Configure tracing with Telemetry API

Istio provides the ability to configure tracing options, such as sampling rate and adding custom tags to reported spans. This task shows you how to customize the tracing options with Telemetry API.

Before you begin

1. Ensure that your applications propagate tracing headers as described here.

2. Follow the tracing installation guide located under Integrations based on your preferred tracing backend to install the appropriate software and configure an extension provider.

Installation

In this example, we will send traces to Zipkin. Install Zipkin before you continue.

Configure an extension provider

Install Istio with an extension provider referring to the Zipkin service:

{{< text bash >}} $ cat <<EOF > ./tracing.yaml apiVersion: install.istio.io/v1alpha1 kind: IstioOperator spec: meshConfig: enableTracing: true defaultConfig: tracing: {} # disable legacy MeshConfig tracing options extensionProviders: - name: "zipkin" zipkin: service: zipkin.istio-system.svc.cluster.local port: 9411 EOF $ istioctl install -f ./tracing.yaml --skip-confirmation {{< /text >}}

Enable tracing

Enable tracing by applying the following configuration:

{{< text bash >}} $ kubectl apply -f - <<EOF apiVersion: telemetry.istio.io/v1 kind: Telemetry metadata: name: mesh-default namespace: istio-system spec: tracing:

• providers:
  • name: "zipkin" EOF {{< /text >}}

Verify the results

You can verify the results by accessing the Zipkin UI.

Customization

Customizing trace sampling

The sampling rate option can be used to control what percentage of requests get reported to your tracing system. This should be configured based upon your traffic in the mesh and the amount of tracing data you want to collect. The default rate is 1%.

{{< text bash >}} $ kubectl apply -f - <<EOF apiVersion: telemetry.istio.io/v1 kind: Telemetry metadata: name: mesh-default namespace: istio-system spec: tracing:

• providers:
  • name: "zipkin" randomSamplingPercentage: 100.00 EOF {{< /text >}}

Customizing tracing tags

Custom tags can be added to spans based on literals, environmental variables and client request headers in order to provide additional information in spans specific to your environment.

{{< warning >}} There is no limit on the number of custom tags that you can add, but tag names must be unique. {{< /warning >}}

You can customize the tags using any of the three supported options below.

1. Literal represents a static value that gets added to each span.

   {{< text yaml >}} apiVersion: telemetry.istio.io/v1 kind: Telemetry metadata: name: mesh-default namespace: istio-system spec: tracing:

   • providers:
     • name: "zipkin" randomSamplingPercentage: 100.00 customTags: "provider": literal: value: "zipkin" {{< /text >}}

2. Environmental variables can be used where the value of the custom tag is populated from a workload proxy environment variable.

   {{< text yaml >}} apiVersion: telemetry.istio.io/v1 kind: Telemetry metadata: name: mesh-default namespace: istio-system spec: tracing: - providers: - name: "zipkin" randomSamplingPercentage: 100.00 customTags: "cluster_id": environment: name: ISTIO_META_CLUSTER_ID defaultValue: Kubernetes # optional {{< /text >}}

   {{< warning >}} In order to add custom tags based on environmental variables, you must modify the istio-sidecar-injector ConfigMap in your root Istio system namespace. {{< /warning >}}

3. Client request header option can be used to populate tag value from an incoming client request header.

   {{< text yaml >}} apiVersion: telemetry.istio.io/v1 kind: Telemetry metadata: name: mesh-default namespace: istio-system spec: tracing: - providers: - name: "zipkin" randomSamplingPercentage: 100.00 customTags: my_tag_header: header: name: <CLIENT-HEADER> defaultValue: <VALUE> # optional {{< /text >}}

Customizing tracing tag length

By default, the maximum length for the request path included as part of the HttpUrl span tag is 256. To modify this maximum length, add the following to your tracing.yaml file.

{{< text yaml >}} apiVersion: install.istio.io/v1alpha1 kind: IstioOperator spec: meshConfig: enableTracing: true defaultConfig: tracing: {} # disable legacy tracing options via MeshConfig extensionProviders: - name: "zipkin" zipkin: service: zipkin.istio-system.svc.cluster.local port: 9411 maxTagLength: <VALUE> {{< /text >}}