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From Rohit Yadav <>
Subject RE: Metrics UI - Incorrect metrics data for zone/cluster
Date Thu, 12 May 2016 06:13:30 GMT

Originally, the feature was implemented using all the available list APIs in future we may
have a backend metrics API instead of aggregation in the UI/client side (done right now).
This feature assumes that no single cluster would have 500 hosts (also not supported by many
hypervisors to have 500+ hosts in a single cluster), the calculations are done for each cluster
in the cluster metrics view; similarly in zones metrics view calculations are done looping
through clusters per zone.

Feel free to assign the issue to me, I'll get back to you later.



Rohit Yadav
53 Chandos Place, Covent Garden, London  WC2N 4HSUK

-----Original Message-----
From: Rashmi Dixit [] 
Sent: Thursday, May 12, 2016 10:12 AM
Subject: Metrics UI - Incorrect metrics data for zone/cluster


I came across an issue in the metrics for zone and cluster. I have logged a bug for the same.

To quickly summarize the issue: APIs have a pagesize restriction - the global
setting is used as the max result count - value is typically 500. In this case, listClusters
and listHosts APIS are used to gather metrics data for zone and clusters. If there are 600
hosts, then one call to listHosts will only return 500 hosts. The usage data is summed up
for 500 hosts, however average is calculated based the total hosts which is 600.

To correct this, UI should fetch ALL hosts for ALL clusters to get the right result. Ideally
this kind of calculation should be done at the API level - large number of hosts will result
in performance degradation. The right way to fix this would be to add a new API for metrics
calculations at zones/cluster level.

@Rohit, since you are the original contributor, can you help me with the background on this?
Any comments/suggestions on doing this differently are most welcome.


Rashmi Dixit
Principal Product Engineer | CloudPlatform |

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