⚠️ Please note: In preparation of Flux v2 GA this repository with Flux v1 examples has been archived. The Flux v2 equivalent of what is shown here can be found at flux2-multi-tenancy.Thanks a lot for your interest.
This repository serves as a starting point for a multi-tenant cluster managed with Git, Flux and Kustomize.
I'm assuming that a multi-tenant cluster is shared by multiple teams. The cluster wide operations are performed by the cluster administrators while the namespace scoped operations are performed by various teams each with its own Git repository. That means a team member, that's not a cluster admin, can't create namespaces, custom resources definitions or change something in another team namespace.
First you'll have to create two git repositories:
- a clone of fluxcd-multi-tenancy repository for the cluster admins, I will refer to it as
org/dev-cluster
- a clone of fluxcd-multi-tenancy-team1 repository for the dev team1, I will refer to it as
org/dev-team1
Team | Namespace | Git Repository | Flux RBAC |
---|---|---|---|
ADMIN | all | org/dev-cluster | Cluster wide e.g. namespaces, CRDs, Flux controllers |
DEV-TEAM1 | team1 | org/dev-team1 | Namespace scoped e.g. deployments, custom resources |
DEV-TEAM2 | team2 | org/dev-team2 | Namespace scoped e.g. ingress, services, network policies |
Cluster admin repository structure:
├── .flux.yaml
├── base
│ ├── flux
│ └── memcached
├── cluster
│ ├── common
│ │ ├── crds.yaml
│ │ └── kustomization.yaml
│ └── team1
│ ├── flux-patch.yaml
│ ├── kubeconfig.yaml
│ ├── kustomization.yaml
│ ├── namespace.yaml
│ ├── psp.yaml
│ └── rbac.yaml
├── install
└── scripts
The base
folder holds the deployment spec used for installing Flux in the flux-system
namespace
and in the teams namespaces. All Flux instances share the same Memcached server deployed at
install time in flux-system
namespace.
With .flux.yaml
we configure Flux to run Kustomize build on the cluster dir and deploy the generated manifests:
version: 1
commandUpdated:
generators:
- command: kustomize build .
Development team1 repository structure:
├── .flux.yaml
├── flux-patch.yaml
├── kustomization.yaml
└── workloads
├── frontend
│ ├── deployment.yaml
│ ├── kustomization.yaml
│ └── service.yaml
└── backend
├── deployment.yaml
├── kustomization.yaml
└── service.yaml
The workloads
folder contains the desired state of the team1
namespace and the flux-patch.yaml
contains the
Flux annotations that define how the container images should be updated.
With .flux.yaml
we configure Flux to run Kustomize build, apply the container update policies and deploy the generated manifests:
version: 1
patchUpdated:
generators:
- command: kustomize build .
patchFile: flux-patch.yaml
In the dev-cluster repo, change the git URL to point to your fork:
vim ./install/flux-patch.yaml
[email protected]:org/dev-cluster
Install the cluster wide Flux with kubectl kustomize:
kubectl apply -k ./install/
Get the public SSH key with:
fluxctl --k8s-fwd-ns=flux-system identity
Add the public key to the github.com:org/dev-cluster
repository deploy keys with write access.
The cluster wide Flux will do the following:
- creates the cluster objects from
cluster/common
directory (CRDs, cluster roles, etc) - creates the
team1
namespace and deploys a Flux instance with restricted access to that namespace
Change the dev team1 git URL:
vim ./cluster/team1/flux-patch.yaml
[email protected]:org/dev-team1
When you commit your changes, the system Flux will configure the team1's Flux to sync with org/dev-team1
repository.
Get the public SSH key for team1 with:
fluxctl --k8s-fwd-ns=team1 identity
Add the public key to the github.com:org/dev-team1
deploy keys with write access. The team1's Flux
will apply the manifests from org/dev-team1
repository only in the team1
namespace, this is enforced with RBAC and role bindings.
If team1 needs to deploy a controller that depends on a CRD or a cluster role, they'll
have to open a PR in the org/dev-cluster
repository and add those cluster wide objects in the cluster/common
directory.
The team1's Flux instance can be customised with different options than the system Flux using the cluster/team1/flux-patch.yaml
.
apiVersion: apps/v1
kind: Deployment
metadata:
name: flux
spec:
template:
spec:
containers:
- name: flux
args:
- --manifest-generation=true
- --memcached-hostname=flux-memcached.flux-system
- --memcached-service=
- --git-poll-interval=5m
- --sync-interval=5m
- --ssh-keygen-dir=/var/fluxd/keygen
- --k8s-allow-namespace=team1
- [email protected]:org/dev-team1
- --git-branch=master
The k8s-allow-namespace
restricts Flux discovery mechanism to a single namespace.
Flagger is a progressive delivery Kubernetes operator that can be used to automate Canary, A/B testing and Blue/Green deployments.
You can deploy Flagger by including its manifests in the cluster/kustomization.yaml
file:
bases:
- ./flagger/
- ./common/
- ./team1/
Commit the changes to git and wait for system Flux to install Flagger and Prometheus:
fluxctl --k8s-fwd-ns=flux-system sync
kubectl -n flagger-system get po
NAME READY STATUS
flagger-64c6945d5b-4zgvh 1/1 Running
flagger-prometheus-6f6b558b7c-22kw5 1/1 Running
A team member can now push canary objects to org/dev-team1
repository and Flagger will automate the deployment process.
Flagger can notify your teams when a canary deployment has been initialised, when a new revision has been detected and if the canary analysis failed or succeeded.
You can enable Slack notifications by editing the cluster/flagger/flagger-patch.yaml
file:
apiVersion: apps/v1
kind: Deployment
metadata:
name: flagger
spec:
template:
spec:
containers:
- name: flagger
args:
- -mesh-provider=kubernetes
- -metrics-server=https://flagger-prometheus:9090
- -slack-user=flagger
- -slack-channel=alerts
- -slack-url=https://hooks.slack.com/services/YOUR/SLACK/WEBHOOK
With pod security policies a cluster admin can define a set of conditions that a pod must run with in order to be accepted into the system.
For example you can forbid a team from creating privileged containers or use the host network.
Edit the team1 pod security policy cluster/team1/psp.yaml
:
apiVersion: policy/v1beta1
kind: PodSecurityPolicy
metadata:
name: default-psp-team1
annotations:
seccomp.security.alpha.kubernetes.io/allowedProfileNames: '*'
spec:
privileged: false
hostIPC: false
hostNetwork: false
hostPID: false
allowPrivilegeEscalation: false
allowedCapabilities:
- '*'
fsGroup:
rule: RunAsAny
runAsUser:
rule: RunAsAny
seLinux:
rule: RunAsAny
supplementalGroups:
rule: RunAsAny
volumes:
- '*'
Set privileged, hostIPC, hostNetwork and hostPID to false and commit the change to git. From this moment on, team1 will not be able to run containers with an elevated security context under the default service account.
If a team member adds a privileged container definition in the org/dev-team1
repository, Kubernetes will deny it:
kubectl -n team1 describe replicasets podinfo-5d7d9fc9d5
Error creating: pods "podinfo-5d7d9fc9d5-" is forbidden: unable to validate against any pod security policy:
[spec.containers[0].securityContext.privileged: Invalid value: true: Privileged containers are not allowed]
Gatekeeper is a validating webhook that enforces CRD-based policies executed by Open Policy Agent.
You can deploy Gatekeeper by including its manifests in the cluster/kustomization.yaml
file:
bases:
- ./gatekeeper/
- ./flagger/
- ./common/
- ./team1/
Inside the gatekeeper dir there is a constraint template that instructs OPA to reject Kubernetes deployments if no container resources are specified.
Enable the constraint for team1 by editing the cluster/gatekeeper/constraints.yaml
file:
apiVersion: constraints.gatekeeper.sh/v1alpha1
kind: ContainerResources
metadata:
name: containerresources
spec:
match:
namespaces:
- team1
kinds:
- apiGroups: ["apps"]
kinds: ["Deployment"]
Commit the changes to git and wait for system Flux to install Gatekeeper and apply the constraints:
fluxctl --k8s-fwd-ns=flux-system sync
watch kubectl -n gatekeeper-system get po
If a team member adds a deployment without CPU or memory resources in the org/dev-team1
repository, Gatekeeper will deny it:
kubectl -n team1 logs deploy/flux
admission webhook "validation.gatekeeper.sh" denied the request:
[denied by containerresources] container <podinfo> has no memory requests
[denied by containerresources] container <sidecar> has no memory limits
If you want to add another team to the cluster, first create a git repository as github.com:org/dev-team2
.
Run the create team script:
./scripts/create-team.sh team2
team2 created at cluster/team2/
team2 added to cluster/kustomization.yaml
Change the git URL in cluster/team2
dir:
vim ./cluster/team2/flux-patch.yaml
[email protected]:org/dev-team2
Push the changes to the master branch of org/dev-cluster
and sync with the cluster:
fluxctl --k8s-fwd-ns=flux-system sync
Get the team2 public SSH key with:
fluxctl --k8s-fwd-ns=team2 identity
Add the public key to the github.com:org/dev-team2
repository deploy keys with write access. The team2's Flux
will apply the manifests from org/dev-team2
repository only in the team2
namespace.
With this setup, Flux will prevent a team member from altering cluster level objects or other team's workloads.
In order to harden the tenant isolation, a cluster admin should consider using:
- resource quotas (limit the compute resources that can be requested by a team)
- network policies (restrict cross namespace traffic)
- pod security policies (prevent running privileged containers or host network and filesystem usage)
- Open Policy Agent admission controller (enforce custom policies on Kubernetes objects)
If you have any questions about Flux and GitOps:
- Invite yourself to the CNCF community slack and ask a question on the #flux channel.
- To be part of the conversation about Flux's development, join the flux-dev mailing list.
- Join the Weave User Group and get invited to online talks, hands-on training and meetups in your area.