Required Permissions

Overview

All of StackState's own components can run without any extra permissions. However, StackState uses Elasticsearch, and there are some additional requirements for the nodes that this runs on.

As the vm.max_map_count Linux system setting is usually lower than required for Elasticsearch to start, an init container is used that runs in privileged mode and as the root user. The init container is enabled by default to allow the vm.max_map_count system setting to be changed.

Disable the privileged Elasticsearch init container

In case you and/or your Kubernetes administrators do not want the privileged Elasticsearch init container to be enabled by default, you can disable this behavior in the file values.yaml used to install StackState:

values.yaml
values.yaml
elasticsearch:
sysctlInitContainer:
enabled: false

If this is disabled, you will need to ensure that the vm.max_map_count setting is changed from its common default value of 65530 to 262144. If this is not done, Elasticsearch will fail to start up and its pods will be in a restart loop.

To inspect the current vm.max_map_count setting, run the following command. Note that it runs a privileged pod:

kubectl run -i --tty sysctl-check-max-map-count --privileged=true --image=busybox --restart=Never --rm=true -- sysctl vm.max_map_count

If the current vm.max_map_count setting is not at least 262144, it will need to be increased in a different way or Elasticsearch will fail to start up and its pods will be in a restart loop. The logs will contain an error message like this:

bootstrap checks failed
max virtual memory areas vm.max_map_count [65530] is too low, increase to at least [262144]

Increase Linux system settings for Elasticsearch

Depending on what your Kubernetes administrators prefer, the vm.max_map_count can be set to a higher default on all nodes by either changing the default node configuration (for example via init scripts) or by having a DaemonSet do this right after node startup. The former is very dependent on your Kuberentes cluster setup, so there are no general solutions there.

Below is an example that can be used as a starting point for a DaemonSet to change the vm.max_map_count setting:

apiVersion: apps/v1
kind: DaemonSet
metadata:
name: set-vm-max-map-count
labels:
k8s-app: set-vm-max-map-count
spec:
selector:
matchLabels:
name: set-vm-max-map-count
template:
metadata:
labels:
name: set-vm-max-map-count
spec:
# Make sure the setting always gets changed as soon as possible:
tolerations:
- effect: NoSchedule
operator: Exists
- effect: NoExecute
key: node.kubernetes.io/not-ready
operator: Exists
# Optional node selector (assumes nodes for Elasticsearch are labeled `elastichsearch:yes`
# nodeSelector:
# elasticsearch: yes
initContainers:
- name: set-vm-max-map-count
image: busybox
securityContext:
runAsUser: 0
privileged: true
command: ["sysctl", "-w", "vm.max_map_count=262144"]
resources:
limits:
cpu: 100m
memory: 100Mi
requests:
cpu: 100m
memory: 100Mi
# A pause container is needed to prevent a restart loop of the pods in the daemonset
# See also this Kuberentes issue https://github.com/kubernetes/kubernetes/issues/36601
containers:
- name: pause
image: google/pause
resources:
limits:
cpu: 50m
memory: 50Mi
requests:
cpu: 50m
memory: 50Mi

To limit the number of nodes that this is applied to, nodes can be labeled. NodeSelectors on both this DaemonSet, as shown in the example, and the Elasticsearch deployment can then be set to run only on nodes with the specific label. For Elasticsearch, the node selector can be specified via the values:

elasticsearch:
nodeSelector:
elasticsearch: yes
sysctlInitContainer:
enabled: false

See also