Installing the Sidecar

    The following sections describe two ways of injecting the Istio sidecar into a pod: manually using the command or by enabling automatic Istio sidecar injection in the pod’s namespace.

    Manual injection directly modifies configuration, like deployments, and injects the proxy configuration into it.

    When enabled in a pod’s namespace, automatic injection injects the proxy configuration at pod creation time using an admission controller.

    Injection occurs by applying a template defined in the istio-sidecar-injector ConfigMap.

    To manually inject a deployment, use :

    Zip

    By default, this will use the in-cluster configuration. Alternatively, injection can be done using local copies of the configuration.

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

    Run kube-inject over the input file and deploy.

    1. $ istioctl kube-inject \
    2.     --injectConfigFile inject-config.yaml \
    3.     --meshConfigFile mesh-config.yaml \
    4.     --valuesFile inject-values.yaml \
    5.     --filename @samples/sleep/sleep.yaml@ \
    6.     | kubectl apply -f -

    Verify that the sidecar has been injected into the sleep pod with 2/2 under the READY column.

    1. $ kubectl get pod  -l app=sleep
    2. NAME                     READY   STATUS    RESTARTS   AGE
    3. sleep-64c6f57bc8-f5n4x   2/2     Running   0          24s

    Sidecars can be automatically added to applicable Kubernetes pods using a mutating webhook admission controller provided by Istio.

    While admission controllers are enabled by default, some Kubernetes distributions may disable them. If this is the case, follow the instructions to .

    When you set the istio-injection=enabled label on a namespace and the injection webhook is enabled, any new pods that are created in that namespace will automatically have a sidecar added to them.

    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.

    Deploying an app

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

    1. $ kubectl apply -f @samples/sleep/sleep.yaml@
    2. $ kubectl get deployment -o wide
    3. NAME      DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE       CONTAINERS   IMAGES       SELECTOR
    4. sleep     1         1         1            1           12m       sleep        tutum/curl   app=sleep
    1. $ kubectl get pod
    2. NAME                     READY     STATUS        RESTARTS   AGE
    3. sleep-776b7bcdcd-7hpnk   1/1       Running       0          4

    Label the default namespace with istio-injection=enabled

    1. $ kubectl delete pod -l app=sleep
    2. $ kubectl get pod -l app=sleep
    3. NAME                     READY     STATUS        RESTARTS   AGE
    4. sleep-776b7bcdcd-7hpnk   1/1       Terminating   0          1m
    5. 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.

    1. $ kubectl describe pod -l app=sleep

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

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

    Understanding what happened

    When Kubernetes invokes the webhook, the configuration is applied. The default configuration injects the sidecar into pods in any namespace with the istio-injection=enabled label. The istio-sidecar-injector configuration map specifies the configuration for the injected sidecar. To change how namespaces are selected for injection, you can edit the MutatingWebhookConfiguration with the following command:

    1. $ kubectl edit mutatingwebhookconfiguration istio-sidecar-injector

    You should restart the sidecar injector pod(s) after modifying the .

    For example, you can modify the MutatingWebhookConfiguration to always inject the sidecar into every namespace, unless a label is set. Editing this configuration is an advanced operation. Refer to the Kubernetes documentation for the MutatingWebhookConfiguration API for more information.

    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 override the default and 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 override the default and disable injection.

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

    1. apiVersion: apps/v1
    2. kind: Deployment
    3. metadata:
    4.   name: ignored
    5. spec:
    6.   template:
    7.     metadata:
    8.       annotations:
    9.         sidecar.istio.io/inject: "false"
    10.     spec:
    11.       containers:
    12.       - name: ignored
    13.         image: tutum/curl
    14.         command: ["/bin/sleep","infinity"]

    The sidecar injection template uses which, when parsed and executed, is decoded to the following struct containing the list of containers and volumes to inject into the pod.

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

    1. type SidecarTemplateData struct {
    2.     DeploymentMeta *metav1.ObjectMeta
    3.     ObjectMeta     *metav1.ObjectMeta
    4.     Spec           *corev1.PodSpec
    5.     ProxyConfig    *meshconfig.ProxyConfig  // Defined by https://istio.io/docs/reference/config/service-mesh.html#proxyconfig
    6.     MeshConfig     *meshconfig.MeshConfig   // Defined by https://istio.io/docs/reference/config/service-mesh.html#meshconfig
    7. }

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

    For example, the following template

    1. containers:
    2. - name: istio-proxy
    3.   image: istio.io/proxy:0.5.0
    4.   args:
    5.   - proxy
    6.   - sidecar
    7.   - --configPath
    8.   - {{ .ProxyConfig.ConfigPath }}
    9.   - --binaryPath
    10.   - {{ .ProxyConfig.BinaryPath }}
    12.   - {{ index .ObjectMeta.Labels "app" }}
    13.   {{ else -}}
    14.   - "istio-proxy"
    15.   {{ end -}}

    expands to

    1. containers:
    2. - name: istio-proxy
    3.   image: istio.io/proxy:0.5.0
    4.   args:
    5.   - proxy
    6.   - sidecar
    7.   - --configPath
    8.   - /etc/istio/proxy
    9.   - --binaryPath
    10.   - /usr/local/bin/envoy
    11.   - --serviceCluster
    12.   - sleep

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

    More control: adding exceptions

    There are cases where users do not have control of the pod creation, for instance, when they are created by someone else. Therefore they are unable to add the annotation sidecar.istio.io/inject in the pod, to explicitly instruct Istio whether to install the sidecar or not.

    Think of auxiliary pods that might be created as an intermediate step while deploying an application. OpenShift Source to Image Builds, for example, creates such pods for building the source code of an application. Once the binary artifact is built, the application pod is ready to run and the auxiliary pods are discarded. Those intermediate pods should not get an Istio sidecar, even if the policy is set to enabled and the namespace is properly labeled to get automatic injection.

    For such cases you can instruct Istio to not inject the sidecar on those pods, based on labels that are present in those pods. You can do this by editing the istio-sidecar-injector ConfigMap and adding the entry neverInjectSelector. It is an array of Kubernetes label selectors. They are OR'd, stopping at the first match. See an example:

    1. apiVersion: v1
    2. kind: ConfigMap
    3. metadata:
    4.   name: istio-sidecar-injector
    5. data:
    6.   config: |-
    7.     policy: enabled
    8.     neverInjectSelector:
    9.       - matchExpressions:
    10.         - {key: openshift.io/build.name, operator: Exists}
    11.       - matchExpressions:
    12.         - {key: openshift.io/deployer-pod-for.name, operator: Exists}
    13.     template: |-
    14.       initContainers:
    15. ...

    For completeness, you can also use a field called alwaysInjectSelector, with similar syntax, which will always inject the sidecar on pods that match that label selector, regardless of the global policy.

    The label selector approach gives a lot of flexibility on how to express those exceptions. Take a look at to see what you can do with them!

    It’s worth noting that annotations in the pods have higher precedence than the label selectors. If a pod is annotated with sidecar.istio.io/inject: "true/false" then it will be honored. So, the order of evaluation is:

    Pod Annotations → NeverInjectSelector → AlwaysInjectSelector → Default Policy

    Uninstalling the automatic sidecar injector

    1. $ kubectl delete mutatingwebhookconfiguration istio-sidecar-injector
    2. $ kubectl -n istio-system delete service istio-sidecar-injector
    3. $ kubectl -n istio-system delete deployment istio-sidecar-injector
    4. $ kubectl -n istio-system delete serviceaccount istio-sidecar-injector-service-account

    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.

    See also

    Pods and Services

    Prepare your Kubernetes pods and services to run in an Istio-enabled cluster.

    De-mystify how Istio manages to plugin its data-plane components into an existing deployment.

    Install Istio with the Istio CNI plugin

    Install and use Istio with the Istio CNI plugin, allowing operators to deploy services with lower privilege.

    A mechanism to acquire and share an application certificate and key through mounted files.

    DNS Certificate Management

    Provision and manage DNS certificates in Istio.