Hi,
When I tested FailureRecovery with GroupLeadershipNotification, I found sometimes the signal was not notified.
As you know, an appropriate recoverer should be selected for FailureRecovery.
But sometimes the recoverer was null when I debugged because of wrong previousView in ViewWindow.java and ViewWindowImpl.java(branch).
The ViewWindow interface has following methods and ViewWindow.java(or ViewWindowImpl.java) implements those.
public interface ViewWindow {
List<GMSMember> getPreviousView();
List<GMSMember> getCurrentView();
...
}
But ViewWindow.java(or ViewWindowImpl.java) returns un-safe lists. See the following code.
In ViewWindow.java
---
public List<GMSMember> getPreviousView() {
List<GMSMember> result = EMPTRY_GMS_MEMBER_LIST;
synchronized(views) {
final int INDEX = views.size() -2;
if(INDEX >= 0) {
// views.get(INDEX) is a List and can be shared unexpectedly.
result = views.get(INDEX);
}
}
return result;
}
...
private void addGroupLeadershipNotificationSignal( ... ) {
...
signals.add( new GroupLeadershipNotificationSignalImpl( token, getPreviousView(), getCurrentView(), ...);
}
---
In GroupLeadershipNotificationSignalImpl.java
---
public void release() throws SignalReleaseException {
if( previousView != null )
previousView.clear();
if( currentView != null )
currentView.clear();
...
}
---
As you see above, sometimes the view(previous or current view) could be shared and cleared unexpectedly by other components.
So I attached proposed patches which copy and return the list safely. And I removed "List.clear()" code in GroupLeadershipNotificationSignalImpl.java because I think the logic is unnecessary.
When I applied the patch, I found it worked well,
Please review the attached patches.
Thanks.
Regards,
Bongjae Chang