Default values for backup's retention policy in docs and code are different

[Michal-Leszczynski]

• Here we can see that default retention policy should be: {retention: 7, retentionDays: 0} - that is also what is stated in backup documentation:
  

  scylla-manager/pkg/command/backup/cmd.go

  Lines 83 to 84 in 87cc888

  	w.Unwrap().IntVar(&cmd.retention, "retention", 7, "")
  	w.Unwrap().IntVar(&cmd.retentionDays, "retention-days", 0, "")

• But later, when creating backup target, its default policy is set to: {retention: 3, retentionDays: 0}.
  

  scylla-manager/pkg/service/backup/model.go

  Lines 243 to 249 in 87cc888

  	func defaultTaskProperties() taskProperties {
  	return taskProperties{
  	Retention: 3,
  	RetentionDays: 0,
  	Continue: true,
  	}
  	}

• Also, Scylla Manager assigns default retention policy for deleted tasks: {retention: 0, retentionDays: 30}.
  

  scylla-manager/pkg/service/backup/service.go

  Lines 87 to 97 in 87cc888

  	// GetRetention returns the retention policy for a
  	// given task ID, with a default of 30 days retention if no policy exists.
  	func GetRetention(taskID uuid.UUID, retentionMap RetentionMap) Retention {
  	r, ok := retentionMap[taskID]
  	if !ok {
  	return Retention{30, 0}
  	}
  	return r
  	}

Q1: What should be the default retention policy for a new task?

Q2: Should Scylla Manager purge backups created by deleted tasks? If yes, then should it still be using (if possible) task's original retention policy or should it use default retention policy for deleted tasks? What should be this default retention policy for deleted tasks?

[Michal-Leszczynski]

@tzach do you know how we should set those default values?

[tzach]

Not with out looking deeper into this.

[karol-kokoszka]

Let use the same values that we put into the documentation
https://manager.docs.scylladb.com/stable/sctool/backup.html#retention
https://manager.docs.scylladb.com/stable/sctool/backup.html#retention-days

retention 7, retention-days 0

Let's inform the end-user about the 30 days retention for the backups made with the deleted task.