# Startup diagnostics

<!-- Version variant: core_9; default: [/nservicebus/hosting/startup-diagnostics.md](/nservicebus/hosting/startup-diagnostics.md) -->


> [!NOTE]
> This document does not apply to Azure Function hosts. For Azure Function hosts, see [Azure Function Isolated Worker diagnostics](/nservicebus/hosting/azure-functions-service-bus/index.md#configuration-startup-diagnostics).

To make troubleshooting easier, diagnostic information is collected during endpoint startup and written to a `.diagnostics` sub-folder in the host output directory.

> [!NOTE]
> By default, the output directory is called `AppDomain.CurrentDomain.BaseDirectory`, except for web applications where `App_Data` is used instead.

To change the output path:

<!-- snippet: SetDiagnosticsPath -->

```cs
endpointConfiguration.SetDiagnosticsPath("myCustomPath");
```

<!-- endsnippet -->

At every endpoint startup the current diagnostics will be written to `{endpointName}-configuration.txt`. If possible, attach this file to support requests.

> [!WARNING]
> The structure and format of the data produced should not be considered stable or parsable. Nodes may be added, removed, or moved in minor and patch versions.


### Sample content

Sample partial content of the startup diagnostics (formatted for readability):

<!-- snippet: StartUpDiagnosticsWriter -->

```txt
{
  "Container": {
    "Type": "internal"
  },
  "Endpoint": {
    "Name": "StartUpDiagnosticsWriter",
    "SendOnly": false,
    "NServiceBusVersion": "9.2.7"
  },
  "Features": [
    {
      "Name": "NServiceBus.OpenTelemetryFeature",
      "EnabledByDefault": false,
      "Active": false,
      "PrerequisiteStatus": null,
      "Dependencies": [],
      "Version": "9.2.7",
      "StartupTasks": null,
      "DependenciesAreMet": false
    },
...
```

<!-- endsnippet -->



## Writing to other targets

To take full control of how diagnostics are written:

<!-- snippet: CustomDiagnosticsWriter -->

```cs
endpointConfiguration.CustomDiagnosticsWriter(
    (diagnostics, ct) =>
    {
        //custom logic to write data
        return Task.CompletedTask;
    });
```

<!-- endsnippet -->


## Adding startup diagnostics sections

To extend the startup diagnostics with custom sections:

<!-- snippet: CustomDiagnosticsSection -->

```cs
settings.AddStartupDiagnosticsSection(
    sectionName: "MySection",
    section: new
    {
        SomeSetting = "some data",
        SomeOtherSetting = 10
    });
```

<!-- endsnippet -->

Settings can be accessed from a [feature](/nservicebus/pipeline/features.md#feature-setup) or via the [endpoint configuration](/nservicebus/pipeline/features.md#feature-settings-endpointconfiguration).