use case to
enduser/high-level service.<br>
<br>
Thanks a lot for throwing this
interesting question and I do agree that
we should make more discussion about it
to think whether we need to adjust our
policy design to support this kind of
scenario more smoothly.<br>
<br>
--</div>
<div>
<div>
<div>
<div>
<div>
<div>
<div>Best regards,
<div><br>
</div>
<div>Yanyan</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</span></div>
</div>
</blockquote>
</div>
</blockquote>
</span></div>
<span class="HOEnZb"><font color="#888888"><br>
<br clear="all">
</font></span><br>
</div>
</div>
</div>
-- <br>
<div class="gmail_signature">Best regards,
<div><br>
</div>
<div>Yanyan</div>
</div>
</div>
<br>
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<pre class="moz-signature" cols="72">--
Best regards,
Jun Xu</pre>
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