# Istio

## Upgrade Istio Manifests

Istio ships with an installer called `istioctl`, which is a deployment /
debugging / configuration management tool for Istio all in one package.
In this section, we explain how to upgrade our istio kustomize packages
by leveraging `istioctl`. Assuming the new version is `X.Y.Z` and the
old version is `X1.Y1.Z1`:

1. Make a copy of the old istio manifests tree, which will become the
    kustomization for the new Istio version:

        export MANIFESTS_SRC=<path/to/manifests/repo>
        export ISTIO_OLD=$MANIFESTS_SRC/common/istio-X1-Y1
        export ISTIO_NEW=$MANIFESTS_SRC/common/istio-X-Y
        cp -a $ISTIO_OLD $ISTIO_NEW

2. Download `istioctl` for version `X.Y.Z`:

        $ ISTIO_VERSION="X.Y.Z"
        $ wget "https://github.com/istio/istio/releases/download/${ISTIO_VERSION}/istio-${ISTIO_VERSION}-linux-amd64.tar.gz"
        $ tar xvfz istio-${ISTIO_VERSION}-linux-amd64.tar.gz
        # sudo mv istio-${ISTIO_VERSION}/bin/istioctl /usr/local/bin/istioctl

3. Generate manifests and add them to their respective packages. We
    will generate manifests using `istioctl`, the
    `profile.yaml` file from upstream and the
    `profile-overlay.yaml` file that contains our desired
    changes:

        export PATH="$MANIFESTS_SRC/scripts:$PATH"
        cd $ISTIO_NEW
        istioctl manifest generate --cluster-specific -f profile.yaml -f profile-overlay.yaml > dump.yaml
        ./split-istio-packages -f dump.yaml
        mv $ISTIO_NEW/crd.yaml $ISTIO_NEW/istio-crds/base
        mv $ISTIO_NEW/install.yaml $ISTIO_NEW/istio-install/base
        mv $ISTIO_NEW/cluster-local-gateway.yaml $ISTIO_NEW/cluster-local-gateway/base
        rm dump.yaml

    ---
    **NOTE**

    `split-istio-packages` is a python script in the same folder as this file.
    The `ruamel.yaml` version used is 0.16.12.

    `--cluster-specific` is a flag that determines if a current K8s cluster context will be used to dynamically detect default settings. Ensure you have a target cluster ready before running the above commands.
    We target Kubernetes 1.32+ for compatibility. The `--cluster-specific` flag helps ensure generated resources are compatible with your cluster version and configuration.

    ---

## Changes to Istio's upstream manifests

### Changes to the upstream IstioOperator profile

Changes to Istio's upstream profile `default` are the following:

- Add a `cluster-local-gateway` component for Kserve. Knative-local-gateway is now obsolete <https://github.com/kubeflow/manifests/pull/2355/commits/adc00b804404ea08685a044ae595be0bed9adb59>.
- Disable the EgressGateway component. We do not use it and it adds unnecessary complexity.

These changes are captured in the [profile-overlay.yaml](profile-overlay.yaml) file.

### Changes to the upstream manifests using kustomize

The Istio kustomizations make the following changes:

- Remove PodDisruptionBudget from `istio-install` and `cluster-local-gateway` kustomizations. See:
  - <https://github.com/istio/istio/issues/12602>
  - <https://github.com/istio/istio/issues/24000>
- Add Istio AuthorizationPolicy to allow all requests to the Istio Ingressgateway and the Istio cluster-local gateway.
- Add Istio AuthorizationPolicy in Istio's root namespace, so that sidecars deny traffic by default (explicit deny-by-default authorization model).
- Add Gateway CRs for the Istio Ingressgateway and the Istio cluster-local gateway, as `istioctl` stopped generating them in later versions.
- Add the istio-system namespace object to `istio-namespace`, as `istioctl` stopped generating it in later versions.
- Configure TCP KeepAlives.
- Disable tracing as it causes DNS breakdown. See:
  <https://github.com/istio/istio/issues/29898>
- Set ENABLE_DEBUG_ON_HTTP=false according to <https://istio.io/latest/docs/ops/best-practices/security/#control-plane>
