# Observability - .NET SDK

> Explore Temporal SDK observability features for Metrics, Tracing, Logging, and Visibility. Track Workflow Executions, set up Prometheus endpoints, customize metrics, configure tracing, and more.

This page covers features related to viewing the state of the application, including:

- [Metrics](#metrics)
- [Tracing](#tracing)
- [Logging](#logging)
- [Visibility](#visibility)

The observability feature guide covers the many ways to view the current state of your [Temporal Application](/temporal#temporal-application).
This includes the ways to view which [Workflow Executions](/workflow-execution) are tracked by the [Temporal Platform](/temporal#temporal-platform) and the state of any specified Workflow Execution, either currently or at points of an execution.

## Emit metrics 

Each Temporal SDK is capable of emitting an optional set of metrics from either the Client or the Worker process.
For a complete list of metrics capable of being emitted, see the [SDK metrics reference](/references/sdk-metrics).

- For an overview of Prometheus and Grafana integration, refer to the [Monitoring](/self-hosted-guide/monitoring) guide.
- For a list of metrics, see the [SDK metrics reference](/references/sdk-metrics).
- For an end-to-end example that exposes metrics with the .NET SDK, refer to the [samples-dotnet](https://github.com/temporalio/samples-dotnet/tree/main/src/OpenTelemetry) repo.

Metrics in .NET are configured on the `Metrics` property of the `Telemetry` property on the `TemporalRuntime`. That object should be created globally and should be used for all clients; therefore, you should configure this before any other Temporal code.

### Set a Prometheus endpoint

The following example exposes a Prometheus endpoint on port `9000`.

```csharp
using Temporalio.Client;
using Temporalio.Runtime;

var runtime = new TemporalRuntime(new()
{
    Telemetry = new() { Metrics = new() { Prometheus = new("0.0.0.0:9000") } },
});
var client = await Temporalio.ConnectAsync(new("localhost:7233") { Runtime = runtime });
```

### Set a custom metric meter

A custom metric meter can be set on the telemetry options to handle metrics programmatically.
The [Temporalio.Extensions.DiagnosticSource](https://github.com/temporalio/sdk-dotnet/tree/main/src/Temporalio.Extensions.DiagnosticSource) extension provides a custom metric meter implementation that sends all metrics to a [System.Diagnostics.Metrics.Meter](https://learn.microsoft.com/en-us/dotnet/api/system.diagnostics.metrics.meter) instance.

```csharp
using System.Diagnostics.Metrics;
using Temporalio.Client;
using Temporalio.Extensions.DiagnosticSource;
using Temporalio.Runtime;

// Create .NET meter
using var meter = new Meter("My.Meter");
// Can create MeterListener or OTel meter provider here...

// Create Temporal runtime with a custom metric meter for that meter
var runtime = new TemporalRuntime(new()
{
    Telemetry = new()
    {
        Metrics = new() { CustomMetricMeter = new CustomMetricMeter(meter) },
    },
});
var client = await Temporalio.ConnectAsync(new("localhost:7233") { Runtime = runtime });
```

## Setup Tracing 

Tracing allows you to view the call graph of a Workflow along with its Activities, Nexus Operations, and any Child Workflows.

To configure OpenTelemetry tracing in .NET, use the [Temporalio.Extensions.OpenTelemetry](https://github.com/temporalio/sdk-dotnet/tree/main/src/Temporalio.Extensions.OpenTelemetry) extension.

The [`Temporalio.Extensions.OpenTelemetry.TracingInterceptor`](https://dotnet.temporal.io/api/Temporalio.Extensions.OpenTelemetry.TracingInterceptor.html) class can be set as an interceptor in the client options, or provided through a [Plugin](/develop/plugins-guide#interceptors) if you're building a reusable library.

When your Client is connected, spans are created for all Client calls, Activities, and Workflow invocations on the Worker.
Spans are created and serialized through the server to give one trace for a Workflow Execution.

## Log from a Workflow 

Logging enables you to record critical information during code execution.
Loggers create an audit trail and capture information about your Workflow's operation.
An appropriate logging level depends on your specific needs.
During development or troubleshooting, you might use debug or even trace.
In production, you might use info or warn to avoid excessive log volume.

The logger supports the following logging levels:

| Level   | Use                                                                                                       |
| ------- | --------------------------------------------------------------------------------------------------------- |
| `TRACE` | The most detailed level of logging, used for very fine-grained information.                               |
| `DEBUG` | Detailed information, typically useful for debugging purposes.                                            |
| `INFO`  | General information about the application's operation.                                                    |
| `WARN`  | Indicates potentially harmful situations or minor issues that don't prevent the application from working. |
| `ERROR` | Indicates error conditions that might still allow the application to continue running.                    |

The Temporal SDK core normally uses `WARN` as its default logging level.

Logging uses the .NET standard logging APIs.
The `LoggerFactory` can be set in the client.
The following example shows logging on the console and sets the level to `Information`.

```csharp
var client = await TemporalClient.ConnectAsync(new("localhost:7233")
{
    LoggerFactory = LoggerFactory.Create(builder =>
        builder.
            AddSimpleConsole(options => options.TimestampFormat = "[HH:mm:ss] ").
            SetMinimumLevel(LogLevel.Information)),
});
```

You can log from a Workflow using `Workflow.Logger` which is an instance of .NET's `ILogger`.

```csharp
Workflow.Logger.LogInformation("Given name: {Name}", name);
```

## Use Visibility APIs 

The term Visibility, within the Temporal Platform, refers to the subsystems and APIs that enable an operator to view Workflow Executions that currently exist within a Temporal Service.

### Use Search Attributes 

The typical method of retrieving a Workflow Execution is by its Workflow Id.

However, sometimes you'll want to retrieve one or more Workflow Executions based on another property. For example, imagine you want to get all Workflow Executions of a certain type that have failed within a time range, so that you can start new ones with the same arguments.

You can do this with [Search Attributes](/search-attribute).

- [Default Search Attributes](/search-attribute#default-search-attribute) like `WorkflowType`, `StartTime` and `ExecutionStatus` are automatically added to Workflow Executions.
- [Custom Search Attributes](/search-attribute#custom-search-attribute) can contain their own domain-specific data (like `customerId` or `numItems`).

The steps to using custom Search Attributes are:

- Create a new Search Attribute in your Temporal Service in the CLI or Web UI.
  - For example: `temporal operator search-attribute create --name CustomKeywordField --type Text`
    - Replace `CustomKeywordField` with the name of your Search Attribute.
    - Replace `Text` with a type value associated with your Search Attribute: `Text` | `Keyword` | `Int` | `Double` | `Bool` | `Datetime` | `KeywordList`
- Set the value of the Search Attribute for a Workflow Execution:
  - On the Client by including it as an option when starting the Execution.
  - In the Workflow by calling `UpsertTypedSearchAttributes`.
- Read the value of the Search Attribute:
  - On the Client by calling `Describe` on a `WorkflowHandle`.
  - In the Workflow by looking at `WorkflowInfo`.
- Query Workflow Executions by the Search Attribute using a [List Filter](/list-filter):
  - [In the Temporal CLI](/cli/command-reference/operator#list-2)
  - In code by calling `ListWorkflowsAsync`.

### List Workflow Executions 

Use the [ListWorkflowsAsync()](https://dotnet.temporal.io/api/Temporalio.Client.ITemporalClient.html#Temporalio_Client_ITemporalClient_ListWorkflowsAsync_System_String_Temporalio_Client_WorkflowListOptions_) method on the Client and pass a [List Filter](/list-filter) as an argument to filter the listed Workflows.
The result is an async enumerable.

```csharp
await foreach (var wf in client.ListWorkflowsAsync("WorkflowType='GreetingWorkflow'"))
{
    Console.WriteLine("Workflow: {0}", wf.Id);
}
```

### Set Custom Search Attributes 

After you've created custom Search Attributes in your Temporal Service (using `temporal operator search-attribute create`or the Cloud UI), you can set the values of the custom Search Attributes when starting a Workflow.

To set custom Search Attributes, use the `TypedSearchAttributes` property on `WorkflowOptions` for `StartWorkflowAsync` or `ExecuteWorkflowAsync`.
Typed search attributes are a `SearchAttributeCollection` created with a builder.

```csharp
// This only needs to be created once, so it is common to make it a static readonly even though we
// create inline here for demonstration
var myKeywordAttributeKey = SearchAttributeKey.CreateKeyword("MyKeywordAttribute");

// Start workflow with the search attribute collection
var handle = await client.StartWorkflowAsync(
    (MyWorkflow wf) => wf.RunAsync(),
    new(id: "my-workflow-id", taskQueue: "my-task-queue")
    {
        TypedSearchAttributes = new SearchAttributeCollection.Builder().
            Set(myKeywordAttributeKey, "SomeKeywordValue").
            ToSearchAttributeCollection(),
    });
```

### Upsert Search Attributes 

You can upsert Search Attributes to add, update, or remove Search Attributes from within Workflow code.

To upsert custom Search Attributes, use the [`UpsertTypedSearchAttributes()`](https://dotnet.temporal.io/api/Temporalio.Workflows.Workflow.html#Temporalio_Workflows_Workflow_UpsertTypedSearchAttributes_Temporalio_Workflows_SearchAttributeUpdate___) method with a set of updates.
Keys can be predefined for reuse.

```csharp
// These only need to be created once, so it is common to make them static readonly even though we
// create inline here for demonstration
var myKeywordAttributeKey = SearchAttributeKey.CreateKeyword("MyKeywordAttribute");
var myTextAttributeKey = SearchAttributeKey.CreateText("MyTextAttribute");

// Add/Update the keyword one and remove the text one
Workflow.UpsertTypedSearchAttributes(
    myKeywordAttributeKey.ValueSet("SomeKeywordValue"),
    myTextAttributeKey.ValueUnset());
```