kubelet-log-config.yaml

# Copyright 2024 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# Deploy this DaemonSet to configure kubelet log rotation on nodes with the
# "kubelet-log-config=true" label.
#
# Change the values of CONTAINER_LOG_MAX_SIZE and CONTAINER_LOG_MAX_FILES to
# suit your needs.
#
# WARNING: Changing the kubelet log rotation configuration requires a kubelet
# restart. Therefore, in order to avoid disrupting your workloads, it is
# recommended to create a new node pool with the "kubelet-log-config=true" label
# in your cluster, deploy the DaemonSet to configure kubelet log rotation in
# that node pool, and then migrate your workloads to the new node pool.

apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: kubelet-log-config
  namespace: kube-system
spec:
  selector:
    matchLabels:
      name: kubelet-log-config
  updateStrategy:
    type: RollingUpdate
  template:
    metadata:
      labels:
        name: kubelet-log-config
    spec:
      tolerations:
      - operator: Exists
      volumes:
      - name: host
        hostPath:
          path: /
      hostPID: true
      initContainers:
      - name: kubelet-log-config
        image: debian
        env:
        # The maximum size of the container log file before it is rotated.
        # Update the value as desired.
        - name: CONTAINER_LOG_MAX_SIZE
          value: "10Mi"
        # The maximum number of container log files that for a container.
        # Update the value as desired.
        - name: CONTAINER_LOG_MAX_FILES
          value: "5"
        command:
        - /bin/bash
        - -c
        - |
          set -xeuo pipefail

          # Configure the kubelet log rotation behavior.
          # $1: Field name in kubelet configuration.
          # $2: Value for the kubelet config field.
          function set-kubelet-log-config() {
            [[ "$#" -eq 2 ]] || return
            local field; field="$1"; shift
            local value; value="$1"; shift

            local config; config="/host/home/kubernetes/kubelet-config.yaml"

            echo "Remove existing configuration for ${field} if there is any."
            sed -i "/${field}/d" "${config}"

            echo "Set ${field} to ${value}."
            echo "${field}: ${value}" >> "${config}"
          }

          set-kubelet-log-config containerLogMaxSize "${CONTAINER_LOG_MAX_SIZE}"
          set-kubelet-log-config containerLogMaxFiles "${CONTAINER_LOG_MAX_FILES}"

          echo "Restarting kubelet..."
          chroot /host nsenter -a -t1 -- systemctl restart kubelet.service

          echo "Success!"
        volumeMounts:
        - name: host
          mountPath: /host
        resources:
          requests:
            memory: 5Mi
            cpu: 5m
        securityContext:
          privileged: true
      containers:
      - image: gcr.io/google-containers/pause:3.2
        name: pause
      # Ensures that the pods will only run on the nodes having the correct
      # label.
      nodeSelector:
        "kubelet-log-config": "true"