chintanr11-MSFT avatar image
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chintanr11-MSFT asked chintanr11-MSFT commented

Azure Functions Premium Plan Pricing

I have an Azure Function Premium Plan with following configurations:

Maximum Burst: 20
Minimum Instances: 1

Always Ready Instances: 1
Enforce Scale Out Limit: No

I wanted to understand the granularity of price calculations in this case. I understood that the Functions App under Premium Plan is based on the number of warm instances, plus the additional amount of resource consumed during the execution (scale-out upto 20 instances) at Consumption Plan rates.

For instance, I have Python Durable Function running on Premium Plan (EP3) with Linux hosts. I am not able to capture, how to estimate the number of instances running per second, or memory consumed per second. The metric for Function Execution Units is blank or showing zero (0). The metric for Function Execution Count is not matching correctly with the number of calls initiated to the activity function.

Also, the price calculator, suggested here, is not helping us to find out the cost when the autoscale is enabled upto 20 instances (as shown above) and the instances will be added/removed based on the number of activity functions (or the load) - as it is rounding the time to nearest hour and also the additional instance count is getting fixed for that duration.

In my opinion, the estimates of resource consumption should be visible in metrics, like in Consumption plan. It should granularly capture the cost for the warmed instances and followed by the cost for the additional scale-out that occurred (if any, based on load).

UPDATE: In Consumption Plan, I am facing some of the scenarios, where the total function execution count is less than the expected count in the metrics blade in portal.

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JayaC-MSFT avatar image
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JayaC-MSFT answered chintanr11-MSFT commented
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Hi @JayaC-MSFT, based on following snippet in the pricing document link:

Azure Functions Premium plan provides enhanced performance and is billed on a per second basis based on the number of vCPU-s and GB-s your Premium Functions consume.

I am understanding that the Premium Plan cost can be computed if we know the resource consumption in terms of vCPU-s and GB-s - with per second granularity!

With the calculator links, it assumes that: (1) The function execution duration needs to be given rounded to integer hours. (2) The additional compute (which would get deployed apart from warm instances, during additional load) is consistent throughout the test - which would not be the case, as the autoscaler will keep adding or removing server based on the need of the load.

The metrics in Functions does not indicate exact resource consumption on a per second-basis. The metrics from the Plan are reported with "per minute granularity".

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