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https://issues.apache.org/jira/browse/GEODE-7245?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17287286#comment-17287286
]
ASF GitHub Bot commented on GEODE-7245:
---------------------------------------
Bill commented on a change in pull request #6037:
URL: https://github.com/apache/geode/pull/6037#discussion_r579391765
##########
File path:
geode-membership/src/main/java/org/apache/geode/distributed/internal/membership/gms/GMSMembership.java
##########
@@ -273,6 +273,9 @@ boolean isDistributionMessage() {
/**
* Members that have sent a shutdown message. This is used to suppress
suspect processing that
* otherwise becomes pretty aggressive when a member is shutting down.
+ *
+ * Accesses to this map should be synchronized on the map to avoid concurrent
+ * modification exceptions
Review comment:
Since we only ever `shutdownMembers.put(id, id)` this can be a
`Set<ID>`. It needn't be a map.
Furthermore, if we made it a concurrent map-based set, we could eliminate
all the synchronization below.
This declaration could become:
```
private final Set<ID> shutdownMembers = ConcurrentHashMap.newKeySet();
```
Then code below like this:
```
synchronized (shutdownMembers) {
if (!shutdownMembers.containsKey(dm)) {
// if we've received a shutdown message then DistributionManager
will already have
// notified listeners
listener.memberDeparted(dm, crashed, reason);
}
}
```
changes to this:
```
if (!shutdownMembers.contains(dm)) {
// if we've received a shutdown message then DistributionManager
will already have
// notified listeners
listener.memberDeparted(dm, crashed, reason);
}
```
and code below like this:
```
synchronized (shutdownMembers) {
return latestView.getMembers().stream().filter(id ->
!shutdownMembers.containsKey(id))
.collect(
Collectors.toSet());
}
```
changes to code like this:
```
final Set<ID> membersNotShuttingDown = new
HashSet<ID>(latestView.getMembers());
final Set<ID> shutdownMembersStable = this.shutdownMembers;
membersNotShuttingDown.removeIf(shutdownMembersStable::contains);
return membersNotShuttingDown;
```
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> Remove most uses of latestViewReadLock in GMSMembershipManager
> --------------------------------------------------------------
>
> Key: GEODE-7245
> URL: https://issues.apache.org/jira/browse/GEODE-7245
> Project: Geode
> Issue Type: Improvement
> Components: membership
> Reporter: Bruce J Schuchardt
> Priority: Major
> Labels: pull-request-available
>
> 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.
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