Customizing Istio Metrics

This task shows you how to customize the metrics that Istio generates.

Istio generates telemetry that various dashboards consume to help you visualize your mesh. For example, dashboards that support Istio include:

• Grafana
• Kiali
• Prometheus

By default, Istio defines and generates a set of standard metrics (e.g. requests_total), but you can also customize them and create new metrics.

Custom statistics configuration

Istio uses the Envoy proxy to generate metrics and provides its configuration in the EnvoyFilter at manifests/charts/istio-control/istio-discovery/templates/telemetryv2_1.16.yaml.

Configuring custom statistics involves two sections of the EnvoyFilter: definitions and metrics. The definitions section supports creating new metrics by name, the expected value expression, and the metric type (counter, gauge, and histogram). The metrics section provides values for the metric dimensions as expressions, and allows you to remove or override the existing metric dimensions. You can modify the standard metric definitions using tags_to_remove or by re-defining a dimension. These configuration settings are also exposed as istioctl installation options, which allow you to customize different metrics for gateways and sidecars as well as for the inbound or outbound direction.

For more information, see Stats Config reference.

Before you begin

Install Istio in your cluster and deploy an application. Alternatively, you can set up custom statistics as part of the Istio installation.

The Bookinfo sample application is used as the example application throughout this task.

Enable custom metrics

1. The default telemetry v2 EnvoyFilter configuration is equivalent to the following installation options:

   apiVersion: install.istio.io/v1alpha1
   kind: IstioOperator
   spec:
     values:
       telemetry:
         v2:
           prometheus:
             configOverride:
               inboundSidecar:
                 disable_host_header_fallback: false
               outboundSidecar:
                 disable_host_header_fallback: false
               gateway:
                 disable_host_header_fallback: true
   

   To customize telemetry v2 metrics, for example, to add request_host and destination_port dimensions to the requests_total metric emitted by both gateways and sidecars in the inbound and outbound direction, change the installation options as follows:

   $ cat <<EOF > ./custom_metrics.yaml
   apiVersion: install.istio.io/v1alpha1
   kind: IstioOperator
   spec:
     values:
       telemetry:
         v2:
           prometheus:
             configOverride:
               inboundSidecar:
                 metrics:
                   - name: requests_total
                     dimensions:
                       destination_port: string(destination.port)
                       request_host: request.host
               outboundSidecar:
                 metrics:
                   - name: requests_total
                     dimensions:
                       destination_port: string(destination.port)
                       request_host: request.host
               gateway:
                 metrics:
                   - name: requests_total
                     dimensions:
                       destination_port: string(destination.port)
                       request_host: request.host
   EOF
   # istioctl install -f custom_metrics.yaml
   

2. Apply the following annotation to all injected pods with the list of the dimensions to extract into a Prometheus time series using the following command:

   apiVersion: apps/v1
   kind: Deployment
   spec:
     template: # pod template
       metadata:
         annotations:
           sidecar.istio.io/extraStatTags: destination_port,request_host
   

   To enable extra tags mesh wide, you can add extraStatTags to your mesh config:

   meshConfig:
     defaultConfig:
       extraStatTags:
        - destination_port
        - request_host
   

Verify the results

Send traffic to the mesh. For the Bookinfo sample, visit http://$GATEWAY_URL/productpage in your web browser or issue the following command:

$ curl "http://$GATEWAY_URL/productpage"

Use the following command to verify that Istio generates the data for your new or modified dimensions:

$ kubectl exec "$(kubectl get pod -l app=productpage -o jsonpath='{.items[0].metadata.name}')" -c istio-proxy -- curl -sS 'localhost:15000/stats/prometheus' | grep istio_requests_total

For example, in the output, locate the metric istio_requests_total and verify it contains your new dimension.

Use expressions for values

The values in the metric configuration are common expressions, which means you must double-quote strings in JSON, e.g. “‘string value’”. Unlike Mixer expression language, there is no support for the pipe (|) operator, but you can emulate it with the has or in operator, for example:

has(request.host) ? request.host : "unknown"

For more information, see Common Expression Language.

Istio exposes all standard Envoy attributes. Peer metadata is available as attributes upstream_peer for outbound and downstream_peer for inbound with the following fields:

For example, the expression for the peer app label to be used in an outbound configuration is upstream_peer.labels['app'].value.

For more information, see configuration reference.