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Flux vertical scaling
When Flux is managing hundreds of applications that are deployed multiple times per day, cluster admins can fine tune the Flux controller at bootstrap time to run at scale by:
- Increasing the number of workers and resource limits
- Enabling in-memory kustomize builds
- Enabling Helm repository caching to reduce memory usage
- Enabling persistent storage for internal artifacts
- Running the Flux controllers on dedicated nodes
Horizontal scaling
When vertical scaling is not an option, you can use sharding to horizontally scale the Flux controllers. For more details please see the sharding guide.Increase the number of workers and limits
If Flux is managing hundreds of applications, it is advised to increase the number of reconciliations that can be performed in parallel and to bump the resources limits:
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
- gotk-components.yaml
- gotk-sync.yaml
patches:
- patch: |
- op: add
path: /spec/template/spec/containers/0/args/-
value: --concurrent=10
- op: add
path: /spec/template/spec/containers/0/args/-
value: --requeue-dependency=5s
target:
kind: Deployment
name: "(kustomize-controller|helm-controller|source-controller)"
- patch: |
apiVersion: apps/v1
kind: Deployment
metadata:
name: all
spec:
template:
spec:
containers:
- name: manager
resources:
limits:
cpu: 2000m
memory: 2Gi
target:
kind: Deployment
name: "(kustomize-controller|helm-controller|source-controller)"
I/O Device Contention
Note that further increasing the number of concurrent reconciliations for kustomize-controller, without using a RAM-backed filesystem, may not have the desired effect due to IO contention on the Kubernetes node disk.Enable in-memory kustomize builds
When increasing the number of concurrent reconciliations, it is advised
to use tmpfs for the /tmp filesystem to speed up the Flux kustomize build operations:
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
- gotk-components.yaml
- gotk-sync.yaml
patches:
- patch: |
- op: add
path: /spec/template/spec/containers/0/args/-
value: --concurrent=20
- op: replace
path: /spec/template/spec/volumes/0
value:
name: temp
emptyDir:
medium: Memory
target:
kind: Deployment
name: kustomize-controller
Memory usage
Note that tmpfs will count against the controller’s pod memory usage, so it is advised to make use of theGitRepository
ignore feature
to exclude non-YAML files when Flux syncs app repos.Enable Helm repositories caching
If Flux connects to Helm repositories hosting hundreds of Helm charts, it is advised to enable caching to reduce the memory footprint of source-controller:
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
- gotk-components.yaml
- gotk-sync.yaml
patches:
- patch: |
- op: add
path: /spec/template/spec/containers/0/args/-
value: --helm-cache-max-size=10
- op: add
path: /spec/template/spec/containers/0/args/-
value: --helm-cache-ttl=60m
- op: add
path: /spec/template/spec/containers/0/args/-
value: --helm-cache-purge-interval=5m
target:
kind: Deployment
name: source-controller
When helm-cache-max-size is reached, an error is logged and the index is instead
read from file. Cache hits are exposed via the gotk_cache_events_total Prometheus
metrics. Use this data to fine-tune the configuration flags.
Persistent storage for Flux internal artifacts
Flux maintains a local cache of artifacts acquired from external sources.
By default, the cache is stored in an EmptyDir volume, which means that after a restart,
Flux has to restore the local cache by fetching the content of all Git
repositories, Buckets, Helm charts and OCI artifacts. To avoid losing the cached artifacts,
you can configure source-controller with a persistent volume.
Create a Kubernetes PVC definition named gotk-pvc.yaml and place it in your flux-system directory:
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: gotk-pvc
namespace: flux-system
spec:
accessModes:
- ReadWriteOnce
storageClassName: standard
resources:
requests:
storage: 10Gi
Add the PVC file to the kustomization.yaml resources and patch the source-controller volumes:
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
- gotk-components.yaml
- gotk-sync.yaml
- gotk-pvc.yaml
patches:
- patch: |
- op: add
path: '/spec/template/spec/volumes/-'
value:
name: persistent-data
persistentVolumeClaim:
claimName: gotk-pvc
- op: replace
path: '/spec/template/spec/containers/0/volumeMounts/0'
value:
name: persistent-data
mountPath: /data
target:
kind: Deployment
name: source-controller
Node affinity and tolerations
Pin the Flux controller pods to specific nodes and allow the cluster autoscaler to evict them:
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
- gotk-components.yaml
- gotk-sync.yaml
patches:
- patch: |
apiVersion: apps/v1
kind: Deployment
metadata:
name: all
spec:
template:
metadata:
annotations:
cluster-autoscaler.kubernetes.io/safe-to-evict: "true"
spec:
affinity:
nodeAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
nodeSelectorTerms:
- matchExpressions:
- key: role
operator: In
values:
- flux
tolerations:
- effect: NoSchedule
key: role
operator: Equal
value: flux
target:
kind: Deployment
labelSelector: app.kubernetes.io/part-of=flux
The above configuration pins Flux to nodes tainted and labeled with:
kubectl taint nodes <my-node> role=flux:NoSchedule
kubectl label nodes <my-node> role=flux