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Contiv KSR (Kubernetes State Reflector)

Introduction

contiv-ksr subscribes to K8s, watches for state changes of specific resources (currently: namespaces, pods, policies) and propagates received updates into the ETCD datastore as protobuf-formatted key-value data. contiv-agent watches and reads these K8s state data from ETCD primarily in order to configure network policies between pods.

Protocol

State data of k8s resources are stored into the data store in a protobuf format. Each resource type has its own data model and a key prefix under which the formatted data are stored:

  • Namespace:
    • data model
    • key: /vnf-agent/contiv-ksr/k8s/namespace/{namespace-name}
  • Pod:
    • data model
    • key: /vnf-agent/contiv-ksr/k8s/namespace/{namespace-name}/pod/{pod-name}
  • Network Policy:
    • data model
    • key: /vnf-agent/contiv-ksr/k8s/namespace/{namespace-name}/policy/{policy-name}

Configuration

The location of the ETCD configuration file is defined either with the --etcd-config argument or through the ETCD_CONFIG environment variable. The attached example configuration file etcd.conf (used by default if PWD is this directory) assumes that ETCD listens on the localhost, port 22379 for client communication.

Additionally, contiv-ksr reads kubeconfig to get the access credentials and the address of the K8s cluster that it should connect to. The location of kubeconfig is specified either with the --kube-config argument or through the KUBE_CONFIG environment variable. If not specified, contiv-ksr will grab the default admin credentials from: /etc/kubernetes/admin.conf.

Additionally, contiv-ksr exposes REST API for a remote management. Currently, only loggers can be configured remotely:

  • list all registered loggers: 
    curl -X GET http://<host>:<port>/log/list
  • set log level for a registered logger: 
    curl -X PUT http://<host>:<port>/log/<logger-name>/<log-level>

By default, the REST API is attached to the port 9191, but the address can be changed in the configuration file passed with the --http-config CLI option (or through HTTP_CONFIG env. variable), see attached http.conf.

The interesting loggers for contiv-ksr are:

  • ksr-namespace: log messages associated with processing of changes in k8s namespaces
  • ksr-policy: log messages associated with processing of changes in k8s policies
  • ksr-pod: log messages associated with processing of changes in k8s pods

Requirements

To start contiv-ksr you have to have Kubernetes 1.8+ and (a separate) ETCD running first.

kubeadm can be used to easily and quickly install a Kubernetes cluster, see: https://kubernetes.io/docs/setup/independent/create-cluster-kubeadm/

ETCD deployed by kubeadm does not accept remote connections, therefore you need to start a new instance and attach it to a different port (choose port number 22379 to match with the attached example configuration).

If you don't have ETCD installed locally, you can use the following docker image:

sudo docker run -p 22379:2379 --name etcd --rm \
    quay.io/coreos/etcd:v3.0.16 /usr/local/bin/etcd \
    -advertise-client-urls http://0.0.0.0:2379 \
    -listen-client-urls http://0.0.0.0:2379

Usage

Start contiv-ksr with:

./contiv-ksr [--etcd-config <config-filepath>] \
             [--http-config <config-filepath>] \
             [--kube-config <config-filepath>]

Run contiv-ksr with enough privileges to read the selected configuration files. For example, kubeconfig admin.conf requires superuser privileges.