[GitHub] [flink-ml] guoweiM commented on a change in pull request #8: [FLINK-4][iteration] Add operator wrapper for all-round iterations.

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

guoweiM commented on a change in pull request #8:
URL: https://github.com/apache/flink-ml/pull/8#discussion_r733358268



##########
File path: flink-ml-iteration/src/main/java/org/apache/flink/iteration/progresstrack/OperatorEpochWatermarkTracker.java
##########
@@ -0,0 +1,145 @@
+/*
+ * 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.progresstrack;
+
+import org.apache.flink.annotation.VisibleForTesting;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import static org.apache.flink.util.Preconditions.checkNotNull;
+import static org.apache.flink.util.Preconditions.checkState;
+
+/**
+ * Tracks the epoch watermark from each input. Once the minimum epoch watermark changed, it would
+ * notify the listener.
+ */
+public class OperatorEpochWatermarkTracker {
+
+    private final OperatorEpochWatermarkTrackerListener progressTrackerListener;
+
+    private final List<InputStatus> inputStatuses;
+
+    private final LowerBoundMaintainer allInputsLowerBound;
+
+    public OperatorEpochWatermarkTracker(
+            int[] numberOfChannels, OperatorEpochWatermarkTrackerListener progressTrackerListener) {
+        checkState(numberOfChannels != null && numberOfChannels.length >= 1);
+        this.progressTrackerListener = checkNotNull(progressTrackerListener);
+
+        this.inputStatuses = new ArrayList<>(numberOfChannels.length);
+        for (int numberOfChannel : numberOfChannels) {
+            inputStatuses.add(new InputStatus(numberOfChannel));
+        }
+
+        this.allInputsLowerBound = new LowerBoundMaintainer(numberOfChannels.length);
+    }
+
+    public void onEpochWatermark(int inputIndex, String sender, int epochWatermark)
+            throws IOException {
+        InputStatus inputStatus = inputStatuses.get(inputIndex);
+        inputStatus.onUpdate(sender, epochWatermark);
+
+        if (inputStatus.getInputLowerBound() > allInputsLowerBound.getValue(inputIndex)) {
+            int oldLowerBound = allInputsLowerBound.getLowerBound();
+            allInputsLowerBound.updateValue(inputIndex, inputStatus.getInputLowerBound());
+            if (allInputsLowerBound.getLowerBound() > oldLowerBound) {
+                progressTrackerListener.onEpochWatermarkIncrement(
+                        allInputsLowerBound.getLowerBound());
+            }
+        }
+    }
+
+    @VisibleForTesting
+    int[] getNumberOfInputs() {

Review comment:
       I am not very sure but maybe we could remove this method, which just test the internal implementation.
   What is in my mind is that we could test the `OperatorEpochWatermarkTrackerListener`.

##########
File path: flink-ml-iteration/src/main/java/org/apache/flink/iteration/EpochAware.java
##########
@@ -0,0 +1,30 @@
+/*
+ * 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 java.util.function.Supplier;
+
+/**

Review comment:
       I would suggest to describe the difference between this interface and `IterationListener` more in the document, and why this can't be put in the original Udf/operator's `Context`. 
   I think this might be better to let user understand the semantics of this interface.

##########
File path: flink-ml-iteration/src/main/java/org/apache/flink/iteration/operator/AbstractWrapperOperator.java
##########
@@ -0,0 +1,164 @@
+/*
+ * 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.operator;
+
+import org.apache.flink.iteration.IterationRecord;
+import org.apache.flink.iteration.broadcast.BroadcastOutput;
+import org.apache.flink.iteration.broadcast.BroadcastOutputFactory;
+import org.apache.flink.iteration.progresstrack.OperatorEpochWatermarkTracker;
+import org.apache.flink.iteration.progresstrack.OperatorEpochWatermarkTrackerFactory;
+import org.apache.flink.iteration.progresstrack.OperatorEpochWatermarkTrackerListener;
+import org.apache.flink.iteration.proxy.ProxyOutput;
+import org.apache.flink.runtime.execution.Environment;
+import org.apache.flink.runtime.metrics.groups.InternalOperatorMetricGroup;
+import org.apache.flink.runtime.metrics.groups.UnregisteredMetricGroups;
+import org.apache.flink.streaming.api.graph.StreamConfig;
+import org.apache.flink.streaming.api.operators.Output;
+import org.apache.flink.streaming.api.operators.StreamOperator;
+import org.apache.flink.streaming.api.operators.StreamOperatorFactory;
+import org.apache.flink.streaming.api.operators.StreamOperatorParameters;
+import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
+import org.apache.flink.streaming.runtime.tasks.StreamTask;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.Objects;
+import java.util.function.Supplier;
+
+import static org.apache.flink.util.Preconditions.checkState;
+
+/** The base class of all the wrapper operators. It provides the alignment functionality. */
+public abstract class AbstractWrapperOperator<T>
+        implements StreamOperator<IterationRecord<T>>, OperatorEpochWatermarkTrackerListener {
+
+    private static final Logger LOG = LoggerFactory.getLogger(AbstractWrapperOperator.class);
+
+    protected final StreamOperatorParameters<IterationRecord<T>> parameters;
+
+    protected final StreamConfig streamConfig;
+
+    protected final StreamTask<?, ?> containingTask;
+
+    protected final Output<StreamRecord<IterationRecord<T>>> output;
+
+    protected final StreamOperatorFactory<T> operatorFactory;
+
+    // --------------- proxy ---------------------------
+
+    protected final ProxyOutput<T> proxyOutput;
+
+    protected final EpochSupplier epochWatermarkSupplier;
+
+    // --------------- Metrics ---------------------------
+
+    /** Metric group for the operator. */
+    protected final InternalOperatorMetricGroup metrics;
+
+    // ------------- Iteration Related --------------------
+
+    protected final OperatorEpochWatermarkTracker epochWatermarkTracker;
+
+    protected final String uniqueSenderId;

Review comment:
       Why would we use the string as a id here ? 

##########
File path: flink-ml-iteration/src/main/java/org/apache/flink/iteration/proxy/ProxyOutput.java
##########
@@ -0,0 +1,111 @@
+/*
+ * 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.proxy;
+
+import org.apache.flink.iteration.IterationRecord;
+import org.apache.flink.iteration.typeinfo.IterationRecordTypeInfo;
+import org.apache.flink.streaming.api.operators.Output;
+import org.apache.flink.streaming.api.watermark.Watermark;
+import org.apache.flink.streaming.runtime.streamrecord.LatencyMarker;
+import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
+import org.apache.flink.streaming.runtime.watermarkstatus.WatermarkStatus;
+import org.apache.flink.util.OutputTag;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+
+/** Proxy output to provide to the wrapped operator. */
+public class ProxyOutput<T> implements Output<StreamRecord<T>> {
+
+    private final Output<StreamRecord<IterationRecord<T>>> output;
+
+    private final StreamRecord<IterationRecord<T>> reuseRecord;
+
+    private final Map<String, SideOutputCache> sideOutputCaches = new HashMap<>();
+
+    private Integer contextRound;
+
+    public ProxyOutput(Output<StreamRecord<IterationRecord<T>>> output) {
+        this.output = Objects.requireNonNull(output);
+        this.reuseRecord = new StreamRecord<>(IterationRecord.newRecord(null, 0));
+    }
+
+    public void setContextRound(Integer contextRound) {
+        this.contextRound = contextRound;
+    }
+
+    @Override
+    public void emitWatermark(Watermark mark) {
+        output.emitWatermark(mark);
+    }
+
+    @Override
+    public void emitWatermarkStatus(WatermarkStatus watermarkStatus) {
+        output.emitWatermarkStatus(watermarkStatus);
+    }
+
+    @Override
+    @SuppressWarnings({"unchecked", "rawtypes"})
+    public <X> void collect(OutputTag<X> outputTag, StreamRecord<X> record) {
+        SideOutputCache sideOutputCache =
+                sideOutputCaches.computeIfAbsent(
+                        outputTag.getId(),
+                        (ignored) ->
+                                new SideOutputCache(
+                                        new OutputTag<IterationRecord<?>>(
+                                                outputTag.getId(),
+                                                new IterationRecordTypeInfo(
+                                                        outputTag.getTypeInfo())),
+                                        new StreamRecord<>(IterationRecord.newRecord(null, 0))));
+        sideOutputCache.cachedRecord.replace(
+                IterationRecord.newRecord(record.getValue(), contextRound), record.getTimestamp());
+        output.collect(sideOutputCache.tag, sideOutputCache.cachedRecord);
+    }
+
+    @Override
+    public void emitLatencyMarker(LatencyMarker latencyMarker) {
+        output.emitLatencyMarker(latencyMarker);
+    }
+
+    @Override
+    public void collect(StreamRecord<T> tStreamRecord) {

Review comment:
       tStreamRecord or streamRecord?




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