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Intermittent issue with Azure Bot Framework (with teams channel)– ServiceError "A task was canceled." with 502

Sweta Swami 0 Reputation points
2025-08-20T13:59:10.2866667+00:00

Hello Community,

I am facing an intermittent issue with my Azure Bot (built using Bot Framework) connected with the Teams channel. The bot usually works fine, but I have noticed this problem twice in the past two months.

While sending a message to the bot, I received the following error:

{"code":"ServiceError","message":"A task was canceled."}

Along with this, the request returned a 502 status code.

The strange part is that after about 3–4 minutes, the bot started working normally again without me making any changes.

Has anyone experienced this behavior before? I’d like to understand:

What might cause this kind of intermittent failure?

In what scenarios does this "A task was canceled" error typically occur?

Is it related to service downtime, networking issues, or bot channel latency?

How can I prevent or handle this more gracefully in my bot application?

Any guidance or insights would be greatly appreciated.

Thanks in advance!

Microsoft Teams | Development
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  1. Kudos-Ng 3,595 Reputation points Microsoft External Staff Moderator
    2025-08-20T14:48:08.8366667+00:00

    Hi Sweta Swami, 

    Thank you for posting your question in the Microsoft Q&A forum.  

    Based on the error message {"code":"ServiceError","message":"A task was canceled."} and the intermittent nature of the problem (along with the 502 status code), I did some research and would like to share a few insights: 

    • HTTP 502 typically indicates a server-side error, often due to a temporary issue with the backend service or infrastructure. Given that the bot resumed normal operation after a few minutes without any changes, this could point to a transient service downtime or network latency. 
    • The "A task was canceled" error is commonly associated with timeouts in asynchronous operations. This can happen if the bot’s response takes too long or if the HTTP client times out before receiving a response. 

    You can refer to this Stack Overflow post for more context on this error: c# - HttpClient - A task was cancelled? - Stack Overflow 

    Note: Microsoft is providing this information as a convenience to you. The sites are not controlled by Microsoft. Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please make sure that you completely understand the risk before retrieving any suggestions from the above link.

    Since this appears to be an intermittent issue, I recommend implementing a retry pattern in your bot logic when calling APIs or performing operations that may occasionally fail. This can help your bot recover gracefully from transient errors. You can also refer to this article for guidance on rate limiting and retry strategies in Teams bots: Rate limiting for bots - Teams | Microsoft Learn 

    If the issue becomes more frequent, consider checking the health of any dependent services or APIs your bot interacts with. 

    I hope the information above is helpful. If you have any further questions, please don’t hesitate to come back! 

    If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".      

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