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current_limitations.md

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Current Limitations

General Limitations

  • The a8s control plane components (PostgreSQL-Operator, a8s-Backup-Manager, a8s- Service-Binding-Controller) currently do not support HA setups.

  • Currently almost no component of a8s supports TLS. The only communication that uses TLS is the one between the Kubernetes API server and an a8s validating webhook that performs basic syntactic validation on the PostgreSQL instances API objects. Communication between:

    • DSI replicas
    • applications and DSIs
    • DSIs and a8s control plane components
    • a8s control plane components
    • Kubernetes API servers and a8s control plane components

    doesn't use TLS at the moment, with the exception mentioned above. We plan to add that very soon.

PostgreSQL Instances

  • The PostgreSQL server port is hardcoded to 5432.
  • Only PostgreSQL version 13 and 14 are supported.
  • Horizontal down scaling is not supported, i.e. you can not scale down the number of replicas.
  • Each instance stores its data in a dedicated PersistentVolumeClaim of the default StorageClass; Currently only this PersistentVolumeClaims size can be configured
  • Instance names have to be shorter than 53 characters. That is, their maximum length is 52 characters. Attempts to create an instance with a longer name will fail immediately.
  • Currently a8s doesn't enforce any multi-tenancy/access control regarding the Instances it manages. This means that unless you or the Kubernetes cluster administrator explicitly set up RBAC rules and Network Policies to prevent that, every user of the Kubernetes cluster can interact in any possible way with any PostgreSQL instance (e.g. provision, deprovision, take backups, create a service binding and use it to write/read data to/from the instance, etc...).
  • Given an instance, there's no multi-tenancy: all service bindings to it will share the same database.

Backup and Restore

  • Only AWS S3 buckets are supported as backup storage.

  • Open connections (idle or active) to the PostgreSQL server during a restore can lead to silent failure of the restore. More specifically, the data in the backup used for the restore is appended to the data already in the database, rather than being used as a replacement for it.

  • The backup encryption key is stored in plain text as part of the backup manager configuration.

  • Point-In-Time-Recovery (PITR) is not supported.

  • We currently do not support the creation of a periodic backup schedule.

  • The deletion of Recovery API objects can hang indefinitely in some rare cases. If you encounter this issue, run the command:

    kubectl patch -n <namespace of the recovery> \
  recoveries.backups.anynines.com/<name of the recovery> \
  -p '{"metadata":{"finalizers":[]}}' --type=merge

    to force the deletion.

Service Bindings

  • Custom parameters for configuring the permissions are not supported.
  • All Service Bindings of a single DSI share the a9s_apps_default_db database.
  • Service Bindings can only be used in the namespace they are created in, the reason behind that is that the secrets, where the password and username are stored, are limited to a single namespace (see Kubernetes Secrets)

Logging

  • OpenDashboards has the authentication disabled, this means that the dashboard can be accessed from anyone that can reach its URL.
  • We currently do not support multiple logging destinations or a separation of logs for different users. All logs will be shipped to a single instance OpenSearch and are accessible from the dashboard.

Metrics

  • Here we also do not support multi-tenancy, analogous to Logging this implies that we do not support multiple destinations or metrics for different users.