kubernetes config map data value externalisation - kubernetes

Question

I'm installing fluent-bit in our k8s cluster. I have the helm chart for it on our repo, and argo is doing the deployment.
Among the resources in the helm chart is a config-map with data value as below:
apiVersion: v1
kind: ConfigMap
metadata:
name: fluent-bit
labels:
app: fluent-bit
data:
...
output-s3.conf: |
[OUTPUT]
Name s3
Match *
bucket bucket/prefix/random123/test
region ap-southeast-2
...
My question is how can I externalize the value for the bucket so it's not hardcoded (please note that the bucket value has random numbers)? As the s3 bucket is being created by a separate app that gets ran on the same master node, the randomly generated s3 bucket name is available as environment variable, e.g. doing "echo $s3bucketName" on the node would give the actual value).
I have tried doing below on the config map but it didn't work and is just getting set as it is when inspected on pod:
bucket $(echo $s3bucketName)
Using helm, I know it can be achieved something like below and then can populate using scripting something like helm --set to set the value from environment variable. But the deployment is happening auto through argocd so it's not like there is a place to do helm --set command or please let me know if otherwise.
bucket {{.Values.s3.bucket}}
TIA

Answer 1

Instead of using helm install you can use helm template ... --set ... > out.yaml to locally render your chart in a yaml file. This file can then be processed by Argo.
Docs

Answer 2

With FluentBit you should be able to use environment variables such as:
output-s3.conf: |
[OUTPUT]
Name s3
Match *
bucket ${S3_BUCKET_NAME}
region ap-southeast-2
You can then set the environment variable on your Helm values. Depending on the chart you are using and how values are passed you may have to perform a different setup, but for example using the official FluentBit charts with a values-prod.yml like:
env:
- name: S3_BUCKET_NAME
value: "bucket/prefix/random123/test"
Using ArgoCD, you probably have a Git repository where Helm values files are defined (like values-prod.yml) and/or an ArgoCD application defining values direct. For example, if you have an ArgoCD application defined such as:
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
# [...]
spec:
source:
# ...
helm:
# Helm values files for overriding values in the helm chart
valueFiles:
# You can update this file
- values-prod.yaml
# Helm values
values: |
# Or update values here
env:
- name: S3_BUCKET_NAME
value: "bucket/prefix/random123/test"
# ...
You should be able to update either values-prod.yml on the repository used by ArgoCD or update directly values: with you environment variable