[FLINK-3422][streaming] Update tests reliant on hashing

Closes apache#1685

flink-contrib/flink-storm-examples/src/test/java/org/apache/flink/storm/tests/StormFieldsGroupingITCase.java

@@ -21,13 +21,19 @@
 import backtype.storm.topology.TopologyBuilder;
 import backtype.storm.tuple.Fields;
 
+import org.apache.flink.runtime.util.MathUtils;
 import org.apache.flink.storm.api.FlinkLocalCluster;
 import org.apache.flink.storm.api.FlinkTopology;
 import org.apache.flink.storm.tests.operators.FiniteRandomSpout;
 import org.apache.flink.storm.tests.operators.TaskIdBolt;
 import org.apache.flink.storm.util.BoltFileSink;
+import org.apache.flink.streaming.api.datastream.DataStream;
 import org.apache.flink.streaming.util.StreamingProgramTestBase;
 
+/**
+ * This test relies on the hash function used by the {@link DataStream#keyBy}, which is
+ * assumed to be {@link MathUtils#murmurHash}.
+ */
 public class StormFieldsGroupingITCase extends StreamingProgramTestBase {
 
 	private final static String topologyId = "FieldsGrouping Test";
@@ -43,9 +49,9 @@ protected void preSubmit() throws Exception {
 
 	@Override
 	protected void postSubmit() throws Exception {
-		compareResultsByLinesInMemory("4> -1930858313\n" + "4> 1431162155\n" + "4> 1654374947\n"
-				+ "4> -65105105\n" + "3> -1155484576\n" + "3> 1033096058\n" + "3> -1557280266\n"
-				+ "3> -1728529858\n" + "3> -518907128\n" + "3> -252332814", this.resultPath);
+		compareResultsByLinesInMemory("3> -1155484576\n" + "3> 1033096058\n" + "3> -1930858313\n" +
+			"3> 1431162155\n" + "4> -1557280266\n" + "4> -1728529858\n" + "4> 1654374947\n" +
+			"4> -65105105\n" + "4> -518907128\n" + "4> -252332814\n", this.resultPath);
 	}
 
 	@Override

flink-streaming-java/src/test/java/org/apache/flink/streaming/api/IterateTest.java

@@ -462,6 +462,15 @@ public String map2(String value) throws Exception {
 		assertEquals(Arrays.asList("1", "1", "2", "2", "2", "2"), TestSink.collected);
 	}
 
+	/**
+	 * This test relies on the hash function used by the {@link DataStream#keyBy}, which is
+	 * assumed to be {@link MathUtils#murmurHash}.
+	 *
+	 * For the test to pass all FlatMappers must see at least two records in the iteration,
+	 * which can only be achieved if the hashed values of the input keys map to a complete
+	 * congruence system. Given that the test is designed for 3 parallel FlatMapper instances
+	 * keys chosen from the [1,3] range are a suitable choice.
+     */
 	@Test
 	public void testGroupByFeedback() throws Exception {
 		StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();

flink-streaming-java/src/test/java/org/apache/flink/streaming/api/StreamingOperatorsITCase.java

@@ -23,6 +23,7 @@
 import org.apache.flink.api.common.functions.RichMapFunction;
 import org.apache.flink.api.java.tuple.Tuple2;
 import org.apache.flink.core.fs.FileSystem;
+import org.apache.flink.runtime.util.MathUtils;
 import org.apache.flink.streaming.api.collector.selector.OutputSelector;
 import org.apache.flink.streaming.api.datastream.DataStream;
 import org.apache.flink.streaming.api.datastream.SplitStream;
@@ -67,12 +68,13 @@ public void after() throws Exception {
 	 * of Tuple2<Integer, Integer> is created. The stream is grouped according to the first tuple
 	 * value. Each group is folded where the second tuple value is summed up.
 	 *
-	 * @throws Exception
+	 * This test relies on the hash function used by the {@link DataStream#keyBy}, which is
+	 * assumed to be {@link MathUtils#murmurHash}.
 	 */
 	@Test
-	public void testFoldOperation() throws Exception {
+	public void testGroupedFoldOperation() throws Exception {
 		int numElements = 10;
-		int numKeys = 2;
+		final int numKeys = 2;
 
 		StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
 		DataStream<Tuple2<Integer, Integer>> sourceStream = env.addSource(new TupleSource(numElements, numKeys));
@@ -85,17 +87,20 @@ public Integer fold(Integer accumulator, Tuple2<Integer, Integer> value) throws
 					return accumulator + value.f1;
 				}
 			}).map(new RichMapFunction<Integer, Tuple2<Integer, Integer>>() {
+				int key = -1;
 				@Override
 				public Tuple2<Integer, Integer> map(Integer value) throws Exception {
-					return new Tuple2<Integer, Integer>(getRuntimeContext().getIndexOfThisSubtask(), value);
+					if (key == -1){
+						key = MathUtils.murmurHash(value) % numKeys;
+					}
+					return new Tuple2<>(key, value);
 				}
 			}).split(new OutputSelector<Tuple2<Integer, Integer>>() {
 				@Override
 				public Iterable<String> select(Tuple2<Integer, Integer> value) {
 					List<String> output = new ArrayList<>();
 
 					output.add(value.f0 + "");
-
 					return output;
 				}
 			});
@@ -120,7 +125,7 @@ public Integer map(Tuple2<Integer, Integer> value) throws Exception {
 		int counter2 = 0;
 
 		for (int i = 0; i < numElements; i++) {
-			if (i % 2 == 0) {
+			if (MathUtils.murmurHash(i) % numKeys == 0) {
 				counter1 += i;
 				builder1.append(counter1 + "\n");
 			} else {
@@ -196,7 +201,7 @@ public NonSerializableTupleSource(int numElements) {
 		@Override
 		public void run(SourceContext<Tuple2<Integer, NonSerializable>> ctx) throws Exception {
 			for (int i = 0; i < numElements; i++) {
-				ctx.collect(new Tuple2<Integer, NonSerializable>(i, new NonSerializable(i)));
+				ctx.collect(new Tuple2<>(i, new NonSerializable(i)));
 			}
 		}
 
@@ -217,14 +222,13 @@ public TupleSource(int numElements, int numKeys) {
 		@Override
 		public void run(SourceContext<Tuple2<Integer, Integer>> ctx) throws Exception {
 			for (int i = 0; i < numElements; i++) {
-				Tuple2<Integer, Integer> result = new Tuple2<>(i % numKeys, i);
+				Tuple2<Integer, Integer> result = new Tuple2<>(MathUtils.murmurHash(i) % numKeys, i);
 				ctx.collect(result);
 			}
 		}
 
 		@Override
 		public void cancel() {
-
 		}
 	}
 }

flink-streaming-scala/src/test/scala/org/apache/flink/streaming/api/scala/StreamingOperatorsITCase.scala

@@ -58,9 +58,11 @@ class StreamingOperatorsITCase extends ScalaStreamingMultipleProgramsTestBase {
     * The stream is grouped by the first field. For each group, the resulting stream is folded by
     * summing up the second tuple field.
     *
+    * This test relies on the hash function used by the {@link DataStream#keyBy}, which is
+    * assumed to be {@link MathUtils#murmurHash}.
     */
   @Test
-  def testFoldOperator(): Unit = {
+  def testGroupedFoldOperator(): Unit = {
     val numElements = 10
     val numKeys = 2