[GitHub] [flink-ml] gaoyunhaii commented on a change in pull request #12: [FLINK-24650][iteration] add unbounded iteration.

[GitBox <gi...@apache.org>]

gaoyunhaii commented on a change in pull request #12:
URL: https://github.com/apache/flink-ml/pull/12#discussion_r739599530



##########
File path: flink-ml-iteration/src/main/java/org/apache/flink/iteration/IterationFactory.java
##########
@@ -0,0 +1,248 @@
+/*
+ * 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.iteration;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+import org.apache.flink.iteration.compile.DraftExecutionEnvironment;
+import org.apache.flink.iteration.operator.HeadOperatorFactory;
+import org.apache.flink.iteration.operator.InputOperator;
+import org.apache.flink.iteration.operator.OperatorWrapper;
+import org.apache.flink.iteration.operator.OutputOperator;
+import org.apache.flink.iteration.operator.TailOperator;
+import org.apache.flink.iteration.typeinfo.IterationRecordTypeInfo;
+import org.apache.flink.streaming.api.datastream.DataStream;
+import org.apache.flink.streaming.api.datastream.SingleOutputStreamOperator;
+import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
+import org.apache.flink.streaming.api.transformations.OneInputTransformation;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+
+import static org.apache.flink.util.Preconditions.checkState;
+
+/** Creates iteration in a job. */
+@Internal
+public class IterationFactory {
+
+    @SuppressWarnings({"unchecked", "rawtypes"})
+    public static DataStreamList createIteration(
+            DataStreamList initVariableStreams,
+            DataStreamList dataStreams,
+            IterationBody body,
+            OperatorWrapper<?, IterationRecord<?>> initialOperatorWrapper,
+            boolean mayHaveCriteria) {
+        checkState(initVariableStreams.size() > 0, "There should be at least one variable stream");
+
+        IterationID iterationId = new IterationID();
+
+        List<TypeInformation<?>> initVariableTypeInfos = getTypeInfos(initVariableStreams);
+        List<TypeInformation<?>> dataStreamTypeInfos = getTypeInfos(dataStreams);
+
+        // Add heads and inputs
+        int totalInitVariableParallelism =
+                map(initVariableStreams, DataStream::getParallelism).stream()
+                        .mapToInt(i -> i)
+                        .sum();
+        DataStreamList initVariableInputs = addInputs(initVariableStreams, false);
+        DataStreamList headStreams =
+                addHeads(
+                        initVariableStreams,
+                        initVariableInputs,
+                        iterationId,
+                        totalInitVariableParallelism,
+                        false,
+                        0);
+
+        DataStreamList dataStreamInputs = addInputs(dataStreams, true);
+
+        // Create the iteration body.
+        StreamExecutionEnvironment env = initVariableStreams.get(0).getExecutionEnvironment();
+        DraftExecutionEnvironment draftEnv =
+                new DraftExecutionEnvironment(env, initialOperatorWrapper);
+        DataStreamList draftHeadStreams =
+                addDraftSources(headStreams, draftEnv, initVariableTypeInfos);
+        DataStreamList draftDataStreamInputs =
+                addDraftSources(dataStreamInputs, draftEnv, dataStreamTypeInfos);
+
+        IterationBodyResult iterationBodyResult =
+                body.process(draftHeadStreams, draftDataStreamInputs);
+        ensuresTransformationAdded(iterationBodyResult.getFeedbackVariableStreams(), draftEnv);

Review comment:
       Currently flink only adds transformation with operators into the env. Some transformations like `SideOutTransformation` would not be added, but might be used as the return values of the iteration body.




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