Does 'free' really mean 'busy'?

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09-18-2018 11:35 AM
deactivated-user-ChrisBeaudett
New Contributor III

We're evaluating ArcGIS Monitor and from the settings and reports the use of 'Max Free', 'Min Free' and 'BusyInstancesMax' is confusing.

The documentation says that "when Max Free and Max Instances are equal, you should consider increasing the number of instances on the service".  And in fact the reports flag those case where Max Free and MaxInstances are equal. That makes it seem like Max Free = the Max # of busy instances for the service, i.e. "busy" instances and not "free" instances. If that's the case, what does "Min Free" mean? To make it more confusing, when the condition is met and flagged in the reports, the Comments say "Warning: Max instances too low (Busy or Free equal Max). If available memory, increase min and max instances."  Why would Free = Max be a warning condition of "business"??

What's more, 'BusyInstancesMax' is documented as the "Total maximum number of ArcGIS Server busy instances in the report time period".  To me that means the number of times a service has maxed out its instances for the reporting period.  If that's the case then by its own reckoning, I would expect that when Max Free = MaxInstances then BusyInstancesMax should be non-zero, but that's not what I'm seeing in the reports:  some of those that are flagged are non-zero but some are zero as well.

What I"m trying to get to the bottom of is, how do I detect when the number of instances for a given service should be considered a candidate for increase?  It seems like it's simply those that are flagged in the report with "Warning: Max instances too low (Busy or Free equal Max). If available memory, increase min and max instances", but at the same time I'm seeing 0's for BusyInstancesMax.

Can anyone shed clarification around this?

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AndrewSakowicz
Esri Contributor

The logic behind this “free=max” is that ArcGIS Monitor collects ArcGIS Server stats every 5 or 15 min.  If at exactly the collection time,  busy=max,  we detect this intuitive condition.  But chances of that is only if this busy=max last for a long time.  In many cases, this demand is for a short time.  More likely condition is when busy=max does not happened when ArcGIS Monitor collects.  If there is no more requests for this service, these “busy” instances become free instances for the next 180 seconds (if kept default). And this condition is much more probably for us to catch.

Check this by correlating with increased ArcGIS Server throughput charts.  And if you monitor http, you should see corresponding increased response time as these requests are waiting for free instances.

 

Please consider increasing instances as recommend by ArcGIS Monitor.  The manual adjustment of instances are practical only if dealing with a handful of services. But if have many services with variable usage, you should consider ArcSOC Optimizer from https://arcgismonitor.maps.arcgis.com/home/gallery.  It will detect these conditions and make appropriate adjustments automatically daily.

 

I hope this clarifies it.

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3 Replies
AndrewSakowicz
Esri Contributor

The logic behind this “free=max” is that ArcGIS Monitor collects ArcGIS Server stats every 5 or 15 min.  If at exactly the collection time,  busy=max,  we detect this intuitive condition.  But chances of that is only if this busy=max last for a long time.  In many cases, this demand is for a short time.  More likely condition is when busy=max does not happened when ArcGIS Monitor collects.  If there is no more requests for this service, these “busy” instances become free instances for the next 180 seconds (if kept default). And this condition is much more probably for us to catch.

Check this by correlating with increased ArcGIS Server throughput charts.  And if you monitor http, you should see corresponding increased response time as these requests are waiting for free instances.

 

Please consider increasing instances as recommend by ArcGIS Monitor.  The manual adjustment of instances are practical only if dealing with a handful of services. But if have many services with variable usage, you should consider ArcSOC Optimizer from https://arcgismonitor.maps.arcgis.com/home/gallery.  It will detect these conditions and make appropriate adjustments automatically daily.

 

I hope this clarifies it.

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DavidColey
Frequent Contributor

Andrew - does the ArcSOC Optimizer available here:

https://www.arcgis.com/home/item.html?id=a0c2dde661f14b8ca58b8b7b5ddeb379 

work for ArcGIS Monitor 10.7 ?

Thanks,

David

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ShreeRajagopalan
Esri Contributor

Yes, it does.