What is the impact of increasing Azure Application Gateway Timeout?

Question

Hi! I'm a newbie in supporting Azure services for a client. I would like to know if there is an impact in performance and pricing when increasing the Azure appgw timeout of our setup? Currently, we have a premium subscription and our gateway is configured with WAF V2 tier autoscale 0-10, and timeout is at default 20sec in prod (60s in staging). In the website, https://azure.microsoft.com/en-us/pricing/calculator/ , I can see that capacity unit (compute unit, connections, and throughput) are variables in computing monthly cost. Will this pricing computation be impacted by the change in timeout? How about the app gateway performance, and connection to APIM service?

The current average capacity of APIM is at 12% and maxing at 25%. While request is currently at around 200 per minute which is far from our current subscription 4000 per seconds.

Answer 1

@RodolfoMacaraeg-5593 Thank you for reaching out to Microsoft Q&A.

For v2: Application Gateway Pricing | Microsoft Azure (at the bottom of the page) - capacity unit is determined by how much traffic the gateway is processing (throughput, persistent connections, and compute unit). changing the request timeout value should not affect the cost as it wouldn't affect any of the three things that contribute to cost. However, this may effect the performance as the connections remain open for longer. Hope this helps.

Please let us know if you have any further questions and we will be glad to assist you further. Thank you!

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Answer 2

Hi @RodolfoMacaraeg-5593

The Keep-Alive timeout in the Application Gateway v1 SKU is 120 seconds and in the v2 SKU it's 75 seconds. The TCP idle timeout is a 4-minute default on the frontend virtual IP (VIP) of both v1 and v2 SKU of Application Gateway.
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