[flink] 02/02: [FLINK-16576][state backends] Do not distribute KeyGroupsStateHandle which contains empty KeyGroupRange

[li...@apache.org]

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commit 792dbf0b72ca8a7ac2cb00d4da3f84c7bfe1b59d
Author: klion26 <qc...@gmail.com>
AuthorDate: Tue Apr 14 12:06:43 2020 +0800

    [FLINK-16576][state backends] Do not distribute KeyGroupsStateHandle which contains empty KeyGroupRange
    
    This closes #11555.
---
 .../flink/runtime/state/KeyGroupsStateHandle.java  |  7 ++-
 .../flink/runtime/state/KeyedStateHandle.java      |  6 ++-
 .../runtime/state/KeyGroupsStateHandleTest.java    | 59 ++++++++++++++++++++++
 3 files changed, 70 insertions(+), 2 deletions(-)

diff --git a/flink-runtime/src/main/java/org/apache/flink/runtime/state/KeyGroupsStateHandle.java b/flink-runtime/src/main/java/org/apache/flink/runtime/state/KeyGroupsStateHandle.java
index 8092f6c..f78ec51 100644
--- a/flink-runtime/src/main/java/org/apache/flink/runtime/state/KeyGroupsStateHandle.java
+++ b/flink-runtime/src/main/java/org/apache/flink/runtime/state/KeyGroupsStateHandle.java
@@ -83,8 +83,13 @@ public class KeyGroupsStateHandle implements StreamStateHandle, KeyedStateHandle
 	 * @return key-group state over a range that is the intersection between this handle's key-group range and the
 	 *          provided key-group range.
 	 */
+	@Override
 	public KeyGroupsStateHandle getIntersection(KeyGroupRange keyGroupRange) {
-		return new KeyGroupsStateHandle(groupRangeOffsets.getIntersection(keyGroupRange), stateHandle);
+		KeyGroupRangeOffsets offsets = groupRangeOffsets.getIntersection(keyGroupRange);
+		if (offsets.getKeyGroupRange().getNumberOfKeyGroups() <= 0) {
+			return null;
+		}
+		return new KeyGroupsStateHandle(offsets, stateHandle);
 	}
 
 	@Override
diff --git a/flink-runtime/src/main/java/org/apache/flink/runtime/state/KeyedStateHandle.java b/flink-runtime/src/main/java/org/apache/flink/runtime/state/KeyedStateHandle.java
index 704ec14..a048aeb 100644
--- a/flink-runtime/src/main/java/org/apache/flink/runtime/state/KeyedStateHandle.java
+++ b/flink-runtime/src/main/java/org/apache/flink/runtime/state/KeyedStateHandle.java
@@ -18,6 +18,8 @@
 
 package org.apache.flink.runtime.state;
 
+import javax.annotation.Nullable;
+
 /**
  * Base for the handles of the checkpointed states in keyed streams. When
  * recovering from failures, the handle will be passed to all tasks whose key
@@ -34,7 +36,9 @@ public interface KeyedStateHandle extends CompositeStateHandle {
 	 * Returns a state over a range that is the intersection between this
 	 * handle's key-group range and the provided key-group range.
 	 *
-	 * @param keyGroupRange The key group range to intersect with
+	 * @param keyGroupRange The key group range to intersect with,
+	 * will return null if the intersection of this handle's key-group and the provided key-group is empty.
 	 */
+	@Nullable
 	KeyedStateHandle getIntersection(KeyGroupRange keyGroupRange);
 }
diff --git a/flink-runtime/src/test/java/org/apache/flink/runtime/state/KeyGroupsStateHandleTest.java b/flink-runtime/src/test/java/org/apache/flink/runtime/state/KeyGroupsStateHandleTest.java
new file mode 100644
index 0000000..ce6bf82
--- /dev/null
+++ b/flink-runtime/src/test/java/org/apache/flink/runtime/state/KeyGroupsStateHandleTest.java
@@ -0,0 +1,59 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF 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.apache.flink.runtime.state;
+
+import org.apache.flink.runtime.state.memory.ByteStreamStateHandle;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+
+/**
+ * A test for {@link KeyGroupsStateHandle}
+ */
+public class KeyGroupsStateHandleTest {
+
+	@Test
+	public void testNonEmptyIntersection() {
+		KeyGroupRangeOffsets offsets = new KeyGroupRangeOffsets(0, 7);
+		byte[] dummy = new byte[10];
+		StreamStateHandle streamHandle = new ByteStreamStateHandle("test", dummy);
+		KeyGroupsStateHandle handle = new KeyGroupsStateHandle(offsets, streamHandle);
+
+		KeyGroupRange expectedRange = new KeyGroupRange(0, 3);
+		KeyGroupsStateHandle newHandle = handle.getIntersection(expectedRange);
+		assertNotNull(newHandle);
+		assertEquals(streamHandle, newHandle.getDelegateStateHandle());
+		assertEquals(expectedRange, newHandle.getKeyGroupRange());
+	}
+
+	@Test
+	public void testEmptyIntersection() {
+		KeyGroupRangeOffsets offsets = new KeyGroupRangeOffsets(0, 7);
+		byte[] dummy = new byte[10];
+		StreamStateHandle streamHandle = new ByteStreamStateHandle("test", dummy);
+		KeyGroupsStateHandle handle = new KeyGroupsStateHandle(offsets, streamHandle);
+		// return null if the the keygroup intersection is empty.
+		KeyGroupRange newRange = new KeyGroupRange(8, 11);
+		assertNull(handle.getIntersection(newRange));
+	}
+}
+