add host-based calculation for kube cpu/memory reserved resources

docs/operations/cgroups.md

@@ -69,4 +69,17 @@ After the setup, the cgroups hierarchy is as follows:
 └── ...
 ```
 
+## Automatic Resource Reservation Calculation
+
+While manually specifying resource reservations for kube and system daemons works, Kubespray offers a more convenient approach. You can set the `kube_enable_auto_reserved_resources` flag to `true`. This instructs Kubespray to automatically calculate appropriate resource reservations for `kube_[master]_cpu_reserved` and `kube_[master]_memory_reserved` based on your host size. This eliminates the need for manual configuration, simplifying the process.
+
+When `kube_enable_auto_reserved_resources` is set to `true`, Kubespray calculates resource reservations as follows:
+
+CPU: 1% of the total CPU cores on the host machine + 80 millicores
+Memory: 5% of the total available system memory + 330 Megabytes
+
+This approach ensures that kubelet has sufficient resources to function properly while leaving the majority of resources available for your workloads.
+
+After the setup, the cgroups hierarchy remains the same as before.
+
 You can learn more in the [official kubernetes documentation](https://kubernetes.io/docs/tasks/administer-cluster/reserve-compute-resources/).

inventory/sample/group_vars/k8s_cluster/k8s-cluster.yml

@@ -264,6 +264,10 @@ default_kubelet_config_dir: "{{ kube_config_dir }}/dynamic_kubelet_dir"
 
 # Optionally reserve this space for kube daemons.
 # kube_reserved: false
+# If kube_enable_auto_reserved_resources is true,
+# the cpu and memory values are calculated based on the number of CPUs and memory size of the host.
+# The calculation formulas can be seen in https://github.com/kubernetes-sigs/kubespray/blob/master/docs/cgroups.md
+# kube_enable_auto_reserved_resources: false
 ## Uncomment to override default values
 ## The following two items need to be set when kube_reserved is true
 # kube_reserved_cgroups_for_service_slice: kube.slice

roles/kubernetes/node/defaults/main.yml

@@ -9,7 +9,7 @@ kubelet_bind_address: "{{ ip | default('0.0.0.0') }}"
 kube_resolv_conf: "/etc/resolv.conf"
 
 # Set to empty to avoid cgroup creation
-kubelet_enforce_node_allocatable: "\"\""
+kubelet_enforce_node_allocatable: '""'
 
 # Set runtime and kubelet cgroups when using systemd as cgroup driver (default)
 kube_service_cgroups: "{% if kube_reserved %}{{ kube_reserved_cgroups_for_service_slice }}{% else %}system.slice{% endif %}"
@@ -29,10 +29,10 @@ kube_node_addresses: >-
  {{ hostvars[host]['ip'] | default(fallback_ips[host]) }}{{ ' ' if not loop.last else '' }}
  {%- endfor -%}
 kubelet_secure_addresses: "localhost link-local {{ kube_pods_subnet }} {{ kube_node_addresses }}"
-
 # Reserve this space for kube resources
 # Set to true to reserve resources for kube daemons
 kube_reserved: false
+kube_enable_auto_reserved_resources: false
 kube_reserved_cgroups_for_service_slice: kube.slice
 kube_reserved_cgroups: "/{{ kube_reserved_cgroups_for_service_slice }}"
 kube_memory_reserved: 256Mi
@@ -258,7 +258,6 @@ conntrack_modules:
  - nf_conntrack
  - nf_conntrack_ipv4
 
-
 ## Enable distributed tracing for kubelet
 kubelet_tracing: false
 kubelet_tracing_endpoint: 0.0.0.0:4317

roles/kubernetes/node/tasks/kubelet.yml

@@ -18,6 +18,35 @@
  - kubelet
  - kubeadm
 
+- name: Gather facts about the node
+ setup:
+ filter: ansible_memtotal_mb,ansible_processor_vcpus
+ tags:
+ - kubelet
+ - kubeadm
+
+- name: Check if kube_enable_auto_reserved_resources is set
+ set_fact:
+ kube_master_cpu_reserved: "{{ (ansible_processor_vcpus * 1000 * 0.01) | int + 80 }}m"
+ kube_master_memory_reserved: "{{ (ansible_memtotal_mb * 0.05) | int + 330 }}Mi"
+ tags:
+ - kubelet
+ - kubeadm
+ when:
+ - kube_enable_auto_reserved_resources
+ - is_kube_master
+
+- name: Check if kube_enable_auto_reserved_resources is set
+ set_fact:
+ kube_cpu_reserved: "{{ (ansible_processor_vcpus * 1000 * 0.01) | int + 80 }}m"
+ kube_memory_reserved: "{{ (ansible_memtotal_mb * 0.05) | int + 330 }}Mi"
+ tags:
+ - kubelet
+ - kubeadm
+ when:
+ - kube_enable_auto_reserved_resources
+ - not is_kube_master
+
 - name: Write kubelet config file
  template:
  src: "kubelet-config.{{ kubeletConfig_api_version }}.yaml.j2"