[GEODE-7245] Remove most uses of latestViewReadLock in GMSMembershipManager

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.14.0, 1.15.0
• Component/s: membership
• Labels: pull-request-available
• Assignee: Kamilla Aslami
• Reporter: Bruce J Schuchardt
• Created: 26/Sep/19 18:29
• Updated: 28/Feb/22 18:35
• Resolved: 02/Mar/21 18:12

Description

Changes for GEODE-7196 made the latestView immutable so there is no reason, in most cases, to use the latestViewReadlock when accessing the view. A simple volatile read of the field & storing the value in a method variable can replace most uses of the latestViewReadLock, especially those uses that are in the path of sending or receiving messages.

Performance could be measured with our benchmarks to see if this change helps.

 

latestViewReadLock is currently used in getCoordinator(), memberExists(), getMembersNotShuttingDown(), getAllMembers(), isShunnedOrNew(), isSurpriseMember(), doWithViewLocked().

doWithViewLocked() is used to add membership listeners, and we don't want the view to change until this operation completes. Therefore, we should keep the lock in this method.

getCoordinator(), memberExists(), getMembersNotShuttingDown(), getAllMembers() use latestViewReadLock to access latestView. In these methods we can replace the lock with a volatile read of the latestView and storing the value in a method variable.

isShunnedOrNew() accesses latestView, and 2 ConcurrentHashMaps - shunnedMembers and surpriseMembers. Since the hashmaps are concurrent and latestView is unmodifiable, a volatile read could replace the lock. Same for isSurpriseMember(), which uses surpriseMembers hashmap.

Issue Links

• causes: GEODE-9350 MemberJoinedEvent should be triggered after new view is installed
• links to: GitHub Pull Request #6037
• links to: GitHub Pull Request #6194