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GH-1292 Fix memory leak in PersistentWatcher #1293

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GH-1292 Fix memory leak in PersistentWatcher #1293

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7b7dc92
GH-1292 Fix memory leak in PersistentWatcher
vreuland May 3, 2026
62d9daf
GH-1292 Add test to assert listener leak in PersistentWatcher is fixed
vreuland May 4, 2026
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13 changes: 8 additions & 5 deletions ...r-recipes/src/main/java/org/apache/curator/framework/recipes/watch/PersistentWatcher.java
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,7 @@
import org.apache.curator.framework.api.BackgroundCallback;
import org.apache.curator.framework.api.CuratorClosedException;
import org.apache.curator.framework.api.CuratorEventType;
import org.apache.curator.framework.api.CuratorListener;
import org.apache.curator.framework.imps.CuratorFrameworkBase;
import org.apache.curator.framework.listen.Listenable;
import org.apache.curator.framework.listen.StandardListenerManager;
Expand All @@ -53,6 +54,11 @@ public class PersistentWatcher implements Closeable {
reset();
}
};
private final CuratorListener clientCloseListener = (ignored, event) -> {
if (event.getType() == CuratorEventType.CLOSING) {
onClientClosed();
}
};
private final Watcher watcher = event -> listeners.forEach(w -> w.process(event));
private final CuratorFramework client;
private final String basePath;
Expand Down Expand Up @@ -82,11 +88,7 @@ public void start() {
Preconditions.checkState(state.compareAndSet(State.LATENT, State.STARTED), "Already started");
client.getConnectionStateListenable().addListener(connectionStateListener);
// This could be a namespaced facade which does not support getCuratorListenable.
((CuratorFrameworkBase) client).client().getCuratorListenable().addListener(((ignored, event) -> {
if (event.getType() == CuratorEventType.CLOSING) {
onClientClosed();
}
}));
((CuratorFrameworkBase) client).client().getCuratorListenable().addListener(clientCloseListener);
reset();
}

Expand All @@ -97,6 +99,7 @@ public void start() {
public void close() {
if (state.compareAndSet(State.STARTED, State.CLOSED)) {
listeners.clear();
((CuratorFrameworkBase) client).client().getCuratorListenable().removeListener(clientCloseListener);
client.getConnectionStateListenable().removeListener(connectionStateListener);
try {
client.watchers().remove(watcher).guaranteed().inBackground().forPath(basePath);
Expand Down
19 changes: 19 additions & 0 deletions ...cipes/src/test/java/org/apache/curator/framework/recipes/watch/TestPersistentWatcher.java
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,7 @@
import java.util.concurrent.TimeUnit;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.listen.StandardListenerManager;
import org.apache.curator.framework.state.ConnectionState;
import org.apache.curator.retry.RetryOneTime;
import org.apache.curator.test.compatibility.CuratorTestBase;
Expand Down Expand Up @@ -134,6 +135,24 @@ public void testAfterClientClose() throws Exception {
assertEquals(Watcher.Event.KeeperState.Closed, event.getState());
}

// GH-1292 Curator listener Leak in PersistentWatcher
@Test
public void testCuratorListenersNotLeaking() {
try (CuratorFramework client = CuratorFrameworkFactory.newClient(
server.getConnectString(), timing.session(), timing.connection(), new RetryOneTime(1))) {
client.start();

for (int i = 0; i < 100; i++) {
try (PersistentWatcher persistentWatcher = new PersistentWatcher(client, "/top/main", true)) {
persistentWatcher.start();
}
}

assertEquals(0, ((StandardListenerManager<?>) client.getCuratorListenable()).size(),
"Curator listeners set up by the now closed PersistentWatchers should have been de-registered");
}
}

private void internalTest(boolean recursive) throws Exception {
try (CuratorFramework client = CuratorFrameworkFactory.newClient(
server.getConnectString(), timing.session(), timing.connection(), new RetryOneTime(1))) {
Expand Down