Azure Functions - misc

• FunctionsStartup
• Upgrade from V2 to V3
• CORS
• Local dev - Error: “The UTC time represented… between year 0 and 10,000”
• Disable a function
• Locked dll files during deploy
• Application Insights custom data (CustomMetrics)
• Hosting

FunctionsStartup

Steps:

• Add reference to:
  • Microsoft.Azure.Functions.Extensions
  • Microsoft.NET.Sdk.Functions >= 1.0.28
• Create a Startup class, extending FunctionsStartup and overriding Configure method
• Mark the assembly with FunctionsStartup attribute

using Microsoft.Azure.Functions.Extensions.DependencyInjection;

[assembly: FunctionsStartup(typeof(BasicFunctions.Startup))]

namespace BasicFunctions
{
    public class Startup : FunctionsStartup
    {
        public override void Configure(IFunctionsHostBuilder builder)
        {
            // code...
        }
    }
}

Details: https://docs.microsoft.com/en-us/azure/azure-functions/functions-dotnet-dependency-injection

Upgrade from V2 to V3

In Visual Studio, update version and references inside project file.

From:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netcoreapp2.1</TargetFramework>
    <AzureFunctionsVersion>v2</AzureFunctionsVersion>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.NET.Sdk.Functions" Version="1.0.38" />
  </ItemGroup>

To:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netcoreapp3.1</TargetFramework>
    <AzureFunctionsVersion>v3</AzureFunctionsVersion>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.NET.Sdk.Functions" Version="3.0.11" />
  </ItemGroup>

When you deploy from Visual Studio, a warning appears. Click “yes”.

Verify that FUNCTIONS_EXTENSION_VERSIONS is correctly set.

Verify that current runtime version is V3:

CORS

In local.settings.json

  "Host": {
    "CORS": "*"
  }

Local dev - Error: “The UTC time represented… between year 0 and 10,000”

The listener for function XXXXXXXXXX  was unable to start. 
System.Private.CoreLib: The UTC time represented when the offset
is applied must be between year 0 and 10,000. (Parameter 'offset')

Cause: something went wrong inside Azurite.

Solution: stop Function and delete blob folder containig the timers information. E.g. /azure-webjobs-hosts/timers/hostname-1289032772/ To identify the correct folder, check the Azurite logs when App Function is starting.

Disable a function

Add a configuration key in the format

"AzureWebJobs.[function_name].Disabled": "true"

It works both in local.settings.json (visual studio) and on Azure.
Ref: https://docs.microsoft.com/en-us/azure/azure-functions/disable-function

Locked dll files during deploy

In configuration, add key MSDEPLOY_RENAME_LOCKED_FILES = 1

Application Insights custom data (CustomMetrics)

Azure Functions automatically sends data to Application Insights if APPINSIGHTS_INSTRUMENTATIONKEY is present. To manually use TelemetryClient from code, e.g. for sending custom Trace or Metric, it’s required to add a reference to App Insight Nuget packages.
Do not add “low-level” packages directly but, instead, add only Microsoft.Azure.WebJobs.Logging.ApplicationInsights It will bring all required packages in a compatible way to the hosting environment. More details here: https://github.com/MicrosoftDocs/azure-docs/issues/35181#issuecomment-512288993
If Nuget packages are not compatible OR the key APPINSIGHTS_INSTRUMENTATIONKEY is missing, you’ll get errors like:

Microsoft.Extensions.DependencyInjection.Abstractions: Unable to resolve service  
for type 'Microsoft.ApplicationInsights.Extensibility.TelemetryConfiguration'   
while attempting to activate 'BasicFunctions.CustomMetrics'

More information about App Insights in Functions:

• https://docs.microsoft.com/en-us/azure/azure-monitor/app/azure-functions-supported-features (a bit outdated)
• https://docs.microsoft.com/en-us/azure/azure-functions/functions-monitoring#log-custom-telemetry-in-c-functions

Note: functions must be declared as not static and a constructor is required to get the pre-configured TelemetryClient.

Hosting

https://github.com/Azure/azure-functions-host/