1. Config ingestion (inputs to the system)
1. Config translation
1. Config serving (XDS)

### Config Ingestion

Istio reads from over 20 different resources types, and aggregates them together to build the proxy configuration. These resources can be sourced from Kubernetes (via watches), files, or over xDS; Kubernetes is by far the most common usage, though.

Primarily for historical reasons, ingestion is split into a few components.

          operator: DoesNotExist
    objectSelector:
      matchExpressions:
        - key: sidecar.istio.io/inject
          operator: NotIn
          values:
            - "false"
    reinvocationPolicy: Never
    rules:
      - apiGroups:
          - ""
        apiVersions:
          - v1
        operations:
          - CREATE
        resources:
          - pods
        scope: '*'
    sideEffects: None

apiVersion: v1
name: istio-default
# This version is never actually shipped. istio/release-builder will replace it at build-time
# with the appropriate version
version: 1.0.0
appVersion: 1.0.0
description: Helm chart for istio default revision components.
keywords:
  - istio
sources:
  - https://github.com/istio/istio
engine: gotpl

            "lineInterpolation": "linear",
            "lineWidth": 1,
            "pointSize": 5,
            "scaleDistribution": {
              "type": "linear"
            },
            "showPoints": "never",
            "spanNulls": false,
            "stacking": {
              "group": "A",
              "mode": "none"
            },
            "thresholdsStyle": {
              "mode": "off"
            }

  //
  // Well-known Kubernetes signers are:
  //  1. "kubernetes.io/kube-apiserver-client": issues client certificates that can be used to authenticate to kube-apiserver.
  //   Requests for this signer are never auto-approved by kube-controller-manager, can be issued by the "csrsigning" controller in kube-controller-manager.

}

// AdmissionResponse describes an admission response.
message AdmissionResponse {
  // UID is an identifier for the individual request/response.
  // This must be copied over from the corresponding AdmissionRequest.
  optional string uid = 1;

  // Allowed indicates whether or not the admission request was permitted.
  optional bool allowed = 2;

  // A list of daemon sets.
  repeated DaemonSet items = 2;
}

// DaemonSetSpec is the specification of a daemon set.
message DaemonSetSpec {
  // A label query over pods that are managed by the daemon set.
  // Must match in order to be controlled.
  // It must match the pod template's labels.

All metrics returned are from server-side reports. This means that latencies
and error rates are from the perspective of the service itself and not of an
individual client (or aggregate set of clients). Rates and latencies are
calculated over a time interval of 1 minute.
`,
		Example: `  # Retrieve workload metrics for productpage-v1 workload
  istioctl experimental metrics productpage-v1

  # Retrieve workload metrics for various services with custom duration

  // A list of daemon sets.
  repeated DaemonSet items = 2;
}

// DaemonSetSpec is the specification of a daemon set.
message DaemonSetSpec {
  // A label query over pods that are managed by the daemon set.
  // Must match in order to be controlled.
  // If empty, defaulted to labels on Pod template.

    # Setting this to `IfNeeded` will result in the sidecar injector being run again if additional mutations occur.
    reinvocationPolicy: Never
    rewriteAppHTTPProbe: true
    # Templates defines a set of custom injection templates that can be used. For example, defining:
    #
    # templates:
    #   hello: |
    #     metadata:
    #       labels: