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Mesh
This resource describes a very important concept in Kuma, and that is the ability of creating multiple isolated service meshes within the same Kuma cluster which in turn make Kuma a very simple and easy project to operate in environments where more than one mesh is required based on security, segmentation or governance requirements.
Typically we would want to create a Mesh per line of business, per team, per application or per environment or for any other reason. Typically multiple meshes are being created so that a service mesh can be adopted by an organization with a gradual roll-out that doesn’t require all the teams and their applications to coordinate with each other, or as an extra layer of security and segmentation for our services so that - for example - policies applied to one Mesh do not affect another Mesh.
Mesh is the parent resource of every other resource in Kuma, including:
In order to use Kuma at least one Mesh must exist, and there is no limit to the number of Meshes that can be created. When a data plane proxy connects to the control plane (kuma-cp) it specifies to what Mesh resource it belongs: a data plane proxy can only belong to one Mesh at a time.
When starting a new Kuma cluster from scratch a default Mesh is being created automatically.
Besides the ability of being able to create virtual service mesh, a Mesh resource will also be used for:
- Mutual TLS, to secure and encrypt our service traffic and assign an identity to the data plane proxies within the Mesh.
- Traffic Metrics, to setup metrics backend that will be used to collect and visualize metrics of our service mesh and service traffic within the Mesh.
- Traffic Trace, to setup tracing backends that will be used to collect traces of our service traffic within the Mesh.
When Mutual TLS is enabled in builtin mode, each Mesh will provision its own CA root certificate and key unless we explicitly decide to use the same CA by sharing the same certificate and key across multiple meshes. When the CAs of our Meshes are different, data plane proxies from one Mesh will not be able to consume data plane proxies belonging to another Mesh and an intermediate API Gateway must be used in order to enable cross-mesh communication. Kuma supports a gateway mode to make this happen.
Usage
The easiest way to create a Mesh is to specify its name. The name of a Mesh must be unique.
apiVersion: kuma.io/v1alpha1
kind: Mesh
metadata:
name: default
We will apply the configuration with kubectl apply -f [..].
Creating resources in a Mesh
It is possible to determine to what Mesh other resources belong to in the following ways.
Data plane proxies
Every time we start a data plane proxy, we need to specify to what Mesh it belongs, this can be done in the following way:
By using the kuma.io/mesh annotation in a Deployment, like:
apiVersion: apps/v1
kind: Deployment
metadata:
name: example-app
namespace: kuma-example
spec:
...
template:
metadata:
...
annotations:
# indicate to Kuma what is the Mesh that the data plane proxy belongs to
kuma.io/mesh: default
spec:
containers:
...
A Mesh may span multiple Kubernetes namespaces. Any Kuma resource in the cluster which
specifies a particular Mesh will be part of that Mesh.
Policies
When creating new Policies we also must specify to what Mesh they belong. This can be done in the following way:
By using the mesh property, like:
apiVersion: kuma.io/v1alpha1
kind: TrafficRoute
mesh: default # indicate to Kuma what is the Mesh that the resource belongs to
metadata:
name: route-1
spec:
...
Kuma consumes all Policies on the cluster and joins each to an individual Mesh, identified by this property.
Controlling the passthrough mode
In its default setup, Kuma allows any non-mesh traffic to pass Envoy without applying any policy. For instance if a service needs to send a request to http://example.com, all requests won’t be logged even if a traffic logging is enabled in the mesh where the service is deployed.
The passthrough mode is enabled by default on all the dataplane proxies in transparent mode in a Mesh. This behavior can be changed by setting the networking.outbound.passthrough in the Mesh resource. Example:
apiVersion: kuma.io/v1alpha1
kind: Mesh
metadata:
name: default
spec:
networking:
outbound:
passthrough: false
When networking.outbound.passthrough is false, no traffic to any non-mesh resource can leave the Mesh.
Before turning this feature on, double-check Envoy stats that no traffic is flowing through pass_through cluster. Otherwise, you will block the traffic which may cause the instability of the system.