# Deployments

The deployment modes that Kuma provides are quite unique in the Service Mesh landscape and have been developed thanks to the guidance of our enterprise users, especially when it comes to the distributed one.

There are two deployment models that can be adopted with Kuma in order to address any Service Mesh use-case, from the simple one running in one cluster to the more complex one where multiple Kubernetes or VM clusters are involved, or even hybrid universal ones where Kuma runs simultaneously on Kubernetes and VMs.

The two deployments modes are:

  • Flat: Kuma's default deployment model with one control plane (that can be scaled horizontally) and many data planes connecting directly to it.
  • Distributed: Kuma's advanced deployment model to support multiple Kubernetes or VM-based clusters, or hybrid Service Meshes running on both Kubernetes and VMs combined.

Automatic Connectivity: Running a Service Mesh should be easy and connectivity should be abstracted away, so that when a service wants to consume another service all it needs is the name of the destination service. Kuma achieves this out of the box in both deployment modes with a built-in service discovery and - in the case of the distributed mode - with an Ingress resource and Remote CPs.

# Flat Mode

This is the simplest deployment mode for Kuma, and the default one.

  • Control plane: There is one deployment of the control plane that can be scaled horizontally.
  • Data planes: The data planes connect to the control plane regardless of where they are being deployed.
  • Service Connectivity: Every data plane proxy must be able to connect to every other data plane proxy regardless of where they are being deployed.

This mode implies that we can deploy Kuma and its data plane proxies in a flat networking topology mode so that the service connectivity from every data plane proxy can be established directly to every other data plane proxy.

Although flat mode can support complex multi-cluster or hybrid deployments (Kubernetes + VMs) as long as the networking requirements are satisfied, typically in most use cases our connectivity cannot be flattened out across multiple clusters. Therefore flat mode is usually a great choice within the context of one cluster (ie: within one Kubernetes cluster or one AWS VPC).

For those situations where the flat deployment mode doesn't satisfy our architecture, Kuma provides a distributed mode which is more powerful and provides a greater degree of flexibility in more complex environments.

# Usage

In order to deploy Kuma in a flat deployment, the kuma-cp control plane must be started in standalone mode:

    Once Kuma is up and running, data plane proxies can now connect directly to it.

    When the mode is not specified, Kuma will always start in standalone mode by default.

    # Distributed Mode

    This is a more advanced deployment mode for Kuma that allow us to support service meshes that are running on many clusters, including hybrid deployments on both Kubernetes and VMs.

    • Control plane: There is one global control plane, and many remote control planes. A global control plane only accepts connections from remote control planes.
    • Data planes: The data planes connect to the closest remote control plane in the same zone. Additionally, we need to start an ingress data plane on every zone.
    • Service Connectivity: Automatically resolved via the built-in DNS resolver that ships with Kuma. When a service wants to consume another service, it will resolve the DNS address of the desired service with Kuma, and Kuma will respond with a Virtual IP address, that corresponds to that service in the Kuma service domain.

    We can support multiple isolated service meshes thanks to Kuma's multi-tenancy support, and workloads from both Kubernetes or any other supported Universal environment can participate in the Service Mesh across different regions, clouds and datacenters while not compromising the ease of use and still allowing for end-to-end service connectivity.

    When running in distributed mode, we introduce the notion of a global and remote control planes for Kuma:

    • Global: this control plane will be used to configure the global Service Mesh policies that we want to apply to our data plane proxies. Data plane proxies cannot connect direclty to a global control plane, but can connect to remote control planes that are being deployed on each underlying zone that we want to include as part of the Service Mesh (can be a Kubernetes cluster, or a VM based cluster). Only one deployment of the global control plane is required, and it can be scaled horizontally.
    • Remote: we are going to have as many remote control planes as the number of underlying Kubernetes or VM zones that we want to include in a Kuma mesh. Remote control planes will accept connections from data planes that are being started in the same underlying zone, and they will themselves connect to the global control plane in order to fetch the service mesh policies that have been configured. Remote control plane policy APIs are read-only and cannot accept Service Mesh policies to be directly configured on them. They can be scaled horizontally within their zone.

    In this deployment, a Kuma cluster is made of one global control plane and as many remote control planes as the number of zones that we want to support:

    • Zone: A zone identifies a Kubernetes cluster, a VPC, or any other cluster that we want to include in a Kuma service mesh.

    In a distributed deployment mode, services will be running on multiple platforms, clouds or Kubernetes clusters (which are identifies as zones in Kuma). While all of them will be part of a Kuma mesh by connecting their data plane proxies to the local remote control plane in the same zone, implementing service to service connectivity would be tricky since a source service may not know where a destination service is being hosted at (for instance, in another zone).

    To implement easy service connectivity, Kuma ships with:

    • DNS Resolver: Kuma provides an out of the box DNS server on every remote control plane that will be used to resolve service addresses when establishing any service-to-service communication. It scales horizontally as we scale the remote control plane.
    • Ingress Data Plane: Kuma provides an out of the box ingress data plane mode that will be used to enable traffic to enter a zone from another zone. It can be scaled horizontally. Each zone must have an ingress data plane deployed.

    An ingress data plane is specific to internal communication within a mesh and it is not to be considered an API gateway. API gateways are supported via Kuma's gateway mode which can be deployed in addition to ingress data planes.

    The global control plane and the remote control planes communicate with each other via xDS in order to synchronize the resources that are being created to configure Kuma, like policies.

    For Kubernetes: The global control plane on Kubernetes must reside on its own Kubernetes cluster, in order to keep the CRDs separate from the ones that the remote control planes will create during the synchronization process.

    # Usage

    In order to deploy Kuma in a distributed deployment, we must start a global and as many remote control planes as the number of zones that we want to support.

    It is recommended that we start the remote control planes in each zone we want to connect.

      The next step is to start the global control plane and configure the remote control planes connectivity.

        Where <global_cp_ip> is the IP address of the Load Balancer that expose the global control plane synchronisation service. <zone-1_ip> is the IP address of the Load Balancer of the remote control plane. The latter can be used for both the sync service remote: and the ingress:.

        To utilize the distributed Kuma deployment follow the steps below

          The Kuma DNS service format (e.g. echo-server_kuma-test_svc_1010.mesh) is a composition of Kubernetes Service Name (echo-server), Namespace (kuma-test), a fixed string (svc), the service port (1010). The service is resolvable in the DNS zone .mesh where the Kuma DNS service is hooked.

          Last Updated: 9/25/2020, 5:22:32 AM