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opentelemetry-dotnet/docs/logs/getting-started-console/README.md

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Getting Started with OpenTelemetry .NET Logs in 5 Minutes - Console Application

First, download and install the .NET SDK on your computer.

Create a new console application and run it:

dotnet new console --output getting-started
cd getting-started
dotnet run

You should see the following output:

Hello World!

Install the latest Microsoft.Extensions.Logging package:

dotnet add package Microsoft.Extensions.Logging

Install the OpenTelemetry.Exporter.Console package:

dotnet add package OpenTelemetry.Exporter.Console

Update the Program.cs file with the code from Program.cs.

Run the application again (using dotnet run) and you should see the log output on the console.

LogRecord.Timestamp:               2023-09-15T06:07:03.5502083Z
LogRecord.CategoryName:            Program
LogRecord.Severity:                Info
LogRecord.SeverityText:            Information
LogRecord.Body:                    Food `{name}` price changed to `{price}`.
LogRecord.Attributes (Key:Value):
    name: artichoke
    price: 9.99
    OriginalFormat (a.k.a Body): Food `{name}` price changed to `{price}`.
LogRecord.EventId:                 1
LogRecord.EventName:               FoodPriceChanged

...

LogRecord.Timestamp:               2023-09-15T06:07:03.5683511Z
LogRecord.CategoryName:            Program
LogRecord.Severity:                Fatal
LogRecord.SeverityText:            Critical
LogRecord.Body:                    A `{productType}` recall notice was published for `{brandName} {productDescription}` produced by `{companyName}` ({recallReasonDescription}).
LogRecord.Attributes (Key:Value):
    brandName: Contoso
    productDescription: Salads
    productType: Food & Beverages
    recallReasonDescription: due to a possible health risk from Listeria monocytogenes
    companyName: Contoso Fresh Vegetables, Inc.
    OriginalFormat (a.k.a Body): A `{productType}` recall notice was published for `{brandName} {productDescription}` produced by `{companyName}` ({recallReasonDescription}).
LogRecord.EventId:                 2
LogRecord.EventName:               FoodRecallNotice

...

Congratulations! You are now collecting logs using OpenTelemetry.

What does the above program do?

The program has a LoggerFactory with OpenTelemetry added as a LoggerProvider. This LoggerFactory is used to create an ILogger instance, which is then used to do the logging. Compile-time logging source generation is used to achieve structured logging and better performance. The logs are sent to the OpenTelemetryLoggerProvider, which is configured to export logs to ConsoleExporter. ConsoleExporter simply displays it on the console.

Note for different application types

Certain types of applications (e.g. ASP.NET Core and .NET Worker) have an ILogger based logging pipeline set up by default. In such apps, enabling OpenTelemetry should be done by adding OpenTelemetry as a provider to the existing logging pipeline, and users should not create a new LoggerFactory (which sets up a totally new logging pipeline). Also, obtaining ILogger instance could be done differently as well. See Example ASP.NET Core application for an example which shows how to add OpenTelemetry to the logging pipeline already setup by the application.

Learn more