In a Helm template, is it possible to override specific properties if there are same key with different values

Question

1st_values.yaml

  runtimeProperties:|
    druid.broker.http.numConnections=300
    druid.server.http.numThreads=180

2nd_values.yaml

  runtimePropertiesExtra:|
    druid.broker.http.numConnections=500
    druid.sql.enable=true

So if I use the command helm template -f 1st_values.yaml -f 2nd_values.yaml .

I'm getting the output like this

  runtimeProperties:|
    druid.broker.http.numConnections=300
    druid.server.http.numThreads=180
    druid.broker.http.numConnections=500
    druid.sql.enable=true

But ideally it should be like this

    druid.server.http.numThreads=180
    druid.broker.http.numConnections=500
    druid.sql.enable=true

This is my template I'm using, This sucessfully appends the value

      runtime.properties: |
        {{- with .Values.broker.runtimeProperties -}}
          {{ . | nindent 8 }}
        {{- end }}
        {{- with .Values.broker.runtimePropertiesExtra -}}
          {{ . | indent 8 | trim }}
        {{- end }}

Answer 1

As far as Helm is concerned, you've given it two values runtimeProperties and runtimePropertiesExtra that both have string values. Helm has no notion of "properties file" as a type, and there are no Helm extension functions that could readily parse or merge these strings.

One possibility is to express the settings as YAML structure in the Helm values, and then convert it to a properties file in template code. For example, if the values say

runtimeProperties:
  druid.broker.http.numConnections: 300
  druid.server.http.numThreads: 180
runtimePropertiesExtra:
  druid.broker.http.numConnections: 500
  druid.sql.enable: true

Then you can write a helper function to convert this to properties syntax

{{- define "dict-to-properties" -}}
{{- range $k, $v := . -}}
{{ $k }}={{ $v }}
{{ end -}}
{{- end -}}

Then when you create the ConfigMap, you can use the merge function to combine the two maps:

{{- $propdict := dict -}}
{{- mergeOverwrite $propdict .Values.runtimeProperties .Values.runtimePropertiesExtra -}}
data:
  runtime.properties: |
{{ include "dict-to-properties" $propdict | indent 4 }}

On the off chance that these properties are being used in a Spring Boot application, that framework can directly read YAML files as input, and you can use the Helm toYaml function instead of the dict-to-properties helper shown here. merge(Overwrite) does a deep merge, and so you could use a fully-structured YAML block rather than writing out dot-syntax properties.