muse-dev[bot] commented on a change in pull request #1962:
URL: https://github.com/apache/lucene-solr/pull/1962#discussion_r516960732
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File path:
solr/core/src/java/org/apache/solr/cluster/events/ClusterEventProducerBase.java
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@@ -0,0 +1,85 @@
+package org.apache.solr.cluster.events;
+
+import org.apache.solr.core.CoreContainer;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.lang.invoke.MethodHandles;
+import java.util.Collections;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ *
+ */
+public abstract class ClusterEventProducerBase implements ClusterEventProducer
{
+ private static final Logger log =
LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());
+
+ protected final Map<ClusterEvent.EventType, Set<ClusterEventListener>>
listeners = new ConcurrentHashMap<>();
+ protected volatile State state = State.STOPPED;
+ protected final CoreContainer cc;
+
+ protected ClusterEventProducerBase(CoreContainer cc) {
+ this.cc = cc;
+ }
+
+ @Override
+ public void registerListener(ClusterEventListener listener,
ClusterEvent.EventType... eventTypes) {
+ if (eventTypes == null || eventTypes.length == 0) {
+ eventTypes = ClusterEvent.EventType.values();
+ }
+ for (ClusterEvent.EventType type : eventTypes) {
+ if (!getSupportedEventTypes().contains(type)) {
+ log.warn("event type {} not supported yet.", type);
+ continue;
+ }
+ // to avoid removing no-longer empty set in unregister
+ synchronized (listeners) {
+ listeners.computeIfAbsent(type, t -> ConcurrentHashMap.newKeySet())
+ .add(listener);
+ }
+ }
+ }
+
+ @Override
+ public void unregisterListener(ClusterEventListener listener,
ClusterEvent.EventType... eventTypes) {
+ if (eventTypes == null || eventTypes.length == 0) {
+ eventTypes = ClusterEvent.EventType.values();
+ }
+ synchronized (listeners) {
+ for (ClusterEvent.EventType type : eventTypes) {
+ Set<ClusterEventListener> perType = listeners.get(type);
+ if (perType != null) {
+ perType.remove(listener);
+ if (perType.isEmpty()) {
+ listeners.remove(type);
+ }
+ }
+ }
+ }
+ }
+
+ @Override
+ public State getState() {
+ return state;
+ }
+
+ public Map<ClusterEvent.EventType, Set<ClusterEventListener>>
getEventListeners() {
+ return listeners;
+ }
+
+ public CoreContainer getCoreContainer() {
+ return cc;
+ }
+
+ public abstract Set<ClusterEvent.EventType> getSupportedEventTypes();
+
+ protected void fireEvent(ClusterEvent event) {
+ listeners.getOrDefault(event.getType(), Collections.emptySet())
Review comment:
*THREAD_SAFETY_VIOLATION:* Read/Write race. Non-private method
`ClusterEventProducerBase.fireEvent(...)` reads without synchronization from
container `this.listeners` via call to `Map.getOrDefault(...)`. Potentially
races with write in method `ClusterEventProducerBase.unregisterListener(...)`.
Reporting because another access to the same memory occurs on a background
thread, although this access may not.
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