Azure Functions Kafka Extension: Missing useful information for AutoOffsetReset

[moloneyd-draeger]

Hi Azure Docs team,

The supported host.json settings for the Kafka Azure Function binding are listed here.

The configuration option AutoOffsetReset / auto.offset.reset has some missing critical information that may apply generally to other options. I would update the docs with this information and add a link to the extension readme where this information is also available. (https://github.com/Azure/azure-functions-kafka-extension#librdkafka-configuration

Based on my experience, there are two issues with how AutoOffsetReset is documented:

• The default value is different between librdkafka "largest" and the Azure Extension "Earliest".
  • This is extremely important for understanding the impact of deploying new Triggers which will read from existing topics on a kafka broker. If possible I would display this information in an "important" section with a background highlight.
• The difference in spelling for the enum configurations. librdkafka allows {smallest, earliest, beginning, largest, latest, end, error} while the Azure Extension allows {Earliest, Latest}. While the mapping between these options is clear from context, I was very confused when I received the error below as the documentation states the properties are "inherited from the Apache Kafka C/C++ client library", and I expected the strings to match!

  System.Private.CoreLib: Exception has been thrown by the target of an invocation. Microsoft.Extensions.Configuration.Binder: Failed to convert configuration value at 'AzureFunctionsJobHost:extensions:kafka:AutoOffsetReset' to type 'Confluent.Kafka.AutoOffsetReset'. System.ComponentModel.TypeConverter: largest is not a valid value for AutoOffsetReset. System.Private.CoreLib: Requested value 'largest' was not found.

I think future developers and users would benefit from clarifying the above points in the docs. Thanks!

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• ID: f980975b-480d-664a-a564-348b255e0d47
• Version Independent ID: aeccfb49-062a-4bf5-21c8-f0e71bd9eaad
• Content: Apache Kafka bindings for Azure Functions
• Content Source: articles/azure-functions/functions-bindings-kafka.md
• Service: azure-functions
• GitHub Login: @ggailey777
• Microsoft Alias: glenga

[AjayBathini-MSFT]

@moloneyd-draeger Thanks for your feedback! We will investigate and update as appropriate.