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Service Bus and Functions, facing inconsistent processing and failures

Sujeeth Velutarala 20 Reputation points
2025-07-28T05:38:06.32+00:00

Hello all,

We are currently experiencing frequent and inconsistent success/failure rates in our system. Here's a high-level overview of our setup:

  • Messages are received via an API call (.NET 6.0, TLS 1.2).
  • These messages are then routed to an Azure Function (.NET 4.8, TLS 1.2).
  • Depending on the functionality, the messages are forwarded to a Service Bus (TLS 1.0).
  • An Azure Function listens to the Service Bus and picks up the messages for further processing.

In production, when we process around 150 records, approximately 120 succeed while the remaining fail. We're trying to understand the root cause of this inconsistency.
I suspect the issue is with deprecated TLS versions mismatch with functions and service bus. Also the frameworks are also outdated.

Could someone help me understand, if you have seen these kinds of issues? Is my understanding being right towards the issue.
Kindly help and throw some views on this.

Regards,

Sujeeth

Azure Service Bus
Azure Service Bus
An Azure service that provides cloud messaging as a service and hybrid integration.

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  1. Harish Badijana 15 Reputation points Microsoft External Staff Moderator
    2025-08-04T09:33:16.56+00:00

    @Sujeeth Velutarala I understand You're investigating inconsistent success/failure rates in your system, where approximately 120 out of 150 records succeed during processing. Your suspicion centers on TLS version mismatches and outdated frameworks across components like .NET 6.0 APIs, .NET 4.8 Azure Functions, and Service Bus using TLS 1.0.

    Based on Your setup involves:

    API calls via .NET 6.0 using TLS 1.2

    Azure Functions on .NET 4.8 also using TLS 1.2

    Azure Service Bus configured with TLS 1.0

    This configuration introduces a TLS downgrade risk, especially when newer clients (.NET 6.0) interact with older services (Service Bus on TLS 1.0). According to Use-approved-version-of-TLS-for-Azure-Service-Bus, even if a TLS 1.2 connection is initiated, the Service Bus may fall back to TLS 1.0 if not explicitly configured to reject older versions. This fallback can cause intermittent failures, especially under load or when retry logic is involved.

    To avoid these issues:

    Upgrade TLS on Service Bus

    Set the minimum TLS version to 1.2 using Azure CLI:

    az servicebus namespace update --name <your-namespace> --resource-group <your-rg> --min-tls-version 1.2

    This ensures all connections use TLS 1.2 or higher, eliminating fallback risks

    Upgrade Azure Functions

    Move from .NET 4.8 to .NET 6.0 or .NET 8.0 for better TLS handling and performance.

    Enable Diagnostic Logging

    Use Azure Monitor and Application Insights to trace TLS negotiation failures and identify patterns in failed requests.

    Review Retry Policies

    Ensure retry logic in your Azure Functions and Service Bus clients is configured to handle transient TLS errors gracefully.

    I hope this resolve the issue, Kinldy reach out to me for any further assistance

    1 person found this answer helpful.
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