ACK RDS controller false diff when creating DBParameterGroup with log_checkpoints: '1'

[eTimS]

Hello,

Describe the bug
Creating a DBParameterGroup with log_checkpoints: '1' in the parameterOverrides leads to permanent diff.

Steps to reproduce
Use rds-chart:1.6.0 (bug also observed with rds-chart:1.4.1)
with the following values (all settings have been copied in case they are relevant):

aws:
  region: eu-west-3
deployment:
  replicas: 3
leaderElection:
  enabled: true
metrics:
  service:
    create: true
reconcile:
  defaultMaxConcurrentSyncs: 10
  defaultResyncPeriod: 60 # Debug value to show the diff message in the controller logs every minute instead of 10 hours
serviceAccount:
  annotations:
    eks.amazonaws.com/role-arn: <insert your IRSA ARN here>

Apply the two following manifests:

• dpg.yaml :

  apiVersion: rds.services.k8s.aws/v1alpha1
  kind: DBParameterGroup
  metadata:
    name: dpg-postgres
    namespace: default
  spec:
    description: Parameter group with no diff issue
    family: postgres17
    name: dpg-postgres
    parameterOverrides:
      hot_standby_feedback: '1'
      # log_checkpoints: '1'
      log_connections: '1'
      log_lock_waits: '1'
      log_min_duration_statement: '10000'
      log_rotation_age: '1440'
      shared_preload_libraries: pg_stat_statements

• dpg-permanent-diff.yaml :

  apiVersion: rds.services.k8s.aws/v1alpha1
  kind: DBParameterGroup
  metadata:
    name: dpg-permanent-diff-postgres
    namespace: default
  spec:
    description: Parameter group with permanent diff issue
    family: postgres17
    name: dpg-permanent-diff-postgres
    parameterOverrides:
      hot_standby_feedback: '1'
      log_checkpoints: '1'
      log_connections: '1'
      log_lock_waits: '1'
      log_min_duration_statement: '10000'
      log_rotation_age: '1440'
      shared_preload_libraries: pg_stat_statements

The only difference is adding the log_checkpoints: '1' which causes permanent drift detection.
After one minute, notice in the controller logs that a diff is noticed for the DBParameterGroup named "dpg-permanent-diff-postgres" but not for "dpg-postgres" :

{"level":"info","ts":"2025-09-01T14:50:05.906Z","logger":"ackrt","msg":"desired resource state has changed","kind":"DBParameterGroup","namespace":"default","name":"dpg-permanent-diff-postgres","account":"[redacted]","role":"","region":"eu-west-3","is_adopted":false,"generation":1,"diff":[{"Path":{"Parts":["Spec","ParameterOverrides"]},"A":{"hot_standby_feedback":"1","log_checkpoints":"1","log_connections":"1","log_lock_waits":"1","log_min_duration_statement":"10000","log_rotation_age":"1440","shared_preload_libraries":"pg_stat_statements"},"B":{"hot_standby_feedback":"1","log_connections":"1","log_lock_waits":"1","log_min_duration_statement":"10000","log_rotation_age":"1440","shared_preload_libraries":"pg_stat_statements"}}]}

The logs seems to indicate that the controller "doesn't see" "log_checkpoints":"1" in the parameter group and wants to modify the parameter group to reconcile. Double checking with the AWS RDS Console proved the "log_checkpoints":"1" is actually correctly set on the parameter group.

Expected outcome
We expect no diff to be detected since the "dpg-permanent-diff-postgres" is appropriately configured and synced.

Environment

• Kubernetes version
  1.31
• Using EKS (yes/no), if so version?
  eks.34
• AWS service targeted (S3, RDS, etc.)
  RDS

[github-actions]

Hello @eTimS 👋 Thank you for opening an issue in ACK! A maintainer will triage this issue soon.

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You can find more information about ACK on our website.

[mmclane]

I think I am also seeing (or at least something like this) this today.

[mmclane]

changing log_checkpoints in the parameter group to 0 doesn't make a difference. I still see that the database is continuing to reapply the parameter group. Having read the description of this ticket I am actually seeing something different. I am not creating a parameter group with ACK, only the RDS DBInstances. But what I see is that ACK is trying to update the parameter group every 2 minutes so its basically in a constant state of being modified.