# Istio CNI Node Agent

The Istio CNI Node Agent is responsible for several things

- Install an Istio CNI plugin binary on each node's filesystem, updating that node's CNI config in e.g (`/etc/cni/net.d`), and watching the config and binary paths to reinstall if things are modified.

The `Workload` aims to represent everything about a workload (generally a `Pod` or `WorkloadEntry`).
This includes things like its IP address, identity, metadata (name, namespace, app, version, etc), and whether it has a waypoint proxy associated.

The `Service` aims to represent everything about a service (generally a `Service` or `ServiceEntry`).
This includes things like its IP addresses, ports and an associated waypoint proxy if it has one.

### Authorization Type

// For a given StorageClass, this describes the available capacity in a
// particular topology segment.  This can be used when considering where to
// instantiate new PersistentVolumes.
//
// For example this can express things like:
// - StorageClass "standard" has "1234 GiB" available in "topology.kubernetes.io/zone=us-east1"
// - StorageClass "localssd" has "10 GiB" available in "kubernetes.io/hostname=knode-abc123"
//

  // +listType=map
  // +listMapKey=name
  // +optional
  repeated ResourceClaimSchedulingStatus resourceClaims = 1;
}

// ResourceClaim describes which resources are needed by a resource consumer.
// Its status tracks whether the resource has been allocated and what the
// resulting attributes are.
//
// This is an alpha type and requires enabling the DynamicResourceAllocation
// feature gate.
message ResourceClaim {

// For a given StorageClass, this describes the available capacity in a
// particular topology segment.  This can be used when considering where to
// instantiate new PersistentVolumes.
//
// For example this can express things like:
// - StorageClass "standard" has "1234 GiB" available in "topology.kubernetes.io/zone=us-east1"
// - StorageClass "localssd" has "10 GiB" available in "kubernetes.io/hostname=knode-abc123"
//

```console
helm install istio-cni istio/cni -n kube-system
```

Installation in `kube-system` is recommended to ensure the [`system-node-critical`](https://kubernetes.io/docs/tasks/administer-cluster/guaranteed-scheduling-critical-addon-pods/)
`priorityClassName` can be used. You can install in other namespace only on K8S clusters that allow
'system-node-critical' outside of kube-system.

## Configuration

  // Pod Topology Spread treats "global minimum" as 0, and then the calculation of Skew is performed.
  // And when the number of eligible domains with matching topology keys equals or greater than minDomains,
  // this value has no effect on scheduling.
  // As a result, when the number of eligible domains is less than minDomains,

// For a given StorageClass, this describes the available capacity in a
// particular topology segment.  This can be used when considering where to
// instantiate new PersistentVolumes.
//
// For example this can express things like:
// - StorageClass "standard" has "1234 GiB" available in "topology.kubernetes.io/zone=us-east1"
// - StorageClass "localssd" has "10 GiB" available in "kubernetes.io/hostname=knode-abc123"
//

  // Clients can use the appropriate server address as per the CIDR that they match.
  // In case of multiple matches, clients should use the longest matching CIDR.
  // The server returns only those CIDRs that it thinks that the client can match.
  // For example: the master will return an internal IP CIDR only, if the client reaches the server using an internal IP.

Often, these handlers are adding something to the queue like `client.AddEventHandler(controllers.ObjectHandler(queue.AddObject))`.
Construction should NOT actually start running all of these things, do I/O, or block in anyway.

Running the controller actually starts processing things.
Normally, this just means running the queue.
All informers created by `kube.Client` are kept track in the client, and started in one go with `RunAndWait` in one centralized call.