nfs4: add NFS4Client#addDisposeListener

Motivation:
NFS4Client object might be associated with some non-state resources, like
delegation heuristic queues). Thus when client is disposed due
to being inactive, those resources must be freed.

Modification:
add NFS4Client#addDisposeListener. Add NFS4Client#disposeIgnoreFailures
(as tryToDispose should throw exceptions). Update NFSv4StateHandler to
use NFS4Client#disposeIgnoreFailures.

Result:
A possibility to free non state resources associated with the client.

Acked-by: Paul Millar
Target: master

Author: kofemann

core/src/main/java/org/dcache/nfs/v4/NFS4Client.java

@@ -31,10 +31,12 @@
 
 import java.net.InetSocketAddress;
 import java.security.Principal;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.Iterator;
+import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.atomic.AtomicInteger;
@@ -56,6 +58,8 @@
 import org.dcache.nfs.v4.xdr.verifier4;
 import org.dcache.nfs.util.Opaque;
 
+import javax.annotation.concurrent.GuardedBy;
+
 public class NFS4Client {
 
     private static final Logger _log = LoggerFactory.getLogger(NFS4Client.class);
@@ -195,6 +199,11 @@ from that which the server has previously recorded the client (as
      */
     private final Clock _clock;
 
+    /**
+     * List of listeners to be notified when client is disposed.
+     */
+    private final List<DisposeListener<NFS4Client>> _disposeListeners = new ArrayList<>();
+
     public NFS4Client(NFSv4StateHandler stateHandler, clientid4 clientId, int minorVersion, InetSocketAddress clientAddress, InetSocketAddress localAddress,
             byte[] ownerID, verifier4 verifier, Principal principal, Duration leaseTime, boolean calbackNeeded) {
 
@@ -211,7 +220,7 @@ public NFS4Client(NFSv4StateHandler stateHandler, clientid4 clientId, int minorV
         _leaseTime = leaseTime;
         _callbackNeeded = calbackNeeded;
         _minorVersion = minorVersion;
-	_reclaim_completed = _minorVersion == 0; // no reclaim for NFSv4.0 clients
+        _reclaim_completed = _minorVersion == 0; // no reclaim for NFSv4.0 clients
         _log.debug("New client: {}", this);
     }
 
@@ -480,7 +489,8 @@ public void detachState(NFS4State state) {
         _clientStates.remove(state.stateid());
     }
 
-    private synchronized void drainStates() {
+    @GuardedBy("this")
+    private void drainStates() {
         Iterator<NFS4State> i = _clientStates.values().iterator();
         while (i.hasNext()) {
             NFS4State state = i.next();
@@ -493,8 +503,29 @@ private synchronized void drainStates() {
      * Release resources used by this client if not released yet. Any subsequent
      * call will have no effect.
      */
-    public final void tryDispose() {
+    public synchronized final void tryDispose() throws ChimeraNFSException {
+        drainStates();
+        Iterator<DisposeListener<NFS4Client>> i = _disposeListeners.iterator();
+        while(i.hasNext()) {
+            DisposeListener<NFS4Client> listener = i.next();
+            listener.notifyDisposed(this);
+            i.remove();
+        }
+    }
+
+    /**
+     * Release resources used by this client if not released yet. Ignore any errors.
+     */
+    public synchronized final void disposeIgnoreFailures() {
         drainStates();
+        _disposeListeners.forEach( l -> {
+            try {
+                l.notifyDisposed(NFS4Client.this);
+            } catch (ChimeraNFSException e) {
+                _log.warn("failed to notify client dispose listener {} : {}",l , e.getMessage());
+            }
+        });
+        _disposeListeners.clear();
     }
 
     /**
@@ -572,4 +603,11 @@ public synchronized void releaseOwner(byte[] owner) throws StaleClientidExceptio
             throw new StaleClientidException();
         }
     }
+
+    /**
+     * Add listener to be notified when client is disposed.
+     */
+    synchronized public void addDisposeListener(DisposeListener<NFS4Client> disposeListener) {
+        _disposeListeners.add(disposeListener);
+    }
 }

core/src/main/java/org/dcache/nfs/v4/NFSv4StateHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2009 - 2023 Deutsches Elektronen-Synchroton,
+ * Copyright (c) 2009 - 2025 Deutsches Elektronen-Synchroton,
  * Member of the Helmholtz Association, (DESY), HAMBURG, GERMANY
  *
  * This library is free software; you can redistribute it and/or modify
@@ -165,7 +165,7 @@ public void removeClient(NFS4Client client) {
         } finally {
             _writeLock.unlock();
         }
-        client.tryDispose();
+        client.disposeIgnoreFailures();
     }
 
     private void addClient(NFS4Client newClient) {
@@ -353,7 +353,7 @@ private DeadClientCollector(ClientRecoveryStore clientStore) {
         @Override
         public void notifyExpired(Cache<clientid4, NFS4Client> cache, NFS4Client client) {
             _log.info("Removing expired client: {}", client);
-            client.tryDispose();
+            client.disposeIgnoreFailures();
             clientStore.removeClient(client.getOwnerId());
         }
     }
@@ -387,7 +387,7 @@ public synchronized void wantReclaim(byte[] owner) throws ChimeraNFSException {
     private void drainClients() {
         _clientsByServerId.stream()
                 .forEach(c -> {
-                    c.tryDispose();
+                    c.disposeIgnoreFailures();
                     _clientsByServerId.remove(c.getId());
                 });
     }