Istio on GKE

Istio on GKE is an add-on for GKE that lets you quickly create a cluster with all the components you need to create and run an Istio service mesh, in a single step. Once installed, your Istio control plane components are automatically kept up-to-date, with no need for you to worry about upgrading to new versions. You can also use the add-on to install Istio on an existing cluster.

What is Istio?

Istio is an open service mesh that provides a uniform way to connect, manage, and secure microservices. It supports managing traffic flows between services, enforcing access policies, and aggregating telemetry data, all without requiring changes to the microservice code.

Istio gives you:

  • Automatic load balancing for HTTP, gRPC, WebSocket, MongoDB, and TCP traffic.
  • Fine-grained control of traffic behavior with rich routing rules, retries, failovers, and fault injection.
  • A configurable policy layer and API supporting access controls, rate limits, and quotas.
  • Automatic metrics, logs, and traces for all traffic within a cluster, including cluster ingress, and egress.
  • Secure service-to-service communication in a cluster with strong identity based authentication and authorization.

You configure Istio access control, routing rules, and so on using a custom Kubernetes API, either via kubectl or the Istio command line tool istioctl, which provides extra validation.

You can find out much more about Istio in our overview and read the full open source documentation set at istio.io.

What is Istio on GKE?

Istio on GKE is a tool that provides automated installation and upgrade of Istio in your GKE cluster. When you upgrade GKE, the add-on is automatically upgraded to the most recent GKE-supported version of Istio This lets you easily manage the installation and upgrade of Istio as part of the GKE cluster lifecycle.

It is important to note that, when using Istio on GKE, Istio will be running inside your cluster. There is no service level agreement (SLA) on the Istio components running in your cluster.

Should I use Istio on GKE?

While Istio on GKE does manage installation and upgrade, it uses default installation options for the control plane that are suited for most needs. However, you should be aware of these limitations:

  • The version of Istio installed is tied to the GKE version, and you will not be able to update them independently.

  • There are strong limitations over the configuration of the control plane. You should review these limitations before using the Istio on GKE add-on in production.

If you need to use a more recent open source version of Istio, or want greater control over your Istio control plane configuration (which may happen in some production use cases), we recommend that you use the open source version of Istio rather than the Istio on GKE add-on. You can find instructions for installing open source Istio on GKE in Installing Istio on a GKE cluster.

If you no longer want to use our automatic installation functionality for whatever reason, you can uninstall the add-on. You can find out how to do this in Uninstalling Istio on GKE.

What's installed?

When you create or update a cluster with Istio on GKE, the following core Istio components are installed:

  • Pilot, which is responsible for service discovery and for configuring the Envoy sidecar proxies to manage your service mesh's traffic.
  • The Mixer components Istio-Policy and Istio-Telemetry, which enforce usage policies and gather telemetry data across the service mesh.
  • The Istio ingress gateway, which provides an ingress point for traffic from outside the cluster.
  • (Istio 1.0 versions only) The Istio egress gateway, which allows Istio features like monitoring and routing rules to be applied to traffic exiting the mesh. The Istio egress gateway isn't installed by default in version 1.1 and later.
  • Citadel, which automates key and certificate management for Istio.
  • Galley, which provides configuration management services for Istio.

The installation also lets you add the Istio sidecar proxy to your service workloads, allowing them to communicate with the control plane and join the Istio mesh.

You can find out more about installing and uninstalling the add-on and your installation options in Installing Istio on GKE.

Stackdriver support

For clusters with Stackdriver Kubernetes Engine Monitoring enabled, the Istio Stackdriver adapter is installed along with the core components described above. The adapter can send metrics, logging, and trace data from your mesh to Stackdriver, providing observability into your services' behavior in the Google Cloud Console and Stackdriver console. Once you've enabled a particular Stackdriver feature for your project and cluster, that data is sent from your mesh by default. Note that the Istio on GKE add-on automatically sets the access scopes in the cluster's node pool for Stackdriver Monitoring, Logging, and Trace. You can find more details about working with Stackdriver in its documentation.

Monitoring

If the Stackdriver Monitoring API is enabled in your Google Cloud project, your Istio mesh will automatically send metrics related to your services (such as the number of bytes received by a particular service) to Stackdriver, where they will appear in the Metrics Explorer. You can use these metrics to create custom dashboards and alerts, letting you monitor your services over time and receive alerts when, for example, a service is nearing a specified number of requests. You can also combine these metrics using filters and aggregations with Stackdriver's built-in metrics to get new insights into your service behavior.

To go to Metrics Explorer, do the following:

  1. In the Google Cloud Console, select Monitoring, or use the following button:

    Go to Monitoring

  2. Select Resources > Metrics Explorer.

For a full list of Istio metrics, see the Stackdriver Monitoring documentation.

Logging

If the Stackdriver Logging API is enabled in your Google Cloud project, your Istio mesh will automatically send logs to Stackdriver, where they will appear in the logs viewer. See the Stackdriver Logging documentation to find out more about what you can do with the log data, such as exporting logs to BigQuery.

Tracing

You can enable Stackdriver Trace so that your Istio mesh automatically sends trace data to Stackdriver, where it appears in the trace viewer. Note that to get the most from distributed tracing to help find performance bottlenecks, you will need to change your workloads to instrument tracing headers. You can find out how to do this in the Istio Distributed Tracing guide.

How does the upgrade process work?

The Istio lifecycle is managed as a part of the GKE upgrade process. In GKE, there are two upgrade processes:

  • Master upgrade: The master upgrade process is automatic and updates the Kubernetes control plane components (API server, scheduler, controller manager, and so on) on the master node as well as the add-ons. The Istio control plane components upgrade is managed as a part of this process.
  • Node upgrade: The node upgrade process can be either automatic (opt-in; recommended) or manual, which updates the Kubernetes components on the worker nodes to sync with the same version of the master node. The Istio sidecar upgrade is managed as a part of this process.

Istio on GKE automatically upgrades the control plane to a recent (not necessarily latest) stable version. The version is selected based on observed stability and performance in open source deployments over a period of time. Version upgrades are announced in advance on the istio-gke-announce group. In general, version upgrades are rolled out gradually to all GKE versions over a period of two or more weeks, starting with the most recent version.

Control plane versions are tested for backwards compatibility with the last two prior data plane (sidecar proxy) versions. Once you have upgraded your GKE cluster, we recommend that you update the sidecars to the current control plane version as soon as possible, either by restarting pods (with auto-inject enabled) or manually re-injecting the appropriate version.

Istio on GKE does not allow user control of the control plane version.

Modifying control plane settings

Because Istio on GKE controls how your control plane is installed and upgraded, it does not let you edit most of the control plane configuration settings provided in our installation. You can see the default install options in the manifests for your labelled Istio on GKE version (the manifest that's applied depends on your chosen mTLS mode and Stackdriver settings). For example, you can find the install options for version 1.0.3-gke.3 in the console under storage/browser/gke-release/istio/release/1.0.3-gke.3/manifests/. Any edits to these options, other than the settings specified below, will be reverted by the Kubernetes add-on manager. Non-editable options are reverted every minute.

The settings you can (and, for production installations, should) configure while using the add-on are:

  • Horizontal scaling for control plane components, either using autoscaling or by manually setting the number of replicas.
  • Resource requests for control plane containers.
  • Pod disruption budgets for deployments you need to remain available during upgrades, such as the provided Istio ingress gateway.

You can find out how to configure these settings in Configuring your control plane.

In each case the settings you specify are retained when your installation is upgraded by the add-on.

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