firewall-controller-manager

README

firewall-controller-manager

Overview

The firewall-controller-manager (FCM) is a collection of controllers which are responsible for managing the lifecycle of firewalls in a Gardener shoot cluster for the metal-stack provider.

The FCM is typically deployed into the shoot namespace of a seed cluster. This is done by the gardener-extension-provider-metal.

The design of the FCM is roughly inspired by Gardener's machine-controller-manager and Kubernetes' built-in resources Deployment, ReplicaSet and Pod.

Architecture

The following table is a summary over the CRDs introduced by the FCM:

Custom Resource Object	Description
FirewallDeployment	A FirewallDeployment contains the spec template of a Firewall resource similar to a Deployment and implements update strategies like rolling update.
FirewallSet	A FirewallSet is similar to ReplicaSet. It is typically owned by a FirewallDeployment and attempts to run the defined replica amount of the Firewall(s)
Firewall	A Firewall is similar to a Pod and has a 1:1 relationship to a firewall in the metal-stack api.
FirewallMonitor	Deployed into the cluster of the user (shoot cluster), which is useful for monitoring the firewall or user-triggered actions on the firewall.

FirewallDeploymentController

The FirewallDeployment controller manages the lifecycle of FirewallSets. It syncs the Firewall template spec and if significant changes were made, it may trigger a FirewallSet roll. When choosing RollingUpdate as a deployment strategy, the deployment controller is waiting for the firewall-controller to connect before throwing away an old FirewallSet. The Recreate strategy first releases firewalls before creating a new one (can be useful for environments which ran out of available machines but you still want to update).

The controller also deploys a service account for the firewall-controller to be able to talk to the seed's kube-apiserver.

FirewallSetController

Creates and deletes Firewall objects according to the spec and the given number of firewall replicas. It also checks the status of the Firewall and report that in the own status.

FirewallController

Creates and deletes the physical firewall machine from the spec at the metal-api.

Rolling a FirewallSet through FirewallMonitor Annotation

A user can initiate rolling the latest firewall set by annotating a monitor in the following way:

kubectl annotate fwmon <firewall-name> firewall.metal-stack.io/roll-set=true

Development

Most of the functionality is developed with the help of the intgration test suite.

To play with the FCM, you can also run this controller inside the mini-lab and without a running Gardener installation:

1. Start up the mini-lab, run eval $(make dev-env) and change back to this project's directory
2. Deploy the FCM into the mini-lab with make deploy
3. Adapt the example firewalldeployment.yaml and apply with kubectl apply -f config/examples/firewalldeployment.yaml
4. Note that the firewall-controller will not be able to connect to the mini-lab due to network restrictions, so the firewall will not get ready.
   • You can make the firewall become ready anyway by setting the annotation kubectl annotate fw <fw-nsme> firewall.metal-stack.io/no-controller-connection=true