---
title: Telemetry API
description: This task shows you how to configure the Telemetry API.
weight: 0
keywords: [telemetry]
owner: istio/wg-policies-and-telemetry-maintainers
test: no
---

Istio provides a [Telemetry API](/docs/reference/config/telemetry/) that enables flexible configuration of
[metrics](/docs/tasks/observability/metrics/), [access logs](/docs/tasks/observability/logs/), and [tracing](/docs/tasks/observability/distributed-tracing/).

## Using the API

### Scope, Inheritance, and Overrides

Telemetry API resources inherit configuration from parent resources in the Istio configuration hierarchy:

1.  root configuration namespace (example: `istio-system`)
1.  local namespace (namespace-scoped resource with **no** workload `selector`)
1.  workload (namespace-scoped resource with a workload `selector`)

A Telemetry API resource in the root configuration namespace, typically `istio-system`, provides mesh-wide defaults for behavior.
Any workload-specific selector in the root configuration namespace will be ignored/rejected. It is not valid to define multiple
mesh-wide Telemetry API resources in the root configuration namespace.

Namespace-specific overrides for the mesh-wide configuration can be achieved by applying a new `Telemetry` resource in the desired
namespace (without a workload selector). Any fields specified in the namespace configuration will completely override
the field from the parent configuration (in the root configuration namespace).

Workload-specific overrides can be achieved by applying a new Telemetry resource in the desired namespace *with a workload selector*.

### Workload Selection

Individual workloads within a namespace are selected via a [`selector`](/docs/reference/config/type/workload-selector/#WorkloadSelector)
which allows label-based selection of workloads.

It is not valid to have two different `Telemetry` resources select the same workload using `selector`. Likewise, it is not valid to have two
distinct `Telemetry` resources in a namespace with no `selector` specified.

### Provider Selection

The Telemetry API uses the concept of providers to indicate the protocol or type of integration to use. Providers can be configured in [`MeshConfig`](/docs/reference/config/istio.mesh.v1alpha1/#MeshConfig-ExtensionProvider).

An example set of provider configuration in `MeshConfig` is:

{{< text yaml >}}
data:
  mesh: |-
      extensionProviders: # The following content defines two example tracing providers.
      - name: "localtrace"
        zipkin:
          service: "zipkin.istio-system.svc.cluster.local"
          port: 9411
          maxTagLength: 56
      - name: "cloudtrace"
        stackdriver:
          maxTagLength: 256
{{< /text >}}

For convenience, Istio comes with a few providers configured out of the box with default settings:

|Provider Name|Functionality|
|-------------|-------------|
|`prometheus` |Metrics|
|`stackdriver`|Metrics, Tracing, Access Logging|
|`envoy`      |Access Logging|

In additional, a [default provider](/docs/reference/config/istio.mesh.v1alpha1/#MeshConfig-DefaultProviders) can be set which
will be used when the `Telemetry` resources do not specify a provider.

## Examples

### Configuring mesh-wide behavior

Telemetry API resources inherit from the root configuration namespace for a mesh, typically `istio-system`. To configure
mesh-wide behavior, add a new (or edit the existing) `Telemetry` resource in the root configuration namespace.

Here is an example configuration that uses the provider configuration from the prior section:

{{< text yaml >}}
apiVersion: telemetry.istio.io/v1alpha1
kind: Telemetry
metadata:
  name: mesh-default
  namespace: istio-system
spec:
  tracing:
  - providers:
    - name: localtrace
    customTags:
      foo:
        literal:
          value: bar
    randomSamplingPercentage: 100
{{< /text >}}

This configuration overrides the default provider from `MeshConfig`, setting the mesh default to be the `localtrace`
provider. It also sets the mesh-wide sampling percentage to be `100`, and configures a tag to be added to all trace
spans with a name of `foo` and a value of `bar`.

### Configuring namespace-scoped tracing behavior

To tailor the behavior for individual namespaces, add a `Telemetry` resource to the desired namespace.
Any fields specified in the namespace resource will completely override the inherited field configuration from the configuration hierarchy.
For example:

{{< text yaml >}}
apiVersion: telemetry.istio.io/v1alpha1
kind: Telemetry
metadata:
  name: namespace-override
  namespace: myapp
spec:
  tracing:
  - customTags:
      userId:
        header:
          name: userId
          defaultValue: unknown
{{< /text >}}

When deployed into a mesh with the prior mesh-wide example configuration, this will result in
tracing behavior in the `myapp` namespace that sends trace spans to the `localtrace` provider and
randomly selects requests for tracing at a `100%` rate, but that sets custom tags for each span with
a name of `userId` and a value taken from the `userId` request header.
Importantly, the `foo: bar` tag from the parent configuration will not be used in the `myapp` namespace.
The custom tags behavior completely overrides the behavior configured in the `mesh-default.istio-system` resource.

{{< tip >}}
Any configuration in a `Telemetry` resource completely overrides configuration of its parent resource in the configuration hierarchy. This includes provider selection.
{{< /tip >}}

### Configuring workload-specific behavior

To tailor the behavior for individual workloads, add a `Telemetry` resource to the desired namespace and use a
`selector`. Any fields specified in the workload-specific resource will completely override the inherited
field configuration from the configuration hierarchy.

For example:

{{< text yaml >}}
apiVersion: telemetry.istio.io/v1alpha1
kind: Telemetry
metadata:
  name: workload-override
  namespace: myapp
spec:
  selector:
    matchLabels:
      service.istio.io/canonical-name: frontend
  tracing:
  - disableSpanReporting: true
{{< /text >}}

In this case, tracing will be disabled for the `frontend` workload in the `myapp` namespace.
Istio will still forward the tracing headers, but no spans will be reported to the configured tracing provider.

{{< tip >}}
It is not valid to have two `Telemetry` resources with workload selectors select the same workload. In those cases, behavior is undefined.
{{< /tip >}}