aspnetcore-serilog-azureappservice

Simple ASP.NET Core Web API using Serilog to log to Azure Application Insights and App Service Log Stream

Logging

The .NET Core Web API in this repository uses ILogger of NuGet package Microsoft.Extensions.Logging. ILogger<T> is injected into the constructor of the class that needs to log. The underlying logging framework is Serilog. Serilog is configured in Program.cs and appsettings.json (appsettings.Development.json for local development environment) of the application.

Serilog is configured so that the application logs to the following sinks:

• Startup logs are logged to the console
• Any other application logs are logged ...
  • ... to the console, if the application runs in local development environment (i.e. when started in Visual Studio or Visual Studio Code where ASPNETCORE_ENVIRONMENT is by default set to Development)
  • ... to Azure Application Insights, if the the application runs in Azure on an Azure App Service (where ASPNETCORE_ENVIRONMENT is by default set to Production, therefore appsettings.Development.json is ignored)
  • ... to a log file, if the application runs in Azure on an Azure App Service to allow viewing near-realtime logs in Azure App Service Log stream

Important

In this sample Serilog is configured for Linux Azure App Services

Serilog creates traces in Application Insights (TraceTelemetry) for log levels defined in appsettings.json MinimumLevel. However, if the log event contains any exceptions it will always be sent as ExceptionTelemetry to Application Insights. To make Serilog sending custom application logs of log level Debug to Application Insights, the following application setting has to be added to the Azure App Service (see Settings > Configuration of App Service):

• Name: Serilog__MinimumLevel__Default
• Value: Debug

Important

This setting should only be added to the Azure App Service in case of troubleshooting. Otherwise, the logs will be flooded with debug logs.

Azure Application Insights

To query the application logs in Azure Application Insights, proceed as follows:

1. Log in to the Azure Portal
2. Switch to the corresponding directory (Azure tenant)
3. Search for Application Insights in the search bar on the top
4. Select the application insights resource the app sends its logs to
5. Navigate to Logs in section Monitoring in the menu on the left
6. Enter one of the following queries in the query editor and click Run:
   • To query non exception logs

     traces
     | where message startswith "START_OF_LOG_MESSAGE"
     

   • To query exception logs

     exceptions
     

Stream logs

Important

Make sure you check the whole stream for your logs as they seem to not be ordered by date but by log file

To stream the application logs in near-realtime, proceed as follows:

1. Log in to the Azure Portal
2. Switch to the corresponding directory (Azure tenant)
3. Search for App Service in the search bar on the top
4. Select the app service resource the app runs on
5. Navigate to Log stream in section Monitoring in the menu on the left

Deployment to Azure

Prerequisites

• Azure tenant
• Azure subscription

Step by Step Manual

1. Create a new resource group (i.e. aspnetcore-serilog-azureappservice)

2. Create a new workspace-based application insights resource in the before created resource group (i.e. aspnetcore-serilog-azureappservice-appinsights)

3. Create a new app service plan in the before created resource group (i.e. aspnetcore-serilog-azureappservice-appplan)

   • Operating system: Linux
   • Pricing tier: F1

4. Create a new web app (i.e. aspnetcore-serilog-azureappservice-app)

   • Publish: Code
   • Runtime stack: .NET 8 (LTS)
   • Operating system: Linux
   • Linux Plan: select before created app service plan
   • Enable and configure continuous deployment under Deployment tab

5. Ensure the following application setting is set in the Azure App Service:

   This setting is already set, if deployment is done using GitHub Actions integration.

   • Name: APPLICATIONINSIGHTS_CONNECTION_STRING
   • Value: connection string of the before created application insights resource

Important

Without this setting, the application will not log to Application Insights.

After successful deployment, the weather forecast API endpoint is available under APP_SERVICE_DEFAULT_DOMAIN/WeatherForecast

Screenshots

Console logs

Azure Application Insights

Azure App Service Log Stream

Links

• Serilog
• https://learn.microsoft.com/en-us/azure/app-service/troubleshoot-diagnostic-logs