Resource in endless modification loop

[mf-lit]

What happened?

I'm observing the following issue when managing an RDSInstance with crossplane.
The resource manifest for the RDSInstance is as follows:

apiVersion: database.aws.crossplane.io/v1beta1
kind: RDSInstance
metadata:
  name: demo-db
spec:
  providerConfigRef:
    name: crossplane-provider-aws  
  forProvider:
    engine: postgres
    engineVersion: "12.5"
    allocatedStorage: 10
    masterUsername: root
    multiAZ: false
    dbInstanceClass: db.t2.small
    region: eu-west-1
    deletionProtection: false
    publiclyAccessible: false
    storageEncrypted: false
    enablePerformanceInsights: false
    skipFinalSnapshotBeforeDeletion: true
    vpcSecurityGroupIds:
      - sg-<redacted>
    dbParameterGroupName: demo-postgres12
    dbSubnetGroupNameRef:
      name: demo-db
  deletionPolicy: Delete
  writeConnectionSecretToRef:
    namespace: crossplane-poc
    name: demo-db

Both the instance and the subnetgroup are created succesfully, but the instance constantly goes in and out of a "modifying" state.

The following event appears on the instance resource:

Normal  UpdatedExternalResource  4m41s (x78 over 40m)  managed/rdsinstance.database.aws.crossplane.io  Successfully requested update of external resource

A bit of digging, and it seems that the ParameterGroup is being "updated" on the instance every few minutes, and so the instance itself keeps flipping-in-and-out-of a Modifying state.

I don't understand why this is occurring and I'm so far unable to troubleshoot further, there's nothing logged by the provider to suggest why it's making this change. I appreciate that I should perhaps be opening this issue against the provider and not crossplane, but some general guidance about how to troubleshoot this would be appreciated, thanks.

What environment did it happen in?

Crossplane version: 1.0
Kubernetes version: (EKS) 1.18, kubectl 1.18

[muvaf]

@mf-lit Thanks for opening the issue! I'll try to reproduce and get back to you.

[muvaf]

some general guidance about how to troubleshoot this would be appreciated, thanks.

https://crossplane.io/docs/v1.1/reference/troubleshoot.html usually helps but in this case, I had to debug the code to see why patch here included the db parameter group name even though it's not changed.

[mf-lit]

Thanks for looking into this @muvaf and for the speedy PR 👏