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Parameters - Post (experimental feature)

Captures parameters for one or more methods each time they are called. Parameters are logged inside the target application using its ILogger.

Note

Unlike other artifacts, parameters do not support being sent to an egress provider.

Important

This feature is not enabled by default and requires configuration to be enabled. See Enabling for more information.

Enabling

This feature is currently marked as experimental and so needs to be explicitly enabled. The following configuration must be set for the feature to be used.

"InProcessFeatures": {
    "ParameterCapturing": {
        "Enabled": true
    }
}

HTTP Route

POST /parameters?pid={pid}&uid={uid}&name={name}&durationSeconds={durationSeconds}&tags={tags} HTTP/1.1

Note

Process information (IDs, names, environment, etc) may change between invocations of these APIs. Processes may start or stop between API invocations, causing this information to change.

Host Address

The default host address for these routes is https://localhost:52323. This route is only available on the addresses configured via the --urls command line parameter and the DOTNETMONITOR_URLS environment variable.

URI Parameters

Name In Required Type Description
pid query false int The ID of the process.
uid query false guid A value that uniquely identifies a runtime instance within a process.
name query false string The name of the process.
durationSeconds query false int The duration of the parameters operation in seconds. Default is 30. Min is -1 (indefinite duration). Max is 2147483647.
tags query false string A comma-separated list of user-readable identifiers for the operation.

See ProcessIdentifier for more details about the pid, uid, and name parameters.

If none of pid, uid, or name are specified, parameters from the default process will be captured. Attempting to capture parameters from the default process when the default process cannot be resolved will fail.

Authentication

Authentication is enforced for this route. See Authentication for further information.

Allowed schemes:

  • Bearer
  • Negotiate (Windows only, running as unelevated)

Request Body

A request body of type CaptureParametersConfiguration is required.

The expected content type is application/json.

Responses

Name Type Description Content Type
202 Accepted The artifact has begun being collected.
400 Bad Request ValidationProblemDetails An error occurred due to invalid input. The response body describes the specific problem(s). application/problem+json
401 Unauthorized Authentication is required to complete the request. See Authentication for further information.
429 Too Many Requests There are too many parameters requests at this time. Try to request parameters at a later time. application/problem+json

UserCode vs SystemCode

Methods that belong to any of the following namespaces are considered SystemCode:

  • Microsoft.*
  • System.*

All other methods are considered UserCode. UserCode methods will have their parameters captured inline, meaning that the added log statements are performed synchronously inside your method, preserving the logger's scope.

SystemCode methods will have their parameters captured asynchronously and without scope information.

The examples include a mixture of UserCode and SystemCode to help showcase the difference.

Logger Categories

The following logger categories are used inside the target application when capturing parameters:

Category Name Description
DotnetMonitor.ParameterCapture.UserCode Parameters captured in methods considered UserCode.
DotnetMonitor.ParameterCapture.SystemCode Parameters captured in methods considered SystemCode.
DotnetMonitor.ParameterCapture.Service Diagnostic messages by dotnet-monitor, such as when parameter capturing starts, stops, or is unable to find a requested method.

Examples

Sample Request

POST /parameters?pid=21632&durationSeconds=60 HTTP/1.1
Host: localhost:52323
Authorization: Bearer fffffffffffffffffffffffffffffffffffffffffff=

{
    "methods": [
        {
            "moduleName": "SampleWebApp.dll",
            "typeName": "SampleWebApp.Controllers.HomeController",
            "methodName": "Index"
        },
        {
            "moduleName": "System.Private.CoreLib.dll",
            "typeName": "System.String",
            "methodName": "Concat"
        }
    ]
}

Sample Response

HTTP/1.1 202 Accepted
Content-Type: application/json
Location: localhost:52323/operations/67f07e40-5cca-4709-9062-26302c484f18

Sample Output (Target Application)

info: DotnetMonitor.ParameterCapture.UserCode[0]
      => SpanId:e40e62cffe1cf1cb, TraceId:c76b911969aa8abcf335907e96c62b33, ParentId:0000000000000000 => ConnectionId:0HMT2D6L8GT2Q => RequestPath:/ RequestId:0HMT2D6L8GT2Q:00000003 => SampleWebApp.Controllers.HomeController.Index (SampleWebApp)
      SampleWebApp.Controllers.HomeController.Index(
        this: 'SampleWebApp.Controllers.HomeController',
        number: 10)
info: DotnetMonitor.ParameterCapture.SystemCode[0]
      System.String.Concat(
        str0: 'firstString',
        str1: '.secondString')

Supported Runtimes

Operating System Runtime Version
Windows .NET 7+
Linux .NET 7+
MacOS .NET 7+

Additional Requirements

  • The target application must use ASP.NET Core.
  • The target application cannot have Hot Reload enabled.
  • dotnet-monitor must be set to Listen mode, and the target application must start suspended. See diagnostic port configuration for information on how to do this.
  • The target application must have ILogger available via ASP.NET Core's dependency injection.
  • This feature relies on a hosting startup assembly. If the target application disabled automatic loading of these, this feature will not be available.
  • This feature relies on a ICorProfilerCallback implementation. If the target application is already using an ICorProfiler that isn't notify-only, this feature will not be available.
  • If a target application is using .NET 7 then the dotnet-monitor startup hook must be configured. This is automatically done in .NET 8+.

Additional Notes

Unsupported Parameters

Currently some types of parameters are unable to be captured. When a method contains one of these unsupported types, the parameter's value will be represented as <unsupported>. Other parameters in the method will still be captured so long as they are supported. The most common unsupported types are listed below.

Parameter Type Example
Generic type parameters MyMethod<T>(T t)
Parameters with pass-by-reference modifiers (in, out, and ref) ref int i
Nullable value types int?
Pointers void*
Tuples (int, int)

When to use pid vs uid

See Process ID pid vs Unique ID uid for clarification on when it is best to use either parameter.