Stephen O'Donnell created HDDS-3221:
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Summary: Refactor SafeModeHandler to use a Notification Interface
Key: HDDS-3221
URL: https://issues.apache.org/jira/browse/HDDS-3221
Project: Hadoop Distributed Data Store
Issue Type: Improvement
Affects Versions: 0.6.0
Reporter: Stephen O'Donnell
Assignee: Stephen O'Donnell
The SafeModeHandler currently accepts several objects which it notifies when
the safe mode status changes.
Each of these object are notified using a different method (there is no
"notification interface") and some of the logic which really belongs in those
objects (ie what to do when safemode goes on or off) is in the safemode classes
rather than in the receiving class.
As we may need to extend safemode somewhat to delay pipeline creation until
sufficient nodes have registered, I think it is worthwhile to refactor this
area to do the following:
1. Introduce a new Interface "SafeModeTransition" which must be implemented by
any object which wants to listen for safemode starting or ending.
{code}
public interface SafeModeTransition {
void handleSafeModeTransition(SCMSafeModeManager.SafeModeStatus status);
}
{code}
2. Pass the SafeModeStatus object over this new interface. That way, we can
extend SafeModeStatus to include more states in the future than just safemode =
true / false.
3. Change the constructor of SafeModeHandler to allow any number of objects to
be registered to make it more flexible going forward.
4. Ensure the logic of what action to take on safemode transition lives within
the notified objects rather than in the Safemode clases.
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