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<p class="MsoNormal">Hi,<o:p></o:p></p>
<p class="MsoNormal">A design issue is observed in ceilometer service of Openstack. Setup include multiple compute nodes and 3 controller nodes. Meters from each compute node are sent to all the 3 ceilometer instances via RabbitMQ in round robin fashion at
an interval of 10 min. After transformation of cumulative cpu meter data, cpu_util is generated by ceilometer instance at controller node and is published to the http address configured in ceilometer pipeline configuration. cpu_util is used by the application
to take the decision if scaling of VM needs to be triggered or not.<o:p></o:p></p>
<p class="MsoNormal">Ceilometer instance calculates cpu_util for a VM from the difference between cumulative cpu usage of VM at two timestamp divided by the timestamp difference. Let’s say 1 compute node send the cumulative cpu usage of a VM (C1, C2, C3, C4)
at timestamp T1, T2, T3, T4 (difference between any two timestamp is 10 min). Now (C1,T1) & (C4,T4) tuple is received by ceilometer instance 1, (C2,T2) by instance 2, (C3,T3) by instance 3. Here even if CPU usage of VM is increased between T1 & T2, cpu_util
is calculated for 30 min duration (T1 & T4) rather than as expected for 10 min. This leads to scaling getting triggered after T4 that too when CPU usage is consistently above the threshold between T1 and T4.<o:p></o:p></p>
<p class="MsoNormal">Please suggest how could this issue could be resolved. Do we have any solution to bind VM or compute node meter data to specific ceilometer instance for processing?<o:p></o:p></p>
<p class="MsoNormal">Regards,<o:p></o:p></p>
<p class="MsoNormal">Arvind.<o:p></o:p></p>
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