diff --git a/server/src/main/java/org/elasticsearch/common/util/concurrent/SizeBlockingQueue.java b/server/src/main/java/org/elasticsearch/common/util/concurrent/SizeBlockingQueue.java
index c4142152ccf..457754d104c 100644
--- a/server/src/main/java/org/elasticsearch/common/util/concurrent/SizeBlockingQueue.java
+++ b/server/src/main/java/org/elasticsearch/common/util/concurrent/SizeBlockingQueue.java
@@ -130,10 +130,14 @@ public class SizeBlockingQueue<E> extends AbstractQueue<E> implements BlockingQu
 
     @Override
     public boolean offer(E e) {
-        int count = size.incrementAndGet();
-        if (count > capacity()) {
-            size.decrementAndGet();
-            return false;
+        while (true) {
+            final int current = size.get();
+            if (current >= capacity()) {
+                return false;
+            }
+            if (size.compareAndSet(current, 1 + current)) {
+                break;
+            }
         }
         boolean offered = queue.offer(e);
         if (!offered) {
diff --git a/server/src/test/java/org/elasticsearch/common/util/concurrent/SizeBlockingQueueTests.java b/server/src/test/java/org/elasticsearch/common/util/concurrent/SizeBlockingQueueTests.java
new file mode 100644
index 00000000000..ebb49c59803
--- /dev/null
+++ b/server/src/test/java/org/elasticsearch/common/util/concurrent/SizeBlockingQueueTests.java
@@ -0,0 +1,94 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.common.util.concurrent;
+
+import org.elasticsearch.test.ESTestCase;
+
+import java.util.concurrent.ArrayBlockingQueue;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.hamcrest.Matchers.equalTo;
+
+public class SizeBlockingQueueTests extends ESTestCase {
+
+    /*
+     * Tests that the size of a queue remains at most the capacity while offers are made to a queue when at capacity. This test would have
+     * previously failed when the size of the queue was incremented and exposed externally even though the item offered to the queue was
+     * never actually added to the queue.
+     */
+    public void testQueueSize() throws InterruptedException {
+        final int capacity = randomIntBetween(1, 32);
+        final BlockingQueue<Integer> blockingQueue = new ArrayBlockingQueue<>(capacity);
+        final SizeBlockingQueue<Integer> sizeBlockingQueue = new SizeBlockingQueue<>(blockingQueue, capacity);
+
+        // fill the queue to capacity
+        for (int i = 0; i < capacity; i++) {
+            sizeBlockingQueue.offer(i);
+        }
+
+        final CountDownLatch latch = new CountDownLatch(1);
+
+        final AtomicBoolean spin = new AtomicBoolean(true);
+        final AtomicInteger maxSize = new AtomicInteger();
+
+        // this thread will repeatedly poll the size of the queue keeping track of the maximum size that it sees
+        final Thread queueSizeThread = new Thread(() -> {
+            try {
+                latch.await();
+            } catch (final InterruptedException e) {
+                throw new RuntimeException(e);
+            }
+            while (spin.get()) {
+                maxSize.set(Math.max(maxSize.get(), sizeBlockingQueue.size()));
+            }
+        });
+        queueSizeThread.start();
+
+        // this thread will try to offer items to the queue while the queue size thread is polling the size
+        final Thread queueOfferThread = new Thread(() -> {
+            try {
+                latch.await();
+            } catch (final InterruptedException e) {
+                throw new RuntimeException(e);
+            }
+            for (int i = 0; i < 4096; i++) {
+                sizeBlockingQueue.offer(capacity + i);
+            }
+        });
+        queueOfferThread.start();
+
+        // synchronize the start of the two threads
+        latch.countDown();
+
+        // wait for the offering thread to finish
+        queueOfferThread.join();
+
+        // stop the queue size thread
+        spin.set(false);
+        queueSizeThread.join();
+
+        // the maximum size of the queue should be equal to the capacity
+        assertThat(maxSize.get(), equalTo(capacity));
+    }
+
+}