Optimize some Spots around Closing Resources (#60049) (#60096)

The single element `close` calls go through a very inefficient path that includes creating
a one element list.
`releaseOnce` is only with a single non-null input in production in two spots so no need for
varargs and any complexity here.
`ReleasableBytesStreamOutput` does not require any `releaseOnce` wrapping because we already have
that kind of logic implemented in `org.elasticsearch.common.util.AbstractArray` (which we were
wrapping here) already.

libs/core/src/main/java/org/elasticsearch/core/internal/io/IOUtils.java

@@ -19,6 +19,8 @@
 
 package org.elasticsearch.core.internal.io;
 
+import org.elasticsearch.common.Nullable;
+
 import java.io.Closeable;
 import java.io.IOException;
 import java.nio.channels.FileChannel;
@@ -64,6 +66,15 @@ public final class IOUtils {
         close(null, Arrays.asList(objects));
     }
 
+    /**
+     * @see #close(Closeable...)
+     */
+    public static void close(@Nullable Closeable closeable) throws IOException {
+        if (closeable != null) {
+            closeable.close();
+        }
+    }
+
     /**
      * Closes all given {@link Closeable}s. Some of the {@linkplain Closeable}s may be null; they are
      * ignored. After everything is closed, the method adds any exceptions as suppressed to the
@@ -102,9 +113,7 @@ public final class IOUtils {
         Exception firstException = ex;
         for (final Closeable object : objects) {
             try {
-                if (object != null) {
-                    object.close();
-                }
+                close(object);
             } catch (final IOException | RuntimeException e) {
                 if (firstException == null) {
                     firstException = e;
@@ -142,14 +151,18 @@ public final class IOUtils {
      */
     public static void closeWhileHandlingException(final Iterable<? extends Closeable> objects) {
         for (final Closeable object : objects) {
-            // noinspection EmptyCatchBlock
-            try {
-                if (object != null) {
-                    object.close();
-                }
-            } catch (final IOException | RuntimeException e) {
+           closeWhileHandlingException(object);
+        }
+    }
 
-            }
+    /**
+     * @see #closeWhileHandlingException(Closeable...)
+     */
+    public static void closeWhileHandlingException(final Closeable closeable) {
+        // noinspection EmptyCatchBlock
+        try {
+            close(closeable);
+        } catch (final IOException | RuntimeException e) {
         }
     }
 

server/src/main/java/org/elasticsearch/common/io/stream/ReleasableBytesStreamOutput.java

@@ -21,9 +21,7 @@ package org.elasticsearch.common.io.stream;
 
 import org.elasticsearch.common.bytes.ReleasableBytesReference;
 import org.elasticsearch.common.lease.Releasable;
-import org.elasticsearch.common.lease.Releasables;
 import org.elasticsearch.common.util.BigArrays;
-import org.elasticsearch.common.util.ByteArray;
 import org.elasticsearch.common.util.PageCacheRecycler;
 
 /**
@@ -35,10 +33,7 @@ import org.elasticsearch.common.util.PageCacheRecycler;
  * stream should only be closed after the bytes have been output or copied
  * elsewhere.
  */
-public class ReleasableBytesStreamOutput extends BytesStreamOutput
-    implements Releasable {
-
-    private Releasable releasable;
+public class ReleasableBytesStreamOutput extends BytesStreamOutput implements Releasable {
 
     public ReleasableBytesStreamOutput(BigArrays bigarrays) {
         this(PageCacheRecycler.PAGE_SIZE_IN_BYTES, bigarrays);
@@ -46,31 +41,10 @@ public class ReleasableBytesStreamOutput extends BytesStreamOutput
 
     public ReleasableBytesStreamOutput(int expectedSize, BigArrays bigArrays) {
         super(expectedSize, bigArrays);
-        this.releasable = Releasables.releaseOnce(this.bytes);
     }
 
     @Override
     public void close() {
-        Releasables.close(releasable);
-    }
-
-    @Override
-    void ensureCapacity(long offset) {
-        final ByteArray prevBytes = this.bytes;
-        super.ensureCapacity(offset);
-        if (prevBytes != this.bytes) {
-            // re-create the releasable with the new reference
-            releasable = Releasables.releaseOnce(this.bytes);
-        }
-    }
-
-    @Override
-    public void reset() {
-        final ByteArray prevBytes = this.bytes;
-        super.reset();
-        if (prevBytes != this.bytes) {
-            // re-create the releasable with the new reference
-            releasable = Releasables.releaseOnce(this.bytes);
-        }
+        bytes.close();
     }
 }

server/src/main/java/org/elasticsearch/common/lease/Releasables.java

@@ -96,13 +96,13 @@ public enum Releasables {
     }
 
     /**
-     * Equivalent to {@link #wrap(Releasable...)} but can be called multiple times without double releasing.
+     * Wraps a {@link Releasable} such that its {@link Releasable#close()} method can be called multiple times without double releasing.
      */
-    public static Releasable releaseOnce(final Releasable... releasables) {
+    public static Releasable releaseOnce(final Releasable releasable) {
         final AtomicBoolean released = new AtomicBoolean(false);
         return () -> {
             if (released.compareAndSet(false, true)) {
-                close(releasables);
+                releasable.close();
             }
         };
     }

server/src/test/java/org/elasticsearch/common/ReleasablesTests.java

@@ -28,11 +28,11 @@ public class ReleasablesTests extends ESTestCase {
 
     public void testReleaseOnce() {
         AtomicInteger count = new AtomicInteger(0);
-        Releasable releasable = Releasables.releaseOnce(count::incrementAndGet, count::incrementAndGet);
+        Releasable releasable = Releasables.releaseOnce(count::incrementAndGet);
         assertEquals(0, count.get());
         releasable.close();
-        assertEquals(2, count.get());
+        assertEquals(1, count.get());
         releasable.close();
-        assertEquals(2, count.get());
+        assertEquals(1, count.get());
     }
 }