sysctl: add chart to allow us to configure worker kernel params

As reported in "Understand why system CPU usage is so high"[1], we see
that the kernel spends a lot of time trying to reclaim memory for itself
when a bunch of containers start running on those VMs.

By adjusting the minimum amount of reserved memory for the kernel to a
higher value, we're able to then let it do less work.

With the introduction of the `sysctl` chart, every time a new `worker`
node gets in, the pod in the daemonset will get scheduled to it, thus,
the parameters we want will be set on such selected set of nodes.

[1]: #22

Signed-off-by: Ciro S. Costa <[email protected]>

deployments/without-creds/sysctl/.helmignore

@@ -0,0 +1,22 @@
+# Patterns to ignore when building packages.
+# This supports shell glob matching, relative path matching, and
+# negation (prefixed with !). Only one pattern per line.
+.DS_Store
+# Common VCS dirs
+.git/
+.gitignore
+.bzr/
+.bzrignore
+.hg/
+.hgignore
+.svn/
+# Common backup files
+*.swp
+*.bak
+*.tmp
+*~
+# Various IDEs
+.project
+.idea/
+*.tmproj
+.vscode/

deployments/without-creds/sysctl/Chart.yaml

@@ -0,0 +1,5 @@
+apiVersion: v1
+appVersion: "1.0"
+description: A Helm Chart for configuring kernel parameters
+name: sysctl
+version: 0.1.0

deployments/without-creds/sysctl/templates/_helpers.tpl

@@ -0,0 +1,32 @@
+{{/* vim: set filetype=mustache: */}}
+{{/*
+Expand the name of the chart.
+*/}}
+{{- define "sysctl.name" -}}
+{{- default .Chart.Name .Values.nameOverride | trunc 63 | trimSuffix "-" -}}
+{{- end -}}
+
+{{/*
+Create a default fully qualified app name.
+We truncate at 63 chars because some Kubernetes name fields are limited to this (by the DNS naming spec).
+If release name contains chart name it will be used as a full name.
+*/}}
+{{- define "sysctl.fullname" -}}
+{{- if .Values.fullnameOverride -}}
+{{- .Values.fullnameOverride | trunc 63 | trimSuffix "-" -}}
+{{- else -}}
+{{- $name := default .Chart.Name .Values.nameOverride -}}
+{{- if contains $name .Release.Name -}}
+{{- .Release.Name | trunc 63 | trimSuffix "-" -}}
+{{- else -}}
+{{- printf "%s-%s" .Release.Name $name | trunc 63 | trimSuffix "-" -}}
+{{- end -}}
+{{- end -}}
+{{- end -}}
+
+{{/*
+Create chart name and version as used by the chart label.
+*/}}
+{{- define "sysctl.chart" -}}
+{{- printf "%s-%s" .Chart.Name .Chart.Version | replace "+" "_" | trunc 63 | trimSuffix "-" -}}
+{{- end -}}

deployments/without-creds/sysctl/templates/daemonset.yaml

@@ -0,0 +1,52 @@
+apiVersion: apps/v1
+kind: DaemonSet
+metadata:
+  name: {{ include "sysctl.fullname" . }}
+  labels:
+    app.kubernetes.io/name: {{ include "sysctl.name" . }}
+    helm.sh/chart: {{ include "sysctl.chart" . }}
+    app.kubernetes.io/instance: {{ .Release.Name }}
+    app.kubernetes.io/managed-by: {{ .Release.Service }}
+spec:
+  selector:
+    matchLabels:
+      app.kubernetes.io/name: {{ include "sysctl.name" . }}
+      app.kubernetes.io/instance: {{ .Release.Name }}
+  template:
+    metadata:
+      labels:
+        app.kubernetes.io/name: {{ include "sysctl.name" . }}
+        app.kubernetes.io/instance: {{ .Release.Name }}
+    spec:
+      containers:
+        - name: {{ .Chart.Name }}
+          image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
+          imagePullPolicy: {{ .Values.image.pullPolicy }}
+          securityContext:
+            privileged: true
+          terminationGracePeriodSeconds: '5'
+          command:
+            - /bin/sh
+            - -c
+            - |
+              set -o errexit
+              set -o xtrace
+
+              {{- if empty .Values.sysctl }}
+                {{ fail "at least one sysctl option must be set." }}
+              {{- end }}
+
+              while sysctl -w {{ range .Values.sysctl }}{{ . }}{{- end }}
+              do
+                sleep 120s
+              done
+          resources:
+            {{- toYaml .Values.resources | nindent 12 }}
+      {{- with .Values.nodeSelector }}
+      nodeSelector:
+        {{- toYaml . | nindent 8 }}
+      {{- end }}
+    {{- with .Values.affinity }}
+      affinity:
+        {{- toYaml . | nindent 8 }}
+    {{- end }}

deployments/without-creds/sysctl/values.yaml

@@ -0,0 +1,30 @@
+image:
+  repository: busybox
+  tag: latest
+  pullPolicy: IfNotPresent
+
+nameOverride: ""
+fullnameOverride: ""
+
+resources:
+  limits:
+    cpu: 50m
+    memory: 20Mi
+  requests:
+    cpu: 50m
+    memory: 20Mi
+
+nodeSelector:
+  cloud.google.com/gke-nodepool: workers-1
+
+affinity: {}
+
+# A list of `sysctl` values to configure.
+# For instance:
+#
+#   sysctl: [ "vm.min_free_kbytes=7852" ]
+#
+# Note: at least one value must be configured.
+#
+sysctl:
+  - vm.min_free_kbytes=1000000