Learn why the “HTTP Request Entity Too Large” error occurs when creating an Azure Function from Azure Stream Analytics. Understand how batch count and size mismatch leads to this issue and how to resolve it effectively.
Table of Contents
Question
You’re creating a function in Azure Function from Azure Stream Analytics, and receive the following exception from the function: “HTTP Request Entity Too Large.” Why did this happen?
A. You did not replace the Azure Cache for Redis primary connection string with your Azure Cache for Redis connection string.
B. The maximum batch count and size values used in the function are not consistent with the values entered in the Stream Analytics portal.
C. You did not replace your Azure Cache for Redis connection string with the Azure Cache for Redis primary connection string.
D. The maximum batch count and size values used in the function are equal with the values entered in the Stream Analytics portal.
Answer
When creating an Azure Function as an output for Azure Stream Analytics, the error “HTTP Request Entity Too Large” typically occurs due to inconsistent maximum batch count and size values between the Stream Analytics portal configuration and the Azure Function settings. This explanation corresponds to Option B: The maximum batch count and size values used in the function are not consistent with the values entered in the Stream Analytics portal.
B. The maximum batch count and size values used in the function are not consistent with the values entered in the Stream Analytics portal.
Explanation
Azure Stream Analytics uses batch processing to send data to Azure Functions via HTTP triggers. Two key properties—Max Batch Size (default: 256 KB) and Max Batch Count (default: 100 events)—control how data is batched before being sent to the function. If these values are mismatched between the Stream Analytics job configuration and the Azure Function settings, it can lead to oversized HTTP requests that exceed the allowed limit, triggering the “HTTP Request Entity Too Large” error.
Key Points
Batch Size Limit: The maximum size for each batch sent by Stream Analytics is configurable up to 256 KB by default. If the function’s HTTP trigger cannot handle this size, it results in an oversized request.
Batch Count Limit: The default batch count is 100 events per batch. If this exceeds what the function can process, it may also cause request issues.
HTTP Trigger Limits: By default, Azure Functions have a body size limit of 100 MB for HTTP requests, which can be adjusted using the FUNCTIONS_REQUEST_BODY_SIZE_LIMIT setting. However, exceeding this limit is not recommended due to performance implications.
Resolution Steps
To resolve this issue:
- Verify Batch Settings: Ensure that the Max Batch Size and Max Batch Count settings in your Stream Analytics job match what your Azure Function can handle.
- Adjust Function Configuration: If necessary, increase the HTTP request body size limit using the FUNCTIONS_REQUEST_BODY_SIZE_LIMIT setting in your Function App’s configuration.
- Consider Chunking or Blob Storage: For large data payloads, use chunking or store data in Azure Blob Storage instead of sending oversized batches directly via HTTP triggers.
By aligning these configurations, you can prevent oversized requests and ensure smooth communication between Azure Stream Analytics and your function.
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