Logging to elmah.io from OpenTelemetry

elmah.io provides an exporter for OpenTelemetry that will store log entries sent through OpenTelemetry in elmah.io.

Start by installing the Elmah.Io.OpenTelemetry package:

Install-Package Elmah.Io.OpenTelemetry -IncludePrerelease

dotnet add package Elmah.Io.OpenTelemetry --prerelease

<PackageReference Include="Elmah.Io.OpenTelemetry" Version="5.*" />

paket add Elmah.Io.OpenTelemetry

In the Program.cs file, configure the elmah.io exporter:

builder.Logging.AddOpenTelemetry(options =>
{
    options.AddElmahIoExporter(options =>
    {
        options.ApiKey = "API_KEY";
        options.LogId = new Guid("LOG_ID");
    });
});

Replace API_KEY with your API key (Where is my API key?) and LOG_ID (Where is my log ID?) with the log ID of the log you want to log to.

This will store log messages sent through OpenTelemetry in elmah.io. It is recommended only to send warnings and up to avoid spending your message quota with debug and information messages:

builder.Logging.AddFilter<OpenTelemetryLoggerProvider>("*", LogLevel.Warning);

Enriching log messages

The elmah.io exporter pulls as much information as possible, but you might want to enrich log messages with even more data. This can be done in numerous ways.

The export options provide an OnMessage action that you may already know from other client integrations:

options.AddElmahIoExporter(options =>
{
    // ...

    options.OnMessage = msg => msg.Version = "42";
});

You can include a service name on log messages using the ResourceBuilder part of OpenTelemetry:

builder.Logging.AddOpenTelemetry(options =>
{
    // ...

    options.SetResourceBuilder(ResourceBuilder
        .CreateEmpty()
        .AddService("Elmah.Io.OpenTelemetry.AspNetCore80"));
});

OpenTelemetry supports custom properties as Attributes. Global attributes can be added using the ResourceBuilder too:

options.SetResourceBuilder(ResourceBuilder
    .CreateEmpty()
    // ...
    .AddAttributes(new Dictionary<string, object>
    {
        { "deployment.environment", builder.Environment.EnvironmentName }
    }));

When logging messages through the ILogger interface, logging scopes can be configured by setting the IncludeScopes property:

builder.Logging.AddOpenTelemetry(options =>
{
    // ...

    options.IncludeScopes = true;
});

When enabling scopes, log messages can be enriched by wrapping the log message in a new scope:

using (logger.BeginScope(new { CorrelationId = "42" }))
{
    logger.LogInformation("A log message");
}

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