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Service Mesh and Istio differences - Service Mesh 1.x | Service Mesh | OpenShift Container Platform 4.5
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Service Mesh and Istio differences

An installation of Red Hat OpenShift Service Mesh differs from upstream Istio community installations in multiple ways. The modifications to Red Hat OpenShift Service Mesh are sometimes necessary to resolve issues, provide additional features, or to handle differences when deploying on OpenShift Container Platform.

The current release of Red Hat OpenShift Service Mesh differs from the current upstream Istio community release in the following ways:

Red Hat OpenShift Service Mesh multitenant installation

Whereas upstream Istio takes a single tenant approach, Red Hat OpenShift Service Mesh supports multiple independent control planes within the cluster. Red Hat OpenShift Service Mesh uses a multitenant operator to manage the control plane lifecycle.

Red Hat OpenShift Service Mesh installs a multitenant control plane by default. You specify the projects that can access the Service Mesh, and isolate the Service Mesh from other control plane instances.

Multitenancy versus cluster-wide installations

The main difference between a multitenant installation and a cluster-wide installation is the scope of privileges used by the control plane deployments, for example, Galley and Pilot. The components no longer use cluster-scoped Role Based Access Control (RBAC) resource ClusterRoleBinding.

Every project in the ServiceMeshMemberRoll members list will have a RoleBinding for each service account associated with the control plane deployment and each control plane deployment will only watch those member projects. Each member project has a maistra.io/member-of label added to it, where the member-of value is the project containing the control plane installation.

Red Hat OpenShift Service Mesh configures each member project to ensure network access between itself, the control plane, and other member projects. The exact configuration differs depending on how OpenShift software-defined networking (SDN) is configured. See About OpenShift SDN for additional details.

If the OpenShift Container Platform cluster is configured to use the SDN plug-in:

  • NetworkPolicy: Red Hat OpenShift Service Mesh creates a NetworkPolicy resource in each member project allowing ingress to all pods from the other members and the control plane. If you remove a member from Service Mesh, this NetworkPolicy resource is deleted from the project.

    This also restricts ingress to only member projects. If you require ingress from non-member projects, you need to create a NetworkPolicy to allow that traffic through.

  • Multitenant: Red Hat OpenShift Service Mesh joins the NetNamespace for each member project to the NetNamespace of the control plane project (the equivalent of running oc adm pod-network join-projects --to control-plane-project member-project). If you remove a member from the Service Mesh, its NetNamespace is isolated from the control plane (the equivalent of running oc adm pod-network isolate-projects member-project).

  • Subnet: No additional configuration is performed.

Cluster scoped resources

Upstream Istio has two cluster scoped resources that it relies on. The MeshPolicy and the ClusterRbacConfig. These are not compatible with a multitenant cluster and have been replaced as described below.

  • ServiceMeshPolicy replaces MeshPolicy for configuration of control-plane-wide authentication policies. This must be created in the same project as the control plane.

  • ServicemeshRbacConfig replaces ClusterRbacConfig for configuration of control-plane-wide role based access control. This must be created in the same project as the control plane.

Differences between Istio and Red Hat OpenShift Service Mesh

An installation of Red Hat OpenShift Service Mesh differs from an installation of Istio in multiple ways. The modifications to Red Hat OpenShift Service Mesh are sometimes necessary to resolve issues, provide additional features, or to handle differences when deploying on OpenShift.

Command line tool

The command line tool for Red Hat OpenShift Service Mesh is oc.  Red Hat OpenShift Service Mesh  does not support istioctl.

Automatic injection

The upstream Istio community installation automatically injects the sidecar into pods within the projects you have labeled.

Red Hat OpenShift Service Mesh does not automatically inject the sidecar to any pods, but requires you to opt in to injection using an annotation without labeling projects. This method requires fewer privileges and does not conflict with other OpenShift capabilities such as builder pods. To enable automatic injection you specify the sidecar.istio.io/inject annotation as described in the Automatic sidecar injection section.

Istio Role Based Access Control features

Istio Role Based Access Control (RBAC) provides a mechanism you can use to control access to a service. You can identify subjects by user name or by specifying a set of properties and apply access controls accordingly.

The upstream Istio community installation includes options to perform exact header matches, match wildcards in headers, or check for a header containing a specific prefix or suffix.

Red Hat OpenShift Service Mesh extends the ability to match request headers by using a regular expression. Specify a property key of request.regex.headers with a regular expression.

Upstream Istio community matching request headers example
apiVersion: "rbac.istio.io/v1alpha1"
kind: ServiceRoleBinding
metadata:
  name: httpbin-client-binding
  namespace: httpbin
spec:
  subjects:
  - user: "cluster.local/ns/istio-system/sa/istio-ingressgateway-service-account"
    properties:
      request.headers[<header>]: "value"
Red Hat OpenShift Service Mesh matching request headers by using regular expressions
apiVersion: "rbac.istio.io/v1alpha1"
kind: ServiceRoleBinding
metadata:
  name: httpbin-client-binding
  namespace: httpbin
spec:
  subjects:
  - user: "cluster.local/ns/istio-system/sa/istio-ingressgateway-service-account"
    properties:
      request.regex.headers[<header>]: "<regular expression>"

OpenSSL

Red Hat OpenShift Service Mesh replaces BoringSSL with OpenSSL. OpenSSL is a software library that contains an open source implementation of the Secure Sockets Layer (SSL) and Transport Layer Security (TLS) protocols. The Red Hat OpenShift Service Mesh Proxy binary dynamically links the OpenSSL libraries (libssl and libcrypto) from the underlying Red Hat Enterprise Linux operating system.

Component modifications

  • A maistra-version label has been added to all resources.

  • All ingress resources have been converted to OpenShift Route resources.

  • Grafana, Tracing (Jaeger), and Kiali are enabled by default and exposed through OpenShift routes.

  • Godebug has been removed from all templates

  • The istio-multi ServiceAccount and ClusterRoleBinding have been removed, as well as the istio-reader ClusterRole.

Envoy, Secret Discovery Service, and certificates

  • Red Hat OpenShift Service Mesh does not support QUIC-based services.

  • Deployment of TLS certificates using the Secret Discovery Service (SDS) functionality of Istio is not currently supported in Red Hat OpenShift Service Mesh. The Istio implementation depends on a nodeagent container that uses hostPath mounts.

Istio Container Network Interface (CNI) plug-in

Red Hat OpenShift Service Mesh includes CNI plug-in, which provides you with an alternate way to configure application pod networking. The CNI plug-in replaces the init-container network configuration eliminating the need to grant service accounts and projects access to Security Context Constraints (SCCs) with elevated privileges.

Routes for Istio Gateways

OpenShift routes for Istio Gateways are automatically managed in Red Hat OpenShift Service Mesh. Every time an Istio Gateway is created, updated or deleted inside the service mesh, an OpenShift route is created, updated or deleted.

A Red Hat OpenShift Service Mesh control plane component called Istio OpenShift Routing (IOR) synchronizes the gateway route. For more information see the "Automatic route creation" section.

Catch-all domains

Catch-all domains ("*") are not supported. If one is found in the Gateway definition, Red Hat OpenShift Service Mesh will create the route, but will rely on OpenShift to create a default hostname. This means that the newly created route will not be a catch all ("*") route, instead it will have a hostname in the form <route-name>[-<project>].<suffix>. Refer to the OpenShift documentation for more information about how default hostnames work and how a cluster administrator can customize it.

Subdomains

Subdomains (e.g.: "*.domain.com") are supported. However this ability doesn’t come enabled by default in OpenShift. This means that Red Hat OpenShift Service Mesh will create the route with the subdomain, but it will only be in effect if OpenShift is configured to enable it.

Transport layer security

Transport Layer Security (TLS) is supported. This means that, if the Gateway contains a tls section, the OpenShift Route will be configured to support TLS.

Kiali and service mesh

Installing Kiali via the Service Mesh on OpenShift Container Platform differs from community Kiali installations in multiple ways. These modifications are sometimes necessary to resolve issues, provide additional features, or to handle differences when deploying on OpenShift Container Platform.

  • Kiali has been enabled by default.

  • ingress has been enabled by default.

  • Updates have been made to the Kiali ConfigMap.

  • Updates have been made to the ClusterRole settings for Kiali.

  • Users should not manually edit the ConfigMap or the Kiali custom resource files as those changes might be overwritten by the Service Mesh or Kiali operators. All configuration for Kiali running on Red Hat OpenShift Service Mesh is done in the ServiceMeshControlPlane custom resource file and there are limited configuration options. Updating the operator files should be restricted to those users with cluster-admin privileges.

Jaeger and service mesh

Installing Jaeger with the Service Mesh on OpenShift Container Platform differs from community Jaeger installations in multiple ways. These modifications are sometimes necessary to resolve issues, provide additional features, or to handle differences when deploying on OpenShift Container Platform.

  • Jaeger has been enabled by default for Service Mesh.

  • ingress has been enabled by default for Service Mesh.

  • The name for the Zipkin port name has changed to jaeger-collector-zipkin (from http)

  • Jaeger uses Elasticsearch for storage by default.

  • The community version of Istio provides a generic "tracing" route. Red Hat OpenShift Service Mesh uses a "jaeger" route that is installed by the Jaeger operator and is already protected by OAuth.

  • Red Hat OpenShift Service Mesh uses a sidecar for the Envoy proxy, and Jaeger also uses a sidecar, for the Jaeger agent. These two sidecars are configured separately and should not be confused with each other. The proxy sidecar creates spans related to the pod’s ingress and egress traffic. The agent sidecar receives the spans emitted by the application and sends them to the Jaeger Collector.