---
title: "tracing block | Grafana Agent documentation"
description: "Learn about the tracing configuration block"
---

# tracing block

`tracing` is an optional configuration block used to customize how Grafana Agent Flow produces traces. `tracing` is specified without a label and can only be provided once per configuration file.

## Example

Alloy ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy

```alloy
tracing {
  sampling_fraction = 0.1

  write_to = [otelcol.exporter.otlp.tempo.input]
}

otelcol.exporter.otlp "tempo" {
  // Send traces to a locally running Tempo without TLS enabled.
  client {
    endpoint = env("TEMPO_OTLP_ENDPOINT")

    tls {
      insecure = true
    }
  }
}
```

## Arguments

The following arguments are supported:

Expand table

| Name                | Type                     | Description                                         | Default | Required |
|---------------------|--------------------------|-----------------------------------------------------|---------|----------|
| `sampling_fraction` | `number`                 | Fraction of traces to keep.                         | `0.1`   | no       |
| `write_to`          | `list(otelcol.Consumer)` | Inputs from `otelcol` components to send traces to. | `[]`    | no       |

The `write_to` argument controls which components to send traces to for processing. The elements in the array can be any `otelcol` component that accept traces, including processors and exporters. When `write_to` is set to an empty array `[]`, all traces are dropped.

> **NOTE**: Any traces generated before the `tracing` block has been evaluated, such as at the early start of the process’ lifetime, are dropped.

The `sampling_fraction` argument controls what percentage of generated traces should be sent to the consumers specified by `write_to`. When set to `1` or greater, 100% of traces are kept. When set to `0` or lower, 0% of traces are kept.

## Blocks

The following blocks are supported inside the definition of `tracing`:

Expand table

| Hierarchy                   | Block                                  | Description                                                  | Required |
|-----------------------------|----------------------------------------|--------------------------------------------------------------|----------|
| sampler                     | [sampler](#sampler-block)              | Define custom sampling on top of the base sampling fraction. | no       |
| sampler > jaeger\_remote | [jaeger\_remote](#jaeger_remote-block) | Retrieve sampling information via a Jaeger remote sampler.   | no       |

The `>` symbol indicates deeper levels of nesting. For example, `sampler > jaeger_remote` refers to a `jaeger_remote` block defined inside an `sampler` block.

### sampler block

The `sampler` block contains a definition of a custom sampler to use. The `sampler` block supports no arguments and is controlled fully through inner blocks.

It is invalid to define more than one sampler to use in the `sampler` block.

### jaeger\_remote block

The `jaeger_remote` block configures the retrieval of sampling information through a remote server that exposes Jaeger sampling strategies.

Expand table

| Name               | Type       | Description                                                | Default                            | Required |
|--------------------|------------|------------------------------------------------------------|------------------------------------|----------|
| `url`              | `string`   | URL to retrieve sampling strategies from.                  | `"http://127.0.0.1:5778/sampling"` | no       |
| `max_operations`   | `number`   | Limit number of operations which can have custom sampling. | `256`                              | no       |
| `refresh_interval` | `duration` | Frequency to poll the URL for new sampling strategies.     | `"1m"`                             | no       |

The remote sampling strategies are retrieved from the URL specified by the `url` argument, and polled for updates on a timer. The frequency for how often polling occurs is controlled by the `refresh_interval` argument.

Requests to the remote sampling strategies server are made through an HTTP `GET` request to the configured `url` argument. A `service=grafana-agent` query parameter is always added to the URL to allow the server to respond with service-specific strategies. The HTTP response body is read as JSON matching the schema specified by Jaeger’s [`strategies.json` file](https://www.jaegertracing.io/docs/1.22/sampling/#collector-sampling-configuration).

The `max_operations` limits the amount of custom span names that can have custom sampling rules. If the remote sampling strategy exceeds the limit, sampling decisions fall back to the default sampler.