Remove close method in PageCacheRecycler/Recycler

The changes in #39317 brought to light some concurrency issues in the
close method of Recyclers as we do not wait for threads running in the
threadpool to be finished prior to the closing of the PageCacheRecycler
and the Recyclers that are used internally. #41695 was opened to
address the concurrent close issues but upon review, the closing of
these classes is not really needed as the instances should be become
available for garbage collection once there is no longer a reference to
the closed node.

Closes #41683

server/src/main/java/org/elasticsearch/client/transport/TransportClient.java

@@ -184,7 +184,6 @@ private static ClientTemplate buildTemplate(Settings providedSettings, Settings
             resourcesToClose.add(circuitBreakerService);
             PageCacheRecycler pageCacheRecycler = new PageCacheRecycler(settings);
             BigArrays bigArrays = new BigArrays(pageCacheRecycler, circuitBreakerService, CircuitBreaker.REQUEST);
-            resourcesToClose.add(pageCacheRecycler);
             modules.add(settingsModule);
             NetworkModule networkModule = new NetworkModule(settings, true, pluginsService.filterPlugins(NetworkPlugin.class), threadPool,
                 bigArrays, pageCacheRecycler, circuitBreakerService, namedWriteableRegistry, xContentRegistry, networkService, null);
@@ -376,7 +375,6 @@ public void close() {
             closeables.add(plugin);
         }
         closeables.add(() -> ThreadPool.terminate(injector.getInstance(ThreadPool.class), 10, TimeUnit.SECONDS));
-        closeables.add(injector.getInstance(PageCacheRecycler.class));
         IOUtils.closeWhileHandlingException(closeables);
     }
 

server/src/main/java/org/elasticsearch/common/recycler/AbstractRecycler.java

@@ -28,9 +28,4 @@ protected AbstractRecycler(Recycler.C<T> c) {
         this.c = c;
     }
 
-    @Override
-    public void close() {
-        // no-op by default
-    }
-
 }

server/src/main/java/org/elasticsearch/common/recycler/ConcurrentDequeRecycler.java

@@ -37,13 +37,6 @@ public ConcurrentDequeRecycler(C<T> c, int maxSize) {
         this.size = new AtomicInteger();
     }
 
-    @Override
-    public void close() {
-        assert deque.size() == size.get();
-        super.close();
-        size.set(0);
-    }
-
     @Override
     public V<T> obtain() {
         final V<T> v = super.obtain();

server/src/main/java/org/elasticsearch/common/recycler/DequeRecycler.java

@@ -36,16 +36,6 @@ public DequeRecycler(C<T> c, Deque<T> queue, int maxSize) {
         this.maxSize = maxSize;
     }
 
-    @Override
-    public void close() {
-        // call destroy() for every cached object
-        for (T t : deque) {
-            c.destroy(t);
-        }
-        // finally get rid of all references
-        deque.clear();
-    }
-
     @Override
     public V<T> obtain() {
         final T v = deque.pollFirst();

server/src/main/java/org/elasticsearch/common/recycler/FilterRecycler.java

@@ -34,9 +34,4 @@ public Recycler.V<T> obtain() {
         return wrap(getDelegate().obtain());
     }
 
-    @Override
-    public void close() {
-        getDelegate().close();
-    }
-
 }

server/src/main/java/org/elasticsearch/common/recycler/NoneRecycler.java

@@ -31,11 +31,6 @@ public V<T> obtain() {
         return new NV<>(c.newInstance());
     }
 
-    @Override
-    public void close() {
-        // no-op
-    }
-
     public static class NV<T> implements Recycler.V<T> {
 
         T value;

server/src/main/java/org/elasticsearch/common/recycler/Recycler.java

@@ -25,7 +25,7 @@
  * A recycled object, note, implementations should support calling obtain and then recycle
  * on different threads.
  */
-public interface Recycler<T> extends Releasable {
+public interface Recycler<T> {
 
     interface Factory<T> {
         Recycler<T> build();
@@ -53,8 +53,6 @@ interface V<T> extends Releasable {
 
     }
 
-    void close();
-
     V<T> obtain();
 
 }

server/src/main/java/org/elasticsearch/common/recycler/Recyclers.java

@@ -145,13 +145,6 @@ protected Recycler<T> getDelegate() {
                 return recyclers[slot()];
             }
 
-            @Override
-            public void close() {
-                for (Recycler<T> recycler : recyclers) {
-                    recycler.close();
-                }
-            }
-
         };
     }
 

server/src/main/java/org/elasticsearch/common/util/PageCacheRecycler.java

@@ -20,8 +20,6 @@
 package org.elasticsearch.common.util;
 
 import org.apache.lucene.util.RamUsageEstimator;
-import org.elasticsearch.common.lease.Releasable;
-import org.elasticsearch.common.lease.Releasables;
 import org.elasticsearch.common.recycler.AbstractRecyclerC;
 import org.elasticsearch.common.recycler.Recycler;
 import org.elasticsearch.common.settings.Setting;
@@ -39,7 +37,7 @@
 import static org.elasticsearch.common.recycler.Recyclers.none;
 
 /** A recycler of fixed-size pages. */
-public class PageCacheRecycler implements Releasable {
+public class PageCacheRecycler {
 
     public static final Setting<Type> TYPE_SETTING =
         new Setting<>("cache.recycler.page.type", Type.CONCURRENT.name(), Type::parse, Property.NodeScope);
@@ -73,11 +71,6 @@ public class PageCacheRecycler implements Releasable {
         NON_RECYCLING_INSTANCE = new PageCacheRecycler(Settings.builder().put(LIMIT_HEAP_SETTING.getKey(), "0%").build());
     }
 
-    @Override
-    public void close() {
-        Releasables.close(true, bytePage, intPage, longPage, objectPage);
-    }
-
     public PageCacheRecycler(Settings settings) {
         final Type type = TYPE_SETTING.get(settings);
         final long limit = LIMIT_HEAP_SETTING.get(settings).getBytes();

server/src/main/java/org/elasticsearch/node/Node.java

@@ -378,7 +378,6 @@ protected Node(
 
             PageCacheRecycler pageCacheRecycler = createPageCacheRecycler(settings);
             BigArrays bigArrays = createBigArrays(pageCacheRecycler, circuitBreakerService);
-            resourcesToClose.add(pageCacheRecycler);
             modules.add(settingsModule);
             List<NamedWriteableRegistry.Entry> namedWriteables = Stream.of(
                 NetworkModule.getNamedWriteables().stream(),
@@ -844,7 +843,6 @@ public synchronized void close() throws IOException {
         toClose.add(() -> stopWatch.stop());
 
         toClose.add(injector.getInstance(NodeEnvironment.class));
-        toClose.add(injector.getInstance(PageCacheRecycler.class));
 
         if (logger.isTraceEnabled()) {
             logger.trace("Close times for each service:\n{}", stopWatch.prettyPrint());

server/src/test/java/org/elasticsearch/common/recycler/AbstractRecyclerTestCase.java

@@ -99,7 +99,6 @@ public void testReuse() {
             assertNotSame(b1, b2);
         }
         o.close();
-        r.close();
     }
 
     public void testRecycle() {
@@ -111,7 +110,6 @@ public void testRecycle() {
         o = r.obtain();
         assertRecycled(o.v());
         o.close();
-        r.close();
     }
 
     public void testDoubleRelease() {
@@ -128,7 +126,6 @@ public void testDoubleRelease() {
         final Recycler.V<byte[]> v2 = r.obtain();
         final Recycler.V<byte[]> v3 = r.obtain();
         assertNotSame(v2.v(), v3.v());
-        r.close();
     }
 
     public void testDestroyWhenOverCapacity() {
@@ -152,9 +149,6 @@ public void testDestroyWhenOverCapacity() {
         // release first ref, verify for destruction
         o.close();
         assertDead(data);
-
-        // close the rest
-        r.close();
     }
 
     public void testClose() {
@@ -171,10 +165,6 @@ public void testClose() {
 
         // verify that recycle() ran
         assertRecycled(data);
-
-        // closing the recycler should mark recycled instances via destroy()
-        r.close();
-        assertDead(data);
     }
 
 }