diff --git a/server/src/main/java/org/elasticsearch/common/io/stream/StreamInput.java b/server/src/main/java/org/elasticsearch/common/io/stream/StreamInput.java
index 6ef524ec378..fbc3d9deb92 100644
--- a/server/src/main/java/org/elasticsearch/common/io/stream/StreamInput.java
+++ b/server/src/main/java/org/elasticsearch/common/io/stream/StreamInput.java
@@ -532,6 +532,9 @@ public abstract class StreamInput extends InputStream {
 
     public <K, V> Map<K, V> readMap(Writeable.Reader<K> keyReader, Writeable.Reader<V> valueReader) throws IOException {
         int size = readArraySize();
+        if (size == 0) {
+            return Collections.emptyMap();
+        }
         Map<K, V> map = new HashMap<>(size);
         for (int i = 0; i < size; i++) {
             K key = keyReader.read(this);
@@ -649,6 +652,9 @@ public abstract class StreamInput extends InputStream {
     @SuppressWarnings("unchecked")
     private List readArrayList() throws IOException {
         int size = readArraySize();
+        if (size == 0) {
+            return Collections.emptyList();
+        }
         List list = new ArrayList(size);
         for (int i = 0; i < size; i++) {
             list.add(readGenericValue());
@@ -666,8 +672,13 @@ public abstract class StreamInput extends InputStream {
         return ZonedDateTime.ofInstant(Instant.ofEpochMilli(readLong()), ZoneId.of(timeZoneId));
     }
 
+    private static final Object[] EMPTY_OBJECT_ARRAY = new Object[0];
+
     private Object[] readArray() throws IOException {
         int size8 = readArraySize();
+        if (size8 == 0) {
+            return EMPTY_OBJECT_ARRAY;
+        }
         Object[] list8 = new Object[size8];
         for (int i = 0; i < size8; i++) {
             list8[i] = readGenericValue();
@@ -677,6 +688,9 @@ public abstract class StreamInput extends InputStream {
 
     private Map readLinkedHashMap() throws IOException {
         int size9 = readArraySize();
+        if (size9 == 0) {
+            return Collections.emptyMap();
+        }
         Map map9 = new LinkedHashMap(size9);
         for (int i = 0; i < size9; i++) {
             map9.put(readString(), readGenericValue());
@@ -686,6 +700,9 @@ public abstract class StreamInput extends InputStream {
 
     private Map readHashMap() throws IOException {
         int size10 = readArraySize();
+        if (size10 == 0) {
+            return Collections.emptyMap();
+        }
         Map map10 = new HashMap(size10);
         for (int i = 0; i < size10; i++) {
             map10.put(readString(), readGenericValue());
@@ -738,8 +755,13 @@ public abstract class StreamInput extends InputStream {
         return null;
     }
 
+    private static final int[] EMPTY_INT_ARRAY = new int[0];
+
     public int[] readIntArray() throws IOException {
         int length = readArraySize();
+        if (length == 0) {
+            return EMPTY_INT_ARRAY;
+        }
         int[] values = new int[length];
         for (int i = 0; i < length; i++) {
             values[i] = readInt();
@@ -749,6 +771,9 @@ public abstract class StreamInput extends InputStream {
 
     public int[] readVIntArray() throws IOException {
         int length = readArraySize();
+        if (length == 0) {
+            return EMPTY_INT_ARRAY;
+        }
         int[] values = new int[length];
         for (int i = 0; i < length; i++) {
             values[i] = readVInt();
@@ -756,8 +781,13 @@ public abstract class StreamInput extends InputStream {
         return values;
     }
 
+    private static final long[] EMPTY_LONG_ARRAY = new long[0];
+
     public long[] readLongArray() throws IOException {
         int length = readArraySize();
+        if (length == 0) {
+            return EMPTY_LONG_ARRAY;
+        }
         long[] values = new long[length];
         for (int i = 0; i < length; i++) {
             values[i] = readLong();
@@ -767,6 +797,9 @@ public abstract class StreamInput extends InputStream {
 
     public long[] readVLongArray() throws IOException {
         int length = readArraySize();
+        if (length == 0) {
+            return EMPTY_LONG_ARRAY;
+        }
         long[] values = new long[length];
         for (int i = 0; i < length; i++) {
             values[i] = readVLong();
@@ -774,8 +807,13 @@ public abstract class StreamInput extends InputStream {
         return values;
     }
 
+    private static final float[] EMPTY_FLOAT_ARRAY = new float[0];
+
     public float[] readFloatArray() throws IOException {
         int length = readArraySize();
+        if (length == 0) {
+            return EMPTY_FLOAT_ARRAY;
+        }
         float[] values = new float[length];
         for (int i = 0; i < length; i++) {
             values[i] = readFloat();
@@ -783,8 +821,13 @@ public abstract class StreamInput extends InputStream {
         return values;
     }
 
+    private static final double[] EMPTY_DOUBLE_ARRAY = new double[0];
+
     public double[] readDoubleArray() throws IOException {
         int length = readArraySize();
+        if (length == 0) {
+            return EMPTY_DOUBLE_ARRAY;
+        }
         double[] values = new double[length];
         for (int i = 0; i < length; i++) {
             values[i] = readDouble();
@@ -792,8 +835,13 @@ public abstract class StreamInput extends InputStream {
         return values;
     }
 
+    private static final byte[] EMPTY_BYTE_ARRAY = new byte[0];
+
     public byte[] readByteArray() throws IOException {
         final int length = readArraySize();
+        if (length == 0) {
+            return EMPTY_BYTE_ARRAY;
+        }
         final byte[] bytes = new byte[length];
         readBytes(bytes, 0, bytes.length);
         return bytes;
@@ -983,7 +1031,7 @@ public abstract class StreamInput extends InputStream {
      * @throws IOException if an I/O exception occurs reading the list
      */
     public <T> List<T> readList(final Writeable.Reader<T> reader) throws IOException {
-        return readCollection(reader, ArrayList::new);
+        return readCollection(reader, ArrayList::new, Collections.emptyList());
     }
 
     /**
@@ -1000,15 +1048,19 @@ public abstract class StreamInput extends InputStream {
      * Reads a set of objects
      */
     public <T> Set<T> readSet(Writeable.Reader<T> reader) throws IOException {
-        return readCollection(reader, HashSet::new);
+        return readCollection(reader, HashSet::new, Collections.emptySet());
     }
 
     /**
      * Reads a collection of objects
      */
     private <T, C extends Collection<? super T>> C readCollection(Writeable.Reader<T> reader,
-                                                                  IntFunction<C> constructor) throws IOException {
+                                                                  IntFunction<C> constructor,
+                                                                  C empty) throws IOException {
         int count = readArraySize();
+        if (count == 0) {
+            return empty;
+        }
         C builder = constructor.apply(count);
         for (int i=0; i<count; i++) {
             builder.add(reader.read(this));
@@ -1021,6 +1073,9 @@ public abstract class StreamInput extends InputStream {
      */
     public <T extends NamedWriteable> List<T> readNamedWriteableList(Class<T> categoryClass) throws IOException {
         int count = readArraySize();
+        if (count == 0) {
+            return Collections.emptyList();
+        }
         List<T> builder = new ArrayList<>(count);
         for (int i=0; i<count; i++) {
             builder.add(readNamedWriteable(categoryClass));
diff --git a/server/src/main/java/org/elasticsearch/common/util/concurrent/ThreadContext.java b/server/src/main/java/org/elasticsearch/common/util/concurrent/ThreadContext.java
index 258bf5df1ee..647ef9ff579 100644
--- a/server/src/main/java/org/elasticsearch/common/util/concurrent/ThreadContext.java
+++ b/server/src/main/java/org/elasticsearch/common/util/concurrent/ThreadContext.java
@@ -259,7 +259,31 @@ public final class ThreadContext implements Closeable, Writeable {
      * Reads the headers from the stream into the current context
      */
     public void readHeaders(StreamInput in) throws IOException {
-        threadLocal.set(new ThreadContext.ThreadContextStruct(in));
+        final Map<String, String>  requestHeaders = in.readMap(StreamInput::readString, StreamInput::readString);
+        final Map<String, Set<String>> responseHeaders = in.readMap(StreamInput::readString, input -> {
+            final int size = input.readVInt();
+            if (size == 0) {
+                return Collections.emptySet();
+            } else if (size == 1) {
+                return Collections.singleton(input.readString());
+            } else {
+                // use a linked hash set to preserve order
+                final LinkedHashSet<String> values = new LinkedHashSet<>(size);
+                for (int i = 0; i < size; i++) {
+                    final String value = input.readString();
+                    final boolean added = values.add(value);
+                    assert added : value;
+                }
+                return values;
+            }
+        });
+        final ThreadContextStruct struct;
+        if (requestHeaders.isEmpty() && responseHeaders.isEmpty()) {
+            struct = ThreadContextStruct.EMPTY;
+        } else {
+            struct = new ThreadContextStruct(requestHeaders, responseHeaders, Collections.emptyMap(), false);
+        }
+        threadLocal.set(struct);
     }
 
     /**
@@ -433,40 +457,16 @@ public final class ThreadContext implements Closeable, Writeable {
     }
 
     private static final class ThreadContextStruct {
+
+        private static final ThreadContextStruct EMPTY =
+            new ThreadContextStruct(Collections.emptyMap(), Collections.emptyMap(), Collections.emptyMap(), false);
+
         private final Map<String, String> requestHeaders;
         private final Map<String, Object> transientHeaders;
         private final Map<String, Set<String>> responseHeaders;
         private final boolean isSystemContext;
-        private long warningHeadersSize; //saving current warning headers' size not to recalculate the size with every new warning header
-        private ThreadContextStruct(StreamInput in) throws IOException {
-            final int numRequest = in.readVInt();
-            Map<String, String> requestHeaders = numRequest == 0 ? Collections.emptyMap() : new HashMap<>(numRequest);
-            for (int i = 0; i < numRequest; i++) {
-                requestHeaders.put(in.readString(), in.readString());
-            }
-
-            this.requestHeaders = requestHeaders;
-            this.responseHeaders = in.readMap(StreamInput::readString, input -> {
-                final int size = input.readVInt();
-                if (size == 0) {
-                    return Collections.emptySet();
-                } else if (size == 1) {
-                    return Collections.singleton(input.readString());
-                } else {
-                    // use a linked hash set to preserve order
-                    final LinkedHashSet<String> values = new LinkedHashSet<>(size);
-                    for (int i = 0; i < size; i++) {
-                        final String value = input.readString();
-                        final boolean added = values.add(value);
-                        assert added : value;
-                    }
-                    return values;
-                }
-            });
-            this.transientHeaders = Collections.emptyMap();
-            isSystemContext = false; // we never serialize this it's a transient flag
-            this.warningHeadersSize = 0L;
-        }
+        //saving current warning headers' size not to recalculate the size with every new warning header
+        private final long warningHeadersSize;
 
         private ThreadContextStruct setSystemContext() {
             if (isSystemContext) {
diff --git a/server/src/test/java/org/elasticsearch/search/collapse/CollapseBuilderTests.java b/server/src/test/java/org/elasticsearch/search/collapse/CollapseBuilderTests.java
index 566df804f2b..82c3e261e84 100644
--- a/server/src/test/java/org/elasticsearch/search/collapse/CollapseBuilderTests.java
+++ b/server/src/test/java/org/elasticsearch/search/collapse/CollapseBuilderTests.java
@@ -118,7 +118,7 @@ public class CollapseBuilderTests extends AbstractSerializingTestCase<CollapseBu
         case 2:
         default:
             newBuilder = copyInstance(instance);
-            List<InnerHitBuilder> innerHits = newBuilder.getInnerHits();
+            List<InnerHitBuilder> innerHits = new ArrayList<>(newBuilder.getInnerHits());
             for (int i = 0; i < between(1, 5); i++) {
                 innerHits.add(InnerHitBuilderTests.randomInnerHits());
             }