Can't change timeout for HttpClient when running Azure function app

Question

Can't change timeout for HttpClient when running Azure function app

Reid Moffat 0

I have a C# function app on azure that calls another API using the HttpClient class, but it keeps timing out and I can't find how to change the timeout time from the default (I think 100 seconds or 2 minutes?). The API endpoint I'm calling is expected to take a while, it's not an issue with the API as I've confirmed the api is working ok.

I've tried changing the Timeout property of HttpClient (tried half an hour and an hour) but this doesn't do anything. Stack overflow says the timeout is defined by the server, not the code, and you need to add a executionTimeout property to the Web.config to change the max timeout; however, this is a function app that doesn't have a Web.config and the executionTimout needs an xml entry in this file, not an environment variable.

How can I increase the HttpClient timeout time? Note that my function app (v2) isn't timing out, just specifically the call to another API that is and throws an exception.

MayankBargali-MSFT 70,936 Reputation points Moderator

2023-08-08T06:13:19.6466667+00:00

Hi @Reid Moffat

Following up to see if my answer helps. Feel free to get back to me if you need any assistance.

Please "Accept Answer" if the answer is helpful so that it can help others in the community.

2 answers

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MayankBargali-MSFT 70,936 Reputation points Moderator

2023-08-08T06:13:19.6466667+00:00

Hi @Reid Moffat

Following up to see if my answer helps. Feel free to get back to me if you need any assistance.

Please "Accept Answer" if the answer is helpful so that it can help others in the community.

Answer 1

Bruce (SqlWork.com) 77,686 Volunteer Moderator

azure functions have a limited cpu and runtime. you can not extend this. you can switch hosting technology or better design the system

you could change your api to return a unique id right away, and do web hook callback with the id when done. this web hook can then complete the transaction call, or call another azure function.

you could also do polling for completion, if api can not call web hooks

Reid Moffat 0 Reputation points

2023-08-04T20:59:33.69+00:00

<see below>
Reid Moffat 0 Reputation points

2023-08-04T21:26:13.1166667+00:00

I'm not trying to extend the function app execution time, I'm just trying to extend the HttpClient api call timeout time. Even after the API call times out, my function app still runs a bunch of code for a little bit and successfully handles the response without timing out.

If I found some way to extend the HttpClient timeout time for a long time like 2 hours for example then yes of course the function app would time out, but the default timeout is so short that I can at least double or triple it before the function app starts to timeout. E.g. I think my api call will take around 3 minutes, so even if function apps timeout after 5 minutes I'd still be good
Bruce (SqlWork.com) 77,686 Reputation points Volunteer Moderator

2023-08-08T16:01:47.5266667+00:00

as noted below, the azure function's HttpClient outgoing requests go thru a load balancer. you can not increase the load balancer timeout.

Answer 2

MayankBargali-MSFT 70,936 Moderator

@Reid Moffat Thanks for reaching out and sharing more details.

If a function that uses the HTTP trigger doesn't complete within 230 seconds, the Azure Load Balancer will time out and return an HTTP 502 error. The function will continue running but will be unable to return an HTTP response. For long-running functions, we recommend that you follow async patterns and return a location where you can ping the status of the request. For information about how long a function can run, see Scale and hosting - Consumption plan.

The same is documented here

Let me know if you have any queries or concerns.

Reid Moffat 0 Reputation points

2023-08-08T12:47:20.9066667+00:00

My function app does not time out, I'm not trying to extend my function app timeout time. I'm trying to extend the time before HttpClient throws a 500 timeout error within the function app context.

Currently, HttpClient times out far before the 230 seconds - if I was able to double this timeout time, I could run my API fine and still wouldn't time out my function app within the 230 seconds since HttpClient times out so quickly.
MayankBargali-MSFT 70,936 Reputation points Moderator

2023-08-09T12:25:52.1966667+00:00

@Reid Moffat Thanks for your response. It depends on whether your external API call supports the query timeout parameter or any other way to set the API. There is nothing to do with the azure runtime environment. Your external endpoint should support it as it might be getting timeout. To troubleshoot this issue further I will suggest you to run your external endpoint outside function environment and check if you are getting the response correctly and if it is getting timeout. If you are running in the windows OS, then your leverage kudo and hit your endpoint directly as it may be communication issue with function and your external endpoint in case if you are able to get the proper response from your API outside azure environment. There is already previous discussion on a similar issue where the external endpoint was getting timeout with 21 seconds.
Reid Moffat 0 Reputation points

2023-08-11T02:40:55.51+00:00

@MayankBargali-MSFT I checked the other API I'm calling (the one that times out, it's a Java API on Azure also) and the timeout for it is set at 10 minutes in the Web.config. When running the same code in an API context (running my C# API locally), this Httpclient request goes for longer (230 seconds) before timing out instead of 100 seconds in the function app.

Some good news though; I was able to bypass the 100-second limit of HttpClient timeout in function apps by using this guide here: https://thomaslevesque.com/2018/02/25/better-timeout-handling-with-httpclient/, however, the timeout limit was capped at 230 seconds and I couldn't go longer than that.

Also, my function apps themselves don't seem to timeout - I used Thread.Sleep() for almost 4 hours in a function app and it still didn't timeout so the function app is ok:

So it appears 230 seconds is the limit for API endpoints on azure, and this is likely caused by the API I'm calling (not HttpClient since I can bypass the 100 second limit) since the API is on Azure too. If there is any way around this, please let me know, otherwise, I do have 130 more seconds now so I can try to figure out a workaround.
MayankBargali-MSFT 70,936 Reputation points Moderator

2023-08-11T09:47:22.1+00:00

@Reid Moffat The function should timeout max 10 minutes if it is consumption tier and for premium max 60 minute as the limit you have configured. I will suggest to open a support ticket with us to review this behavior further. If you don't have the support plan, then please send an email to “Attn:Mayank” to AzCommunity[at]Microsoft[dot]com referencing this thread so we can enable one time support request on your subscription.

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Can't change timeout for HttpClient when running Azure function app

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