Using helm to dynamically set heap size limit based on pod memory limit

_helpers.tpl

{{- define "convertToMB" -}}
{{- $value := . | trim | lower -}}
{{- $result := 0 -}}

{{- if hasSuffix "ki" $value -}}
{{- $num := trimSuffix "ki" $value | float64 -}}
{{- $result = divf $num 1024 -}}
{{- else if hasSuffix "mi" $value -}}
{{- $num := trimSuffix "mi" $value | float64 -}}
{{- $result = $num -}}
{{- else if hasSuffix "gi" $value -}}
{{- $num := trimSuffix "gi" $value | float64 -}}
{{- $result = mulf $num 1024 -}}
{{- else if hasSuffix "ti" $value -}}
{{- $num := trimSuffix "ti" $value | float64 -}}
{{- $result = mulf $num 1048576 -}}
{{- else if hasSuffix "pi" $value -}}
{{- $num := trimSuffix "pi" $value | float64 -}}
{{- $result = mulf $num 1073741824 -}}
{{- else if hasSuffix "ei" $value -}}
{{- $num := trimSuffix "ei" $value | float64 -}}
{{- $result = mulf $num 1099511627776 -}}
{{- else -}}
{{- $num := $value | float64 -}}
{{- $result = divf $num 1048576 -}}
{{- end -}}

{{- (round $result 0) | int -}}
{{- end -}}

{{- define "calculateJSHeapFromPodMemory" -}}
{{- $value := . -}}
{{- $result := sub (include "convertToMB" $value) 50 -}}
{{- $result -}}
{{- end -}}

Usage.md

We wanted to set the max old space size based on the memory limit so that the heap size inside out kubernetes pods is used better.

env:
  - name: NODE_OPTIONS
    value: '--max-old-space-size={{include "calculateJSHeapFromPodMemory" .memory}} --max-semi-space-size=16'