// StartupProbe indicates that the Pod has successfully initialized.
  // If specified, no other probes are executed until this completes successfully.
  // If this probe fails, the Pod will be restarted, just as if the livenessProbe failed.
  // This can be used to provide different probe parameters at the beginning of a Pod's lifecycle,
  // when it might take a long time to load data or warm a cache, than during steady-state operation.

#### Pushes

A push occurs when Istiod detects an update of some set of configuration is needed. This results in roughly the same result as a Request (new configuration is pushed to the client), and is just triggered by a different source.

### Default CA Flow through istio-agent

![CA Flow](docs/ca.svg)

A single SDS request from Envoy goes through a few different layers in istio-agent.

1. First, the request is handled by the SDS server. This is mostly just an intermediate translation layer exposing
   the `SecretManager` to Envoy, without much business logic. For each resource requested by Envoy, the SDS server
   will call `SecretManager.GenerateSecret(resourceName)`

Changes:
- separate namespace allows:
-- easier reconfig of just the gateway
-- TLS secrets and domain name management is isolated, for better security
-- simplified configuration
-- multiple versions of the ingress can be used, to minize upgrade risks

- the new chart uses the default namespace service account, and doesn't require
additional RBAC permissions.

- simplified label structure. Label change is not supported on upgrade.

Changes:
- separate namespace allows:
-- easier reconfig of just the gateway
-- TLS secrets and domain name management is isolated, for better security
-- simplified configuration
-- multiple versions of the ingress can be used, to minimize upgrade risks

- the new chart uses the default namespace service account, and doesn't require
additional RBAC permissions.

- simplified label and chart structure.

  // +optional
  optional string host = 1;

  // IngressRuleValue represents a rule to route requests for this IngressRule.
  // If unspecified, the rule defaults to a http catch-all. Whether that sends
  // just traffic matching the host to the default backend or all traffic to the
  // default backend, is left to the controller fulfilling the Ingress. Http is
  // currently the only supported IngressRuleValue.
  // +optional

  // The only valid values for this field are 'Apply' and 'Update'.
  optional string operation = 2;

  // APIVersion defines the version of this resource that this field set
  // applies to. The format is "group/version" just like the top-level
  // APIVersion field. It is necessary to track the version of a field
  // set because it cannot be automatically converted.
  optional string apiVersion = 3;

  In general, Istio does not fail on missing CRDs and prefers to treat these as if there were just zero resources for that client.
  The `NewDelayedInformer` abstracts that entirely, offering the same API as normal `kclient.Client`.
* Simple object filtering. Beyond just static filters on objects, `kclient` supports _dynamic filters_ that can change at runtime.

  // selector is the string-encoded form of a standard kubernetes label selector for the given metric.
  // When set, it is passed as an additional parameter to the metrics server for more specific metrics scoping
  // When unset, just the metricName will be used to gather metrics.
  // +optional
  optional k8s.io.apimachinery.pkg.apis.meta.v1.LabelSelector selector = 4;

  // averageValue is the target value of the average of the

  // selector is the string-encoded form of a standard kubernetes label selector for the given metric
  // When set, it is passed as an additional parameter to the metrics server for more specific metrics scoping.
  // When unset, just the metricName will be used to gather metrics.
  // +optional
  optional k8s.io.apimachinery.pkg.apis.meta.v1.LabelSelector selector = 2;
}

// MetricSpec specifies how to scale based on a single metric