Kondense

Kondense is an automated resource sizing tool. It runs as a sidecar in kubernetes pods.

Background

Memory

Kondense uses memory pressure to apply just the right amount of memory on a container to page out the unused memory while not getting out-of-memory killed.How is memory calculated ?

CPU

Kondense resizes CPU based on CPU usage, default to 80%.How is CPU calculated ?

Requirements

On Kubernetes

• The Kubernetes cluster must run on Linux.
• Containerd version >= 1.6.9.
• Kubernetes should have the feature gate InPlacePodVerticalScaling enabled.

On Containers

• Containers should include the linux kernel version >= 4.20. Ensure the file /sys/fs/cgroup/memory.pressure exists in the container to verify it.

You can build your containers from the image alpine to be sure.

Example

Try the example on minikube:

minikube start --kubernetes-version=v1.29.2 --feature-gates=InPlacePodVerticalScaling=true
kubectl apply -f https://raw.githubusercontent.com/unagex/kondense/main/example/nginx.yaml

Let's say we have a pod running nginx that we want to Kondense:

apiVersion: v1
kind: Pod
metadata:
  name: kondense-test
spec:
  serviceAccountName: nginx-user
  containers:
  - name: nginx
    image: nginx:latest
    resources:
      limits:
        cpu: 100m
        memory: 100M

Add Kondense as a sidecar:

apiVersion: v1
kind: Pod
metadata:
  name: kondense-test
spec:
  serviceAccountName: nginx-user
  containers:
  - name: nginx
    image: nginx:latest
    resources:
      limits:
        cpu: 0.1
        memory: 100M
  - name: kondense
    image: kondense/kondense:1.1.0
    resources:
      limits:
        cpu: 80m
        memory: 50M

After adding the kondense container, the nginx container resources are updated without any container restart.

Notes:

1. The pod should have a QoS of Guaranteed. In other words, we need to add resources limits for each containers.
2. The service account nginx-user should have the following rules:

rules:
  - apiGroups: [""]
    resources: ["pods"]
    verbs: ["get", "list", "watch", "patch"]
  - apiGroups: [""]
    resources: ["pods/exec"]
    verbs: ["create"]

Configuration

Kondense is configurable via environment variables in the kondense container.

Example

    ...
    - name: kondense
      image: kondense/kondense:1.1.0
      resources:
        limits:
          cpu: 80m
          memory: 50M
      env:
      - name: <CONTAINER NAME>_MEMORY_MIN
        value: "100m"

If we have a container named nginx in our pod, the variable name should be NGINX_MEMORY_MIN.

Environment variables

Global

Memory

CPU

More

• Kondense memory resize is based on Meta Transparent Memory Offloading (TMO)
• Kondense is active on himself by default