Kyma Service Mesh is the component responsible for service-to-service communication, proxying, service discovery, traceability, and security. To deliver this functionality, Kyma Service Mesh uses Istio open platform.

The main principle of Kyma Service Mesh is to inject Pods of every service with the Envoy sidecar proxy. Envoy intercepts the communication between the services and regulates it by applying and enforcing the rules you create. Kyma Dex, which is also a part of the Service Mesh, allows you to integrate any OpenID Connect-compliant identity provider or a SAML2-based enterprise authentication server with your solution.

By default, Istio in Kyma has mutual TLS (mTLS) enabled and injects a sidecar container to every Pod. You can manage mTLS traffic in services or at a Namespace level by creating Destination Rules and Peer Authentications. If you disable sidecar injection in a service or in a Namespace, you must manage their traffic configuration by creating appropriate Destination Rules and Peer Authentications.

NOTE: The Istio Control Plane doesn't have mTLS enabled.

NOTE: For security and performance we use the distroless version of Istio images. Those images are not Debian-based and are slimmed down to reduce any potential attack surface and increase startup time.

As a core component, Istio is installed with every Kyma deployment by default. The installation includes the following steps:

1. Istio is installed using the istioctl tool. The installation resources reside in the resources/istio directory.

2. A custom Istio Patch job runs and checks if the detected Istio deployment meets the following criteria:

• A specific version of Istio is installed. The required version is defined in the values file.
• Mutual TLS (mTLS) policy is enabled and set to strict.
• Automatic sidecar injection is enabled.

If the Istio deployment fails to meet any of these criteria, the patch fails, which results in a failed installation. In such case, get the Istio Patch logs to find out which criteria the Istio deployment didn't meet. Run:

kubectl logs -n istio-system -l app=istio-kyma-patch

NOTE: The Istio patch component is enabled by default, but you can disable it at any time using the instructions.

Use an existing Istio installation with Kyma

You can use an existing installation of Istio with your Kyma installation. To use it:

• Make sure Istio is already running in the cluster.
• Don't disable the Istio Patch component.
• Install Kyma without Istio. Read the configuration document for more details.

By default, istiod watches all Pod creation operations on all Namespaces and injects the newly created Pods with a sidecar proxy.

You can disable sidecar proxy injection for either an entire Namespace or a single Deployment.

• To disable sidecar proxy injection for a Namespace, set the istio-injection label value to disabled for the Namespace in which you want to disable the sidecar proxy injection. Use this command: kubectl label namespace {YOUR_NAMESPACE} istio-injection=disabled
• To disable sidecar proxy injection for a Deployment, add this annotation to the Deployment configuration file: sidecar.istio.io/inject: "false"

Read the Istio documentation to learn more about sidecar proxy injection.

By default, every Kyma deployment is installed with the Service Mesh provider Istio, using what is considered a development profile. In this case, this means that:

• Horizontal Pod Autoscaler (HPA) is enabled for all components, with the default number for replicas.
• All components have severely reduced resource quotas, which is a performance factor.

This configuration is not considered production-ready. To use the Kyma Service Mesh in a production environment, configure Istio to use the production profile.

Production profile

The production profile introduces the following changes to the Istio Service Mesh:

• Resource quotas for all Istio components are increased.
• All Istio components have HPA enabled.
• HPA for Istio Ingress Gateway has been customized:
  • Minimum number of replicas: 3
  • Maximum number of replicas: 10

System requirements

As the production profile is configured with increased performance it mind, the recommend system setup is different:

Use the production profile

You can deploy a Kyma cluster with Istio configured to use the production profile, or configure Istio in a running cluster to use the production profile. Follow these steps:

TIP: Read the Istio custom configuration section to learn how to provide your own overrides.

The 503 status code received when you try to access the Console UI or any other endpoint in Kyma can be caused by a configuration error in the Istio Ingress Gateway. As a result, the endpoint you call is not exposed. To fix this problem, restart the Pods of the Gateway.

1. List all available endpoints:

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   kubectl get virtualservice --all-namespaces

2. Restart the Pods of the Istio Ingress Gateway to force them to recreate their configuration:

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   kubectl delete pod -l app=istio-ingressgateway -n istio-system

If this solution doesn't work, you need to change the image of the Istio Ingress Gateway to allow further investigation. Kyma uses distroless Istio images which are more secure, but you cannot execute commands inside them. Follow this steps:

1. Edit the Istio Ingress Gateway Deployment:

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   kubectl edit deployment -n istio-system istio-ingressgateway

2. Find the istio-proxy container and delete the -distroless suffix.

3. Check all ports used by the Istio Ingress Gateway:

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   kubectl exec -ti -n istio-system $(kubectl get pod -l app=istio-ingressgateway -n istio-system -o name) -c istio-proxy -- netstat -lptnu

4. If ports 80 and 443 are not used, check the logs of the Istio Ingress Gateway container for errors related to certificates. Run:

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   kubectl logs -n istio-system -l app=istio-ingressgateway -c ingress-sds

5. In case of certificate-related issues, make sure kyma-gateway-certs and app-connector-certs Secrets are available in the istio-system Namespace and that they contain proper data. Run:

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   kubectl get secrets -n istio-system kyma-gateway-certs -oyaml
   kubectl get secrets -n istio-system app-connector-certs -oyaml

6. To regenerate a corrupted certificate, follow this tutorial. If you are running Kyma provisioned through Gardener, follow this tutorial instead.

   NOTE: Remember to switch back to the distroless image after you resolved the issue.

Mutual TLS (mTLS) is enabled in the Service Mesh by default. As a result, every element of the Service Mesh must have an Istio sidecar with a valid TLS certificate to allow communication. Attempts to establish connection between a service without a sidecar and a service with a sidecar result in a Connection reset by peer or a GOAWAY response.

• To enable sidecar injection for Pods of existing Services, restart them after upgrading Kyma.
• To whitelist a Service without a sidecar and disable mTLS traffic for it, create a DestinationRule.

• To allow connections between Services without a sidecar and a Service with a sidecar, create a Peer Authentication in the PERMISSIVE mode.

  NOTE: In Istio 1.5, Peer Authentication replaces the deprecated Authentication Policy.

Kyma has sidecar injection enabled by default - a sidecar is injected to every Pod in a cluster without the need to add any labels. For more information, read this document. If a Pod doesn't have a sidecar and you did not disable sidecar injection on purpose, follow these steps to troubleshoot:

1. Check if sidecar injection is disabled in the Namespace of the Pod. Run this command to check the istio-injection label:

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   kubectl get namespaces {NAMESPACE} -o jsonpath='{ .metadata.labels.istio-injection }'

   If the command returns disabled the sidecar injection is disabled in this Namespace. To add a sidecar to the Pod, move the Pod's deployment to a Namespace that has sidecar injection enabled, or remove the label from the Namespace and restart the Pod.

   WARNING: Removing the istio-injection=disabled label from Namespace results in injecting sidecars to all Pods inside of the Namespace.

2. Check if sidecar injection is disabled in the Pod's Deployment:

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   kubectl get deployments {DEPLOYMENT_NAME} -n {NAMESPACE} -o jsonpath='{ .spec.template.metadata.annotations }'

   Sidecar injection is disabled if the output contains the sidecar.istio.io/inject:false line. Delete the label and restart the Pod to enable sidecar injection for the Deployment.

For more information, read this document or follow the Istio documentation.

Kyma has sidecar injection enabled by default - a sidecar is injected to every Pod in a cluster without the need to add any labels. For more information, read this document.

The sidecar version in Pods must match the installed Istio version. Otherwise, mesh connectivity may be broken. This issue may appear during Kyma upgrade. When Kyma is upgraded to a new version along with a new Istio version, existing sidecars injected into Pods remain in an original version. Kyma contains the istio-proxy-reset job that performs a rollout for most common workload types, such as Deployments, DaemonSets, etc. The job ensures all Kyma components are properly updated. However, some user-defined workloads can't be rolled out automatically. This applies, for example, to a standalone Pod without any backing management mechanism, such as a ReplicaSet or a Job. Such user-defined workloads, that are not part of Kyma, must be manually restarted to work correctly with the updated Istio version.

To check if any Pods or workloads require a manual restart, follow these steps:

1. Check the installed Istio version using one of these methods:

   • From the istiod deployment in a running cluster:

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     export KYMA_ISTIO_VERSION=$(kubectl get deployment istiod -n istio-system -o json | jq '.spec.template.spec.containers | .[].image' | sed 's/[^:"]*[:]//' | sed 's/["]//g')

   • From Kyma sources - run this command from within the directory that contains Kyma sources:

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     export KYMA_ISTIO_VERSION=$(cat resources/istio/Chart.yaml | grep version | sed 's/[^:]*[:]//' | sed 's/ //g')

2. Get the list of objects which require rollout using one of these methods:

   • Find all Pods with outdated sidecars. The returned list follows the name/namespace format. The empty output means that there is no Pod that requires migration. To find all outdated Pods, run:
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     COMMON_ISTIO_PROXY_IMAGE_PREFIX="eu.gcr.io/kyma-project/external/istio/proxyv2"
     kubectl get pods -A -o json | jq -rc '.items | .[] | select(.spec.containers[].image | startswith("'"${COMMON_ISTIO_PROXY_IMAGE_PREFIX}"'") and (endswith("'"${KYMA_ISTIO_VERSION}"'") | not))  | "\(.metadata.name)/\(.metadata.namespace)"'

* Run the `istio-proxy-reset` script in the dry-run mode. The output contains information about objects, such as Pods, Deployments, etc., that require rollout. To run the script, run this command from within the directory with checked-out Kyma sources:
    ```bash
    EXPECTED_ISTIO_PROXY_IMAGE="${KYMA_ISTIO_VERSION}"
    COMMON_ISTIO_PROXY_IMAGE_PREFIX="eu.gcr.io/kyma-project/external/istio/proxyv2"
    DRY_RUN="true"
    ./resources/istio/files/istio-proxy-reset.sh
    ```

After you find a set of objects that require the manual update, restart their related workloads so that new Istio sidecars are injected into the Pods.