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https://issues.apache.org/jira/browse/GEODE-7245?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17287299#comment-17287299
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ASF GitHub Bot commented on GEODE-7245:
---------------------------------------
bschuchardt commented on a change in pull request #6037:
URL: https://github.com/apache/geode/pull/6037#discussion_r579399721
##########
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
*/
private final Map<ID, Object> shutdownMembers = new BoundedLinkedHashMap<>();
Review comment:
I'm wondering if this could be made a synchronized collection with
Collections.synchronizedMap(). Then we could get rid of the external
synchronization.
##########
File path:
geode-membership/src/main/java/org/apache/geode/distributed/internal/membership/gms/GMSMembership.java
##########
@@ -677,10 +658,12 @@ private void removeWithViewLock(ID dm, boolean crashed,
String reason) {
return; // Explicit deletion, no upcall.
}
- if (!shutdownMembers.containsKey(dm)) {
- // if we've received a shutdown message then DistributionManager will
already have
- // notified listeners
- listener.memberDeparted(dm, crashed, reason);
+ 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);
Review comment:
Is it necessary to hold the lock on shutdownMembers while invoking a
listener? The point of this check is to avoid invoking memberDeparted if a
shutdown message from **dm** has already been processed. In that case we've
already invoked memberDeparted on the listener.
##########
File path:
geode-membership/src/main/java/org/apache/geode/distributed/internal/membership/gms/GMSMembership.java
##########
@@ -1524,15 +1487,9 @@ public boolean isShunned(ID m) {
}
private boolean isShunnedOrNew(final ID m) {
- latestViewReadLock.lock();
- try {
- return shunnedMembers.containsKey(m) || isNew(m);
- } finally { // synchronized
- latestViewReadLock.unlock();
- }
+ return shunnedMembers.containsKey(m) || isNew(m);
}
- // must be invoked under view read or write lock
private boolean isNew(final ID m) {
return !latestView.contains(m) && !surpriseMembers.containsKey(m);
Review comment:
I think the read-lock is still needed here. While the "shunned" state
of the member is disconnected from the other two checks, surpriseMembers is
modified while forming a new membership view and we want these two checks to be
atomic.
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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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