# Istio operator code overview

## Introduction

This document covers primarily the code, with some background on how the design maps to it.
See the
[design doc](https://docs.google.com/document/d/11j9ZtYWNWnxQYnZy8ayZav1FMwTH6F6z6fkDYZ7V298/edit#heading=h.qex63c29z2to)
for a more complete design description. The operator code is divided roughly into five areas:

1. [IstioOperatorSpec API](#istiooperatorspec-api) and related infrastructure, which is expressed as a

  // index 2 in this pod). This syntax is chosen only to have some well-defined way of
  // referencing a part of an object.
  // TODO: this design is not final and this field is subject to change in the future.
  // +optional
  optional string fieldPath = 7;
}

// PersistentVolume (PV) is a storage resource provisioned by an administrator.

//
// <digit>           ::= 0 | 1 | ... | 9
// <digits>          ::= <digit> | <digit><digits>
// <number>          ::= <digits> | <digits>.<digits> | <digits>. | .<digits>
// <sign>            ::= "+" | "-"
// <signedNumber>    ::= <number> | <sign><number>
// <suffix>          ::= <binarySI> | <decimalExponent> | <decimalSI>
// <binarySI>        ::= Ki | Mi | Gi | Ti | Pi | Ei
//

  // At least one of ipv4 and ipv6 must be specified.
  // This field is immutable.
  // +optional
  optional string ipv6 = 4;
}

// IPAddress represents a single IP of a single IP Family. The object is designed to be used by APIs
// that operate on IP addresses. The object is used by the Service core API for allocation of IP addresses.
// An IP address can be represented in different formats, to guarantee the uniqueness of the IP,

    listKind: IPAddressPoolList
    plural: ipaddresspools
    singular: ipaddresspool
  scope: Namespaced
  versions:
  - additionalPrinterColumns:
    - jsonPath: .spec.autoAssign
      name: Auto Assign
      type: boolean
    - jsonPath: .spec.avoidBuggyIPs
      name: Avoid Buggy IPs
      type: boolean
    - jsonPath: .spec.addresses
      name: Addresses
      type: string
    name: v1beta1

# Updating charts and values.yaml

## Acceptable Pull Requests

Helm charts `values.yaml` represent a complex user facing API that tends to grow uncontrollably over time
due to design choices in Helm.
The underlying Kubernetes resources we configure have 1000s of fields; given enough users and bespoke use cases,
eventually someone will want to customize every one of those fields.

digraph { grpc -> ca [label="Send CSR gRPC Request"] subgraph cluster_istioagent { label = "Istio Agent" color="orange" sds SecretManager -> caClient [label="Sign CSR"] caClient -> grpc grpc -> TokenProvider [dir=none,label="Fetch JWT",color=purple] grpc -> cfiles [dir=none,label="Fetch Cert",color=purple] sds -> SecretManager [label="Generate certificate"] SecretManager -> cfiles [label="Write certs to file"] cfiles [label="Certificate Files"] grpc [shape=diamond] } subgraph cluster_istiod {...

These are replaced by this chart.
While not required, it is recommended all new users use this chart, and existing users migrate when possible.

This chart has the following benefits and differences:
* Designed with Helm best practices in mind (standardized values options, values schema, values are not all nested under `gateways.istio-ingressgateway.*`, release name and namespace taken into account, etc).

    container_kubeconfig+="/config/${kubeconfig_random}:"
    CONDITIONAL_HOST_MOUNTS+="--mount type=bind,source=${local_config},destination=/config/${kubeconfig_random} "
  fi
}

# This function is designed for maximum compatibility with various platforms. This runs on
# any Mac or Linux platform with bash 4.2+. Please take care not to modify this function
# without testing properly.
#

This document provides an overview of the architecture and design decisions around Ztunnel, the node-proxy component in ambient mode.

## Background and motivation

Motivations to implement ztunnel generally came from two areas.

First, and most importantly, it serves as a means to implement the real goal: waypoints.