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Conduit

The Conduit defines a physical path of chained network services the traffic will pass before it can be consumed by the target application. The Traffic is assigned to the Conduit by Stream. Currently, the only supported network service function is stateless load balancing.

The picture below describes 2 conduits. the left one is a stateless load-balancer and the right one is a SCTP network service. The left user pod has subscribed to one or more stream the stateless load-balancer is handling, so it is connected to it via a new network interface. The right user pod has subscribed to streams the stateless load-balancer and the SCTP network services are handling, so it is connected to them via two new network interfaces, one connected to the stateless load-balancer network service, and the other one connected to the SCTP network service.

This resource must be created with label metadata.labels.trench to specify its owner reference trench.

Overview-Conduit

API

Types

TODO

Stateless load balancer

The Stateless load balancer type (.spec.type: stateless-lb) provides stateless load-balancing network function via the Maglev algorithm.

Here is an example of a stateless-lb conduit object:

apiVersion: meridio.nordix.org/v1
kind: Conduit
metadata:
  name: conduit-a-1
  labels:
    trench: trench-a
spec:
  type: stateless-lb

Port-NAT

As defined in the use cases, NATting might require it in order to expose their service with certain ports. By default, privileged ports under 1024 require root or CAP_NET_BIND_SERVICE in order to bind to them. Therefore, applications must NAT service port to an unprivileged port open on their host.

Here is an example of destination port NATting in a conduit object:

apiVersion: meridio.nordix.org/v1
kind: Conduit
metadata:
  name: conduit-a-1
  labels:
    trench: trench-a
spec:
  type: stateless-lb
  destination-port-nats:
  - port: 80
    target-port: 4000
    vips:
    - vip-a-1-v4
    - vip-a-1-v6
    protocol: "tcp"

All TCP traffic with vip-a-1-v4 or vip-a-1-v6 as desination IP and 80 as destination port will get the destination port translated to 4000.

Deployment

After deploying the example from the previous section, the following resources have been created in Kubernetes:

$ kubectl get conduits
NAME          TYPE           TRENCH
conduit-a-1   stateless-lb   trench-a

A daemonset:

  • proxy-<conduit-name>
$ kubectl get daemonsets
NAME                DESIRED   CURRENT   READY   UP-TO-DATE   AVAILABLE   NODE SELECTOR   AGE
proxy-conduit-a-1   2         2         2       2            2           <none>          67s

$ kubectl get pods
NAME                      READY   STATUS    RESTARTS   AGE
proxy-conduit-a-1-tbjgg   1/1     Running   0          67s
proxy-conduit-a-1-w4qbk   1/1     Running   0          67s

The meridio-configuration-<trench-name> configmap has also been configured.

The picture below represents a Kubernetes cluster with Conduit applied and highlighted in red: Installation-Conduit

Limitations

  • .metadata.name has a limit of 57 (63 - RESOURCE_NAME_PREFIX - 6) characters.
    • 63: The maximum length for .metadata.name in Kubernetes.
    • RESOURCE_NAME_PREFIX: An environemnt variable in the operator adding a prefix to the resources being deployed.
    • 6: Due to the pods names in the proxy deployment.
  • .metadata.labels.trench property is mandatory and immutable.
  • .spec.type property is mandatory and immutable.

Configuration

TODO: Update

Name Type Description Required Default
name string Name of the Conduit yes
trench string Name of the Trench the Conduit belongs to yes
destination-port-nats []PortNat List of destination ports to NAT. no