Installing the sidecar

Injection

Each pod in the mesh must be running an Istio compatible sidecar.

The following sections describe two ways of injecting the Istio sidecar into a pod: manually using the istioctl CLI tool or automatically using the Istio sidecar injector.

Manual injection modifies the controller configuration, e.g. deployment. It does this by modifying the pod template spec such that all pods for that deployment are created with the injected sidecar. Adding/Updating/Removing the sidecar requires modifying the entire deployment.

Automatic injection injects at pod creation time. The controller resource is unmodified. Sidecars can be updated selectively by manually deleting a pods or systematically with a deployment rolling update.

Manual and automatic injection both use the configuration from the istio-sidecar-injector and istio ConfigMaps in the istio-system namespace. Manual injection can also optionally load configuration from local files.

Manual sidecar injection

Inject the sidecar into the deployment using the in-cluster configuration.

$ istioctl kube-inject -f @samples/sleep/sleep.yaml@ | kubectl apply -f -

Alternatively, inject using local copies of the configuration.

The istioctl kube-inject operation may not be repeated on the output from a previous kube-inject. The kube-inject operation is not idempotent. For upgrade purposes, if using manual injection, it is recommended to keep the original non-injected yaml file so that the data plane sidecars may be updated.

$ kubectl -n istio-system get configmap istio-sidecar-injector -o=jsonpath='{.data.config}' > inject-config.yaml
$ kubectl -n istio-system get configmap istio -o=jsonpath='{.data.mesh}' > mesh-config.yaml

Run kube-inject over the input file and deploy.

$ istioctl kube-inject \
    --injectConfigFile inject-config.yaml \
    --meshConfigFile mesh-config.yaml \
    --filename @samples/sleep/sleep.yaml@ \
    --output sleep-injected.yaml
$ kubectl apply -f sleep-injected.yaml

Verify that the sidecar has been injected into the deployment.

$ kubectl get deployment sleep -o wide
NAME      DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE       CONTAINERS          IMAGES                             SELECTOR
sleep     1         1         1            1           2h        sleep,istio-proxy   tutum/curl,unknown/proxy:unknown   app=sleep

Automatic sidecar injection

Sidecars can be automatically added to applicable Kubernetes pods using a mutating webhook admission controller. This feature requires Kubernetes 1.9 or later. Verify that the kube-apiserver process has the admission-control flag set with the MutatingAdmissionWebhook and ValidatingAdmissionWebhook admission controllers added and listed in the correct order and the admissionregistration API is enabled.

$ kubectl api-versions | grep admissionregistration
admissionregistration.k8s.io/v1alpha1
admissionregistration.k8s.io/v1beta1

See Kubernetes quick start for instructions on installing Kubernetes version >= 1.9.

Note that unlike manual injection, automatic injection occurs at the pod-level. You won't see any change to the deployment itself. Instead you'll want to check individual pods (via kubectl describe) to see the injected proxy.

Disabling or updating the webhook

The sidecar injecting webhook is enabled by default. If you wish to disable the webhook, you can use Helm to generate an updated istio.yaml with the option sidecarInjectorWebhook.enabled set to false. E.g.

$ helm template --namespace=istio-system --set sidecarInjectorWebhook.enabled=false install/kubernetes/helm/istio > istio.yaml
$ kubectl create ns istio-system
$ kubectl apply -n istio-system -f istio.yaml

In addition, there are some other configuration parameters defined for the sidecar injector webhook service in values.yaml. You can override the default values to customize the installation.

Deploying an app

Deploy sleep app. Verify both deployment and pod have a single container.

$ kubectl apply -f @samples/sleep/sleep.yaml@
$ kubectl get deployment -o wide
NAME      DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE       CONTAINERS   IMAGES       SELECTOR
sleep     1         1         1            1           12m       sleep        tutum/curl   app=sleep

$ kubectl get pod
NAME                     READY     STATUS        RESTARTS   AGE
sleep-776b7bcdcd-7hpnk   1/1       Running       0          4

Label the default namespace with istio-injection=enabled

$ kubectl label namespace default istio-injection=enabled
$ kubectl get namespace -L istio-injection
NAME           STATUS    AGE       ISTIO-INJECTION
default        Active    1h        enabled
istio-system   Active    1h
kube-public    Active    1h
kube-system    Active    1h

Injection occurs at pod creation time. Kill the running pod and verify a new pod is created with the injected sidecar. The original pod has 1/1 READY containers and the pod with injected sidecar has 2/2 READY containers.

$ kubectl delete pod sleep-776b7bcdcd-7hpnk
$ kubectl get pod
NAME                     READY     STATUS        RESTARTS   AGE
sleep-776b7bcdcd-7hpnk   1/1       Terminating   0          1m
sleep-776b7bcdcd-bhn9m   2/2       Running       0          7s

View detailed state of the injected pod. You should see the injected istio-proxy container and corresponding volumes. Be sure to substitute the correct name for the Running pod below.

$ kubectl describe pod sleep-776b7bcdcd-bhn9m

Disable injection for the default namespace and verify new pods are created without the sidecar.

$ kubectl label namespace default istio-injection-
$ kubectl delete pod sleep-776b7bcdcd-bhn9m
$ kubectl get pod
NAME                     READY     STATUS        RESTARTS   AGE
sleep-776b7bcdcd-bhn9m   2/2       Terminating   0          2m
sleep-776b7bcdcd-gmvnr   1/1       Running       0          2s

Understanding what happened

admissionregistration.k8s.io/v1beta1#MutatingWebhookConfiguration configures when the webhook is invoked by Kubernetes. The default supplied with Istio selects pods in namespaces with label istio-injection=enabled. The set of namespaces in which injection is applied can be changed by editing the MutatingWebhookConfiguration with kubectl edit mutatingwebhookconfiguration istio-sidecar-injector.

The sidecar injector pod(s) should be restarted after modifying the mutatingwebhookconfiguration.

The istio-sidecar-injector ConfigMap in the istio-system namespace has the default injection policy and sidecar injection template.

policy

disabled - The sidecar injector will not inject the sidecar into pods by default. Add the sidecar.istio.io/inject annotation with value true to the pod template spec to enable injection.

enabled - The sidecar injector will inject the sidecar into pods by default. Add the sidecar.istio.io/inject annotation with value false to the pod template spec to disable injection.

The following example uses the sidecar.istio.io/inject annotation to disable sidecar injection.

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: ignored
spec:
  template:
    metadata:
      annotations:
        sidecar.istio.io/inject: "false"
    spec:
      containers:
      - name: ignored
        image: tutum/curl
        command: ["/bin/sleep","infinity"]

template

The sidecar injection template uses https://golang.org/pkg/text/template which, when parsed and executed, is decoded to the following struct containing the list of containers and volumes to inject into the pod.

type SidecarInjectionSpec struct {
      InitContainers   []v1.Container `yaml:"initContainers"`
      Containers       []v1.Container `yaml:"containers"`
      Volumes          []v1.Volume    `yaml:"volumes"`
      ImagePullSecrets []corev1.LocalObjectReference `yaml:"imagePullSecrets"`
}

The template is applied to the following data structure at runtime.

type SidecarTemplateData struct {
    ObjectMeta  *metav1.ObjectMeta
    Spec        *v1.PodSpec
    ProxyConfig *meshconfig.ProxyConfig  // Defined by https://istio.io/docs/reference/config/service-mesh.html#proxyconfig
    MeshConfig  *meshconfig.MeshConfig   // Defined by https://istio.io/docs/reference/config/service-mesh.html#meshconfig
}

ObjectMeta and Spec are from the pod. ProxyConfig and MeshConfig are from the istio ConfigMap in the istio-system namespace. Templates can conditional define injected containers and volumes with this data.

For example, the following template snippet from install/kubernetes/istio-sidecar-injector-configmap-release.yaml

containers:
- name: istio-proxy
  image: istio.io/proxy:0.5.0
  args:
  - proxy
  - sidecar
  - --configPath
  - {{ .ProxyConfig.ConfigPath }}
  - --binaryPath
  - {{ .ProxyConfig.BinaryPath }}
  - --serviceCluster
  {{ if ne "" (index .ObjectMeta.Labels "app") -}}
  - {{ index .ObjectMeta.Labels "app" }}
  {{ else -}}
  - "istio-proxy"
  {{ end -}}

expands to

containers:
- name: istio-proxy
  image: istio.io/proxy:0.5.0
  args:
  - proxy
  - sidecar
  - --configPath
  - /etc/istio/proxy
  - --binaryPath
  - /usr/local/bin/envoy
  - --serviceCluster
  - sleep

when applied over a pod defined by the pod template spec in samples/sleep/sleep.yaml

Uninstalling the automatic sidecar injector

$ kubectl delete mutatingwebhookconfiguration istio-sidecar-injector
$ kubectl -n istio-system delete service istio-sidecar-injector
$ kubectl -n istio-system delete deployment istio-sidecar-injector
$ kubectl -n istio-system delete serviceaccount istio-sidecar-injector-service-account
$ kubectl delete clusterrole istio-sidecar-injector-istio-system
$ kubectl delete clusterrolebinding istio-sidecar-injector-admin-role-binding-istio-system

The above command will not remove the injected sidecars from Pods. A rolling update or simply deleting the pods and forcing the deployment to create them is required.

Optionally, it may also be desirable to clean-up other resources that were modified in this task.

$ kubectl label namespace default istio-injection-