Can I Purchase a Reserved Instance of App Service that Auto Scales up and down on a schedule

Jim Derry 101

We have an App Service that needs more capability for about 12 hours in the workdays, and less during offpeak times and the weekend. I would like to purchase a reserved instance of P2V3 for use during my peak periods, and then auto-scale it down on a schedule during off peaks.

This would help me provide a lot better service and save me some money in the process.

How can I make this happen?

Accepted answer

Grmacjon-MSFT 16,011 Reputation points

2023-02-08T17:54:38.63+00:00

Hi @Jim Derry , You can use Azure Autoscaling to automatically scale your App Service based on a schedule or metrics. You can set up different autoscale profiles for different times of the day or week, and configure rules to scale up or down based on the metrics you choose.

For example, you can create a profile for your peak periods, where you set the minimum number of instances to 1 and the maximum to 2. Then, you can create a schedule that runs this profile during your peak hours.

During off-peak times, you can create another profile with a lower minimum and maximum number of instances, and set a schedule for this profile to run during off-peak hours.

You can also configure rules to scale up or down based on metrics such as CPU usage or memory usage. This way, your App Service will automatically scale up or down based on the current load.

Hope that helps. Please let us know if you have further questions

-Grace
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Jim Derry 101 Reputation points

2023-02-08T18:33:04.8766667+00:00

Hi Grace (@Grmacjon-MSFT ), thanks for your reply and willingness to help me out. That makes sense to me, but it will make more once I go through it.

My question to your reply is, how does this work with reserved instances? For example, would the Reserved Instance benefit work if I set up a reserved instance of a P1V3, and scaled out when it got busy to two P1V3s?

thanks,

Jim
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2 additional answers

TP 75,656 Reputation points

2023-02-08T18:09:44.48+00:00

Hi,

Unfortunately you cannot purchase a partial reservation. For example, if you purchase a three year reservation for App Service Premium v3 P2V3 it is valid for 24 hours a day, 7 days a week during the term. If you don't use it 12 hours of a day you would be wasting money during that time (unless you used it for a different app service).

What you could do is have a script that scales up your App Service for the peak periods during the work week, and then scales it down during off peak and weekends. You would pay full price, but would save money since a lower-price plan would be used during off peak.

If you had multiple app service plans with non-overlapping peak times purchasing a reservation could save money. For example, say you had two app service plans. The first one had peak time of 9am to 9pm and the second one had peak time of 9pm to 9am. Your script would scale the plans so that only one of them is using the reservation at a time resulting in little to no waste of the reservation.

It is best to crunch the numbers for your precise scenario to determine if buying a reservation will save you money or not. Sometimes it is cheaper to buy reservation while other times it is cheaper to pay full price and scale up/down as needed.

If the above is helpful please click Accept Answer.

Thanks.

-TP
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TP 75,656 Reputation points

2023-02-08T18:30:19.55+00:00

@Jim Derry Please note I'm referring to scale up/down, which is changing the app service plan. This is different than scale out/in, which is adding/subtracting number of running instances. This is another example where number crunching is called for, because it may cost more/less to have a reservation and scale to more instances during peak time (and pay full price for additional instances).

Jim Derry 101 Reputation points

2023-02-08T18:39:49.2966667+00:00

Thanks for your reply, TP (I couldn't get your name to work). I appreciate you being right up front with the bottom line.

I see what you mean about crunching the numbers. there doesn't seem to be a clear cut, use this method, approach.

If I used the scale-up and scale-down approach for different App Service Plans, do the App Service Plans need to be in the same family? For example, If I purchased a P2V3 to run for 12 hours per day and pay full price, could I also use a Standard S1 plan to run during the off-duty hours? Would these two plans wor together to support the app as long as they run at different times?

Thanks,

Jim

TP 75,656 Reputation points

2023-02-08T19:41:37.3633333+00:00

Hi Jim,

If you purchase a P2V3 reservation then you want to make certain you have a running P2V3 App Service plan 24x7 (or as close to that as possible) or else you lose money. The reservation discount will only be applied if there is an active matching App Service plan (P2V3) to apply it to.

Another way to think of it is you are buying a coupon book. In this book, you have separate coupons for each hour that provide you 1 free hour of P2V3 App Service plan, 1 instance, for the entire 3 years. Each coupon is only valid for a specific hour on a specific date during the three years. For example, if the time is 11am on February 9, 2023 you can use the coupon marked "2023-02-09 10:00-11:00am" to cover the cost of the previous hour's usage. In the billing details it would actually show cost as $0.

If you didn't have a P2V3 App Service plan running during 10-11am then that coupon was wasted, and since you paid money for the coupon you wasted money. The granularity is smaller than 1 hour but I used 1 hour to simplify.

As a side note you cannot purchase a reservation for Standard S1 plan.

Does the above make sense? It's "use it or lose it". Like having mobile data that doesn't carry over.

Jim Derry 101 Reputation points

2023-02-09T17:07:28.42+00:00

Hi TP,

Thanks for your analogy, I understand coupon books and have been crunching some numbers. Is it feasible for me to purchase a reserved instance of P1V3 and set it to autoscale out to a second instance when demand requires it? that would give me the best coverage if the second instance can spin up fast enough.

If I could purchase a reserved instance in this scenario, how would the second P1V3 instance be priced? At the reserved rate or the pay-as-you-go rate?

Will two P1V3 be as efficient as a single P2V3?

Thanks,

jim

TP 75,656 Reputation points

2023-02-09T17:27:43.0166667+00:00

Hi Jim,

Don't buy reserved instance (of any size) before you test your intended configuration. For example, start out with P1V3 set to auto scale out to 2 instances and run it for 1-2 months, monitoring performance. During this test phase you will pay full pay-as-you-go price for all usage.

Once you are satisfied that the configuration performs well and will likely meet your needs for the duration of the reservation, only then do you purchase a reserved instance. It might be that buying one P1V3 reserved instance is the best option, but you need to test.

If you purchase one P1V3 the first instance that is running 24x7 would be at the discount reserved price (would show as 0 since you are essentially prepaying) and then the second instance would be billed at pay-as-you-go rate.

In regards to your question as to if two P1V3 will be as efficient as single P2V3, this depends on your application and workload. Testing and/or detailed knowledge of the specific application is required to find the answer.

TP 75,656 Reputation points

2023-02-09T17:27:43.7833333+00:00

Hi Jim,

Don't buy reserved instance (of any size) before you test your intended configuration. For example, start out with P1V3 set to auto scale out to 2 instances and run it for 1-2 months, monitoring performance. During this test phase you will pay full pay-as-you-go price for all usage.

Once you are satisfied that the configuration performs well and will likely meet your needs for the duration of the reservation, only then do you purchase a reserved instance. It might be that buying one P1V3 reserved instance is the best option, but you need to test.

If you purchase one P1V3 the first instance that is running 24x7 would be at the discount reserved price (would show as 0 since you are essentially prepaying) and then the second instance would be billed at pay-as-you-go rate.

In regards to your question as to if two P1V3 will be as efficient as single P2V3, this depends on your application and workload. Testing and/or detailed knowledge of the specific application is required to find the answer.

TP 75,656 Reputation points

2023-02-09T17:27:45.36+00:00

Hi Jim,

Don't buy reserved instance (of any size) before you test your intended configuration. For example, start out with P1V3 set to auto scale out to 2 instances and run it for 1-2 months, monitoring performance. During this test phase you will pay full pay-as-you-go price for all usage.

Once you are satisfied that the configuration performs well and will likely meet your needs for the duration of the reservation, only then do you purchase a reserved instance. It might be that buying one P1V3 reserved instance is the best option, but you need to test.

If you purchase one P1V3 the first instance that is running 24x7 would be at the discount reserved price (would show as 0 since you are essentially prepaying) and then the second instance would be billed at pay-as-you-go rate.

In regards to your question as to if two P1V3 will be as efficient as single P2V3, this depends on your application and workload. Testing and/or detailed knowledge of the specific application is required to find the answer.
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Jim Derry 101 Reputation points

2023-02-10T13:07:12.4466667+00:00

Thanks, TP. We have been testing the P1V3 for over two months already. It doubles our current capacity and a reserved instance will cost us the same as a P2V2. But we're growing and need a way to easily grow our capabilities as they are needed.

After testing, number crunching, and this discussion (thanks to you and @Grmacjon-MSFT ); it seems like the simplest option for me is to purchase the reserved instance on P1V3, and then scale out to multiple instances as needed.

The only other option that will give me that V3 power is to scale between a P1V3 at full price and a Standard S1 during off-peak hours. But that adds complexity and I don't think Azure will let me scale between an S1 and a P1V3. am I wrong in that understanding of the scaling?
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TP 75,656 Reputation points

2023-02-13T14:31:08.2766667+00:00

Hi Jim. As I mentioned above, to scale up from S1 to higher plan and back down you can use a script and set it to run on a schedule. It is not difficult to write since in its simplest form you are just running command to change the SKU. There is no built-in auto scale up/down capability like there is for auto scaling out/in.
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