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Implemented assembly redirect for non-default AppDomain #4728

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Implemented assembly redirect for non-default AppDomain #4728

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5dce969
Enhance AppDomain config and assembly loading strategies
iskiselev Dec 24, 2025
79f29d2
Newly added config variable name changed to `OTEL_DOTNET_AUTO_APP_DOM…
iskiselev Dec 24, 2025
d44cd9d
Formated changelog
iskiselev Dec 24, 2025
ff52a59
Updated environment variable for AspNetTests
iskiselev Dec 25, 2025
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9 changes: 9 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -14,6 +14,15 @@ This component adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.h
- Support for [`NLog`](https://www.nuget.org/packages/NLog/)
logs instrumentation for versions `5.*` and `6.*` on .NET using duck typing
for zero-config auto-injection.
- Configuration `OTEL_DOTNET_AUTO_APP_DOMAIN_STRATEGY` added with ability to
use:
- `LoaderOptimizationSingleDomain` - all non-default application domains
will be forced to load with `LoaderOptimization.SingleDomain`, preventing
their assemblies loading as domain neutral;
- `AssemblyRedirect` - modify app config binding redirects to load required
assembly versions;
- `None` - do not use any special strategy for non-default application
domains.

### Changed

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26 changes: 14 additions & 12 deletions docs/config.md
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Expand Up @@ -27,6 +27,7 @@ with environment variables taking precedence over `App.config` or `Web.config` f
- `OTEL_LOG_LEVEL`
- `OTEL_DOTNET_AUTO_NETFX_REDIRECT_ENABLED`
- `OTEL_DOTNET_AUTO_SQLCLIENT_NETFX_ILREWRITE_ENABLED`
- `OTEL_DOTNET_AUTO_APP_DOMAIN_STRATEGY`

Example with `OTEL_SERVICE_NAME` setting:

Expand Down Expand Up @@ -420,18 +421,19 @@ Important environment variables include:

## Additional settings

| Environment variable | Description | Default value | Status |
|-----------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------|-----------------------------------------------------------------------------------------------------------------------------------|
| `OTEL_DOTNET_AUTO_TRACES_ENABLED` | Enables traces. | `true` | [Experimental](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/versioning-and-stability.md) |
| `OTEL_DOTNET_AUTO_OPENTRACING_ENABLED` | Enables OpenTracing tracer. | `false` | [Deprecated](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/versioning-and-stability.md) |
| `OTEL_DOTNET_AUTO_LOGS_ENABLED` | Enables logs. | `true` | [Experimental](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/versioning-and-stability.md) |
| `OTEL_DOTNET_AUTO_METRICS_ENABLED` | Enables metrics. | `true` | [Experimental](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/versioning-and-stability.md) |
| `OTEL_DOTNET_AUTO_NETFX_REDIRECT_ENABLED` | Enables automatic redirection of the assemblies used by the automatic instrumentation on the .NET Framework. | `true` | [Experimental](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/versioning-and-stability.md) |
| `OTEL_DOTNET_AUTO_TRACES_ADDITIONAL_SOURCES` | Comma-separated list of additional `System.Diagnostics.ActivitySource` names to be added to the tracer at the startup. Use it to capture manually instrumented spans. | | [Experimental](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/versioning-and-stability.md) |
| `OTEL_DOTNET_AUTO_TRACES_ADDITIONAL_LEGACY_SOURCES` | Comma-separated list of additional legacy source names to be added to the tracer at the startup. Use it to capture `System.Diagnostics.Activity` objects created without using the `System.Diagnostics.ActivitySource` API. | | [Experimental](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/versioning-and-stability.md) |
| `OTEL_DOTNET_AUTO_FLUSH_ON_UNHANDLEDEXCEPTION` | Controls whether the telemetry data is flushed when an [AppDomain.UnhandledException](https://docs.microsoft.com/en-us/dotnet/api/system.appdomain.unhandledexception) event is raised. Set to `true` when you suspect that you are experiencing a problem with missing telemetry data and also experiencing unhandled exceptions. | `false` | [Experimental](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/versioning-and-stability.md) |
| `OTEL_DOTNET_AUTO_METRICS_ADDITIONAL_SOURCES` | Comma-separated list of additional `System.Diagnostics.Metrics.Meter` names to be added to the meter at the startup. Use it to capture manually created metrics. | | [Experimental](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/versioning-and-stability.md) |
| `OTEL_DOTNET_AUTO_PLUGINS` | Colon-separated list of OTel SDK instrumentation plugin types, specified with the [assembly-qualified name](https://docs.microsoft.com/en-us/dotnet/api/system.type.assemblyqualifiedname?view=net-6.0#system-type-assemblyqualifiedname). *Note: This list must be colon-separated because the type names may include commas.* See more info on how to write plugins at [plugins.md](plugins.md). | | [Experimental](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/versioning-and-stability.md) |
| Environment variable | Description | Default value | Status |
|-----------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------|-----------------------------------------------------------------------------------------------------------------------------------|
| `OTEL_DOTNET_AUTO_TRACES_ENABLED` | Enables traces. | `true` | [Experimental](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/versioning-and-stability.md) |
| `OTEL_DOTNET_AUTO_OPENTRACING_ENABLED` | Enables OpenTracing tracer. | `false` | [Deprecated](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/versioning-and-stability.md) |
| `OTEL_DOTNET_AUTO_LOGS_ENABLED` | Enables logs. | `true` | [Experimental](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/versioning-and-stability.md) |
| `OTEL_DOTNET_AUTO_METRICS_ENABLED` | Enables metrics. | `true` | [Experimental](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/versioning-and-stability.md) |
| `OTEL_DOTNET_AUTO_NETFX_REDIRECT_ENABLED` | Enables automatic redirection of the assemblies used by the automatic instrumentation on the .NET Framework. | `true` | [Experimental](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/versioning-and-stability.md) |
| `OTEL_DOTNET_AUTO_TRACES_ADDITIONAL_SOURCES` | Comma-separated list of additional `System.Diagnostics.ActivitySource` names to be added to the tracer at the startup. Use it to capture manually instrumented spans. | | [Experimental](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/versioning-and-stability.md) |
| `OTEL_DOTNET_AUTO_TRACES_ADDITIONAL_LEGACY_SOURCES` | Comma-separated list of additional legacy source names to be added to the tracer at the startup. Use it to capture `System.Diagnostics.Activity` objects created without using the `System.Diagnostics.ActivitySource` API. | | [Experimental](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/versioning-and-stability.md) |
| `OTEL_DOTNET_AUTO_FLUSH_ON_UNHANDLEDEXCEPTION` | Controls whether the telemetry data is flushed when an [AppDomain.UnhandledException](https://docs.microsoft.com/en-us/dotnet/api/system.appdomain.unhandledexception) event is raised. Set to `true` when you suspect that you are experiencing a problem with missing telemetry data and also experiencing unhandled exceptions. | `false` | [Experimental](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/versioning-and-stability.md) |
| `OTEL_DOTNET_AUTO_METRICS_ADDITIONAL_SOURCES` | Comma-separated list of additional `System.Diagnostics.Metrics.Meter` names to be added to the meter at the startup. Use it to capture manually created metrics. | | [Experimental](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/versioning-and-stability.md) |
| `OTEL_DOTNET_AUTO_PLUGINS` | Colon-separated list of OTel SDK instrumentation plugin types, specified with the [assembly-qualified name](https://docs.microsoft.com/en-us/dotnet/api/system.type.assemblyqualifiedname?view=net-6.0#system-type-assemblyqualifiedname). *Note: This list must be colon-separated because the type names may include commas.* See more info on how to write plugins at [plugins.md](plugins.md). | | [Experimental](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/versioning-and-stability.md) |
| `OTEL_DOTNET_AUTO_APP_DOMAIN_STRATEGY` | Defines how AppDomains are handled by the Auto Instrumentation. Supported values: `LoaderOptimizationSingleDomain` - apply `LoaderOptimization.SingleDomain` for non-default AppDomain; `AssemblyRedirect` - modify bindingRedirect an app config; `None` - do not apply any workarounds | `LoaderOptimizationSingleDomain` | [Experimental](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/versioning-and-stability.md) |

## RuleEngine

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