Functions Request Body Limit - App setting not working

hawthorne91 230

Hello, currently I have an API that takes in POST requests containing files, and uploads them to my Azure Blob Storage account. The issue is that when the files are bigger than 100MB, then the files do not upload.

I am aware that by default the limit to a request is 100MB. I found this post (https://zcusa.951200.xyz/en-us/answers/questions/1846216/confused-http-request-size-limit-of-100-mb-for-azu) stating that you can increase the limit of the request size by configuring the Functions_Request_Body_Size_Limit in the app settings, however when I set this value in my app settings to higher than 100MB, it still does not allow me to upload the file. For reference, the file I am trying to upload is around 101MB, and my function app is Consumption-based. Can anyone provide me guidance on how to proceed? Thank you.

Update: I upgraded to the Function Premium Plan type, however it still isn't working.

1 answer

Khadeer Ali 1,400 Reputation points Microsoft Vendor

2024-12-19T23:41:27.15+00:00

@hawthorne91

Welcome to the Microsoft Q&A Platform!

Thank you for reaching out about your file upload scenario. We understand this can be frustrating. While Azure Functions are great for many tasks, they're not ideally suited for very large file uploads (especially those over 100MB). This is due to limitations in request size, memory usage, and potential timeouts. Even adjusting settings like FUNCTIONS_REQUEST_BODY_SIZE_LIMIT doesn't fully resolve these challenges for larger files.

Given these challenges, could you try alternative solutions which is already mentioned in the thread you have gone through such as Azure Blob Storage direct uploads, which are specifically designed for managing large files efficiently or Chunked Uploads, Break the file into smaller chunks (e.g., <100MB) and upload them sequentially or in parallel. The Function can reassemble the chunks in Blob Storage.

If this answers your query, do click Accept Answer and Yes for was this answer helpful. And, if you have any further query do let us know.
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hawthorne91 230 Reputation points

2024-12-20T14:02:18.2533333+00:00

Hi @Khadeer Ali thank you for the response! I appreciate the detailed explanation and the suggested alternatives. I was just curious, though— is there any way to increase the request size limit beyond 100MB directly within the existing Azure Function setup?

The reason I ask is that this is a portion of an existing API that external users are already actively using, and altering the architecture (e.g., implementing direct uploads or chunking) would significantly impact the current implementation. I’d like to explore all possible ways to maintain the current structure before considering changes to the architecture.

Thank you again for your help!

hawthorne91 230 Reputation points

2024-12-20T14:32:28.95+00:00

Hi @Khadeer Ali thank you for your response!

Is there any way to increase the request size beyond 100MB directly within the existing Azure Function setup?

The reason that I ask is that this is a portion of an existing API that external users are already actively using, and altering the architecture would significantly impact the current implementation. I'd like to explore all possible ways to maintain the current structure before considering changes to the architecture.

Users submit their files through an HTML page, and then this page sends a fetch request to the Azure Function to upload the file so I was considering breaking down the file on the HTML end and then on the Azure Function end reassemble the file. Thoughts?

Khadeer Ali 1,400 Reputation points Microsoft Vendor

2024-12-20T17:31:59.76+00:00

hawthorne91,

Thank you for your follow-up. I understand the need to explore all possibilities to maintain the current API structure, especially given its active usage by external users.

Your idea of breaking down the file on the client-side and reassembling it in the Function App could be a practical approach which might work.

I think we can achieve this by client-side chunking by using JavaScript on the HTML page to split the file into smaller chunks and upload them sequentially or in parallel via multiple fetch requests.

In the Azure Function, receive the chunks, store them temporarily and reassemble them once all parts are uploaded.

hawthorne91 230 Reputation points

2024-12-20T17:48:22.0033333+00:00

Got it, thank you, Khadeer Ali! I'll be sure to do just that.

One other issue though is that it seems like when I send my requests, I can't send smaller files? I am going to eventually implement the fix we talked about, however currently with the existing architecture I tried uploading a 92MB file and it didn't work, it just returns an error. For smaller files that I've tested though (9MB) they seem to work. Do you know why that may be the case?

hawthorne91 230 Reputation points

2024-12-20T19:11:17.06+00:00

Hi Khadeer Ali,

My apologies if my previous comment sent along with this one, my comment is not visible to me so I wanted to comment again just to make sure my comment goes through.

I am going to change the architecture to reflect what we've talked about, thank you! I wanted to ask you though, currently when I upload files I run into errors with files that are less than 100MB, and I was wondering how that could be explained? I uploaded a 92MB file and my API still returned an error.

Thank you!

Khadeer Ali 1,400 Reputation points Microsoft Vendor

2024-12-20T22:24:27.1266667+00:00

hawthorne91,

Try to increase the function's timeout setting in the host.json file for more control over execution time. But still Divide the file into smaller chunks might be around 4MB you have suggested earlier might be a better solution.
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