Azure Functions does not support DiagnosticListener callbacks when using System.Diagnostics.DiagnosticSource (> 4.7.0)

[utpilla]

DiagnosticListener callbacks are not called in Function apps when using System.Diagnostics.DiagnoticSource (> 4.7.0)

Investigative information

Tried this locally

Repro steps

• Clone this repo: https://github.com/utpilla/AzureFunctions-DiagnosticSource/tree/DiagnosticSource_5.0.1 and switch to branch DiagnosticSource_5.0.1
• Run the AzureFunctions-DiagnosticSource project
• Make an HTTP GET request to http://localhost:7071/api/HttpHandlerDiagnosticListener

Expected behavior

Response should be:

[
    "System.Net.Http.HttpRequestOut.Start",
    "System.Net.Http.Request",
    "System.Net.Http.HttpRequestOut.Stop",
    "System.Net.Http.Response"
]

This is a list of events that are logged by HttpClient when making an outbound Http request

Actual behavior

Response is empty

Known workarounds

Revert the System.Diagnostics.DiagnosticSource package version to 4.7.0

Related information

• It works correctly with the main branch as it's using System.Diagnostics.DiagnosticSource (= 4.7.0)
• Programming language used: C#
• Links to source: https://github.com/utpilla/AzureFunctions-DiagnosticSource/tree/main

[fabiocav]

We need to track the unification change in 4.0.

Tagging @brettsam for validation in v4

[RohitRanjanMS]

@utpilla this is working in V4, we can close this issue.
@brettsam @fabiocav FYI

[ThomsonTan]

Haven't seen any PR tagged for this issue. Is it working now?

[RohitRanjanMS]

Hi @ThomsonTan did this not work for you in V4?

[cijothomas]

Hi @ThomsonTan did this not work for you in V4?

It should work in V4 and Otel 1.3.*.
A working app is here: https://github.com/cijothomas/FunctionsOpenTelemetry/tree/master/FunctionsOpenTelemetry

[agr]

Should it work with non-isolated workers? What I see is that msbuild when building a function deletes the "System.Diagnostics.DiagnoticSource.dll" file (presumably by a RemoveRuntimeDependencies msbuild task) if it ends up in the output directory, then when the code touches any OpenTelemetry class a TypeInitializationException exception is thrown:

FileNotFoundException: Could not load file or assembly 'System.Diagnostics.DiagnosticSource, Version=7.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'. The system cannot find the file specified.

OpenTelemetry.Api/1.4.0 depends on that particular version of System.Diagnostics.DiagnosticSource.

Setting _FunctionsSkipCleanOutput to true (as suggested here) seem to help though.

[fabiocav]

@agr 7.0.0 dependencies will not work in Azure Functions 4.0 (in-proc) with the unification rules it has.

If you need to use 7.0.0, the recommendation is to use the Isolated (out-of-proc) model.

[fabiocav]

Closing this as resolved