rkhachatryan commented on a change in pull request #11403: 
[FLINK-16316][operators] Implement new StreamOperatorBase as a replacement for 
AbstractStreamOperator
URL: https://github.com/apache/flink/pull/11403#discussion_r397788433
 
 

 ##########
 File path: 
flink-streaming-java/src/main/java/org/apache/flink/streaming/api/operators/StreamOperatorStateHandler.java
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+/*
+ * 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.streaming.api.operators;
+
+import org.apache.flink.annotation.PublicEvolving;
+import org.apache.flink.annotation.VisibleForTesting;
+import org.apache.flink.api.common.ExecutionConfig;
+import org.apache.flink.api.common.state.KeyedStateStore;
+import org.apache.flink.api.common.state.State;
+import org.apache.flink.api.common.state.StateDescriptor;
+import org.apache.flink.api.common.typeutils.TypeSerializer;
+import org.apache.flink.core.fs.CloseableRegistry;
+import org.apache.flink.core.memory.DataOutputViewStreamWrapper;
+import org.apache.flink.runtime.checkpoint.CheckpointException;
+import org.apache.flink.runtime.checkpoint.CheckpointFailureReason;
+import org.apache.flink.runtime.checkpoint.CheckpointOptions;
+import org.apache.flink.runtime.state.AbstractKeyedStateBackend;
+import org.apache.flink.runtime.state.CheckpointStreamFactory;
+import org.apache.flink.runtime.state.DefaultKeyedStateStore;
+import org.apache.flink.runtime.state.KeyGroupRange;
+import org.apache.flink.runtime.state.KeyGroupStatePartitionStreamProvider;
+import org.apache.flink.runtime.state.KeyGroupsList;
+import org.apache.flink.runtime.state.KeyedStateBackend;
+import org.apache.flink.runtime.state.KeyedStateCheckpointOutputStream;
+import org.apache.flink.runtime.state.OperatorStateBackend;
+import org.apache.flink.runtime.state.StateInitializationContext;
+import org.apache.flink.runtime.state.StateInitializationContextImpl;
+import org.apache.flink.runtime.state.StatePartitionStreamProvider;
+import org.apache.flink.runtime.state.StateSnapshotContext;
+import org.apache.flink.runtime.state.StateSnapshotContextSynchronousImpl;
+import org.apache.flink.runtime.state.VoidNamespaceSerializer;
+import org.apache.flink.streaming.api.watermark.Watermark;
+import org.apache.flink.util.CloseableIterable;
+import org.apache.flink.util.ExceptionUtils;
+import org.apache.flink.util.IOUtils;
+import org.apache.flink.util.function.ThrowingConsumer;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.annotation.Nullable;
+
+import java.io.Closeable;
+import java.io.IOException;
+import java.util.Optional;
+
+/**
+ * Class encapsulating various state backend handling logic for {@link 
StreamOperator} implementations.
+ */
+@PublicEvolving
+public class StreamOperatorStateHandler {
+
+       protected static final Logger LOG = 
LoggerFactory.getLogger(StreamOperatorStateHandler.class);
+
+       /** Backend for keyed state. This might be empty if we're not on a 
keyed stream. */
+       @Nullable
+       private final AbstractKeyedStateBackend<?> keyedStateBackend;
+       private final CloseableRegistry closeableRegistry;
+       @Nullable
+       private final DefaultKeyedStateStore keyedStateStore;
+       private final OperatorStateBackend operatorStateBackend;
+       private final InternalTimeServiceManager<?> timeServiceManager;
+       private final StreamOperatorStateContext context;
+
+       public StreamOperatorStateHandler(
+                       StreamOperatorStateContext context,
+                       ExecutionConfig executionConfig,
+                       CloseableRegistry closeableRegistry) {
+               this.context = context;
+               operatorStateBackend = context.operatorStateBackend();
+               keyedStateBackend = context.keyedStateBackend();
+               this.closeableRegistry = closeableRegistry;
+
+               if (keyedStateBackend != null) {
+                       keyedStateStore = new 
DefaultKeyedStateStore(keyedStateBackend, executionConfig);
+               }
+               else {
+                       keyedStateStore = null;
+               }
+
+               timeServiceManager = context.internalTimerServiceManager();
+       }
+
+       public void 
initializeOperatorState(ThrowingConsumer<StateInitializationContext, Exception> 
initializeOperatorAction) throws Exception {
+               CloseableIterable<KeyGroupStatePartitionStreamProvider> 
keyedStateInputs = context.rawKeyedStateInputs();
+               CloseableIterable<StatePartitionStreamProvider> 
operatorStateInputs = context.rawOperatorStateInputs();
+
+               try {
+                       StateInitializationContext initializationContext = new 
StateInitializationContextImpl(
+                               context.isRestored(), // information whether we 
restore or start for the first time
+                               operatorStateBackend, // access to operator 
state backend
+                               keyedStateStore, // access to keyed state 
backend
+                               keyedStateInputs, // access to keyed state 
stream
+                               operatorStateInputs); // access to operator 
state stream
+
+                       initializeOperatorAction.accept(initializationContext);
+               } finally {
+                       closeFromRegistry(operatorStateInputs, 
closeableRegistry);
+                       closeFromRegistry(keyedStateInputs, closeableRegistry);
+               }
+       }
+
+       private static void closeFromRegistry(Closeable closeable, 
CloseableRegistry registry) {
+               if (registry.unregisterCloseable(closeable)) {
+                       IOUtils.closeQuietly(closeable);
+               }
+       }
+
+       public void dispose() throws Exception {
+
+               Exception exception = null;
+
+               try {
+                       if 
(closeableRegistry.unregisterCloseable(operatorStateBackend)) {
+                               operatorStateBackend.close();
+                       }
+               } catch (Exception e) {
+                       exception = e;
+               }
+
+               try {
+                       if 
(closeableRegistry.unregisterCloseable(keyedStateBackend)) {
+                               keyedStateBackend.close();
+                       }
+               } catch (Exception e) {
+                       exception = ExceptionUtils.firstOrSuppressed(e, 
exception);
+               }
+
+               try {
+                       if (operatorStateBackend != null) {
+                               operatorStateBackend.dispose();
+                       }
+               } catch (Exception e) {
+                       exception = ExceptionUtils.firstOrSuppressed(e, 
exception);
+               }
+
+               try {
+                       if (keyedStateBackend != null) {
+                               keyedStateBackend.dispose();
+                       }
+               } catch (Exception e) {
+                       exception = ExceptionUtils.firstOrSuppressed(e, 
exception);
+               }
+
+               if (exception != null) {
+                       throw exception;
+               }
+       }
+
+       public OperatorSnapshotFutures snapshotState(
+                       ThrowingConsumer<StateSnapshotContext, Exception> 
snapshotStateAction,
+                       String operatorName,
+                       long checkpointId,
+                       long timestamp,
+                       CheckpointOptions checkpointOptions,
+                       CheckpointStreamFactory factory) throws 
CheckpointException {
+               KeyGroupRange keyGroupRange = null != keyedStateBackend ?
+                       keyedStateBackend.getKeyGroupRange() : 
KeyGroupRange.EMPTY_KEY_GROUP_RANGE;
+
+               OperatorSnapshotFutures snapshotInProgress = new 
OperatorSnapshotFutures();
+
+               StateSnapshotContextSynchronousImpl snapshotContext = new 
StateSnapshotContextSynchronousImpl(
+                       checkpointId,
+                       timestamp,
+                       factory,
+                       keyGroupRange,
+                       closeableRegistry);
+
+               return snapshotState(
+                       snapshotStateAction,
+                       operatorName,
+                       checkpointId,
+                       timestamp,
+                       checkpointOptions,
+                       factory,
+                       snapshotInProgress,
+                       snapshotContext);
+       }
+
+       @VisibleForTesting
+       OperatorSnapshotFutures snapshotState(
+                       ThrowingConsumer<StateSnapshotContext, Exception> 
snapshotStateAction,
+                       String operatorName,
+                       long checkpointId,
+                       long timestamp,
+                       CheckpointOptions checkpointOptions,
+                       CheckpointStreamFactory factory,
+                       OperatorSnapshotFutures snapshotInProgress,
+                       StateSnapshotContextSynchronousImpl snapshotContext) 
throws CheckpointException {
+               try {
+                       snapshotState(snapshotContext, operatorName);
+                       snapshotStateAction.accept(snapshotContext);
+
+                       
snapshotInProgress.setKeyedStateRawFuture(snapshotContext.getKeyedStateStreamFuture());
+                       
snapshotInProgress.setOperatorStateRawFuture(snapshotContext.getOperatorStateStreamFuture());
+
+                       if (null != operatorStateBackend) {
+                               
snapshotInProgress.setOperatorStateManagedFuture(
+                                       
operatorStateBackend.snapshot(checkpointId, timestamp, factory, 
checkpointOptions));
+                       }
+
+                       if (null != keyedStateBackend) {
+                               snapshotInProgress.setKeyedStateManagedFuture(
+                                       
keyedStateBackend.snapshot(checkpointId, timestamp, factory, 
checkpointOptions));
+                       }
+               } catch (Exception snapshotException) {
+                       try {
+                               snapshotInProgress.cancel();
+                       } catch (Exception e) {
+                               snapshotException.addSuppressed(e);
+                       }
+
+                       String snapshotFailMessage = "Could not complete 
snapshot " + checkpointId + " for operator " +
+                               operatorName + ".";
+
+                       try {
+                               snapshotContext.closeExceptionally();
+                       } catch (IOException e) {
+                               snapshotException.addSuppressed(e);
+                       }
+                       throw new CheckpointException(snapshotFailMessage, 
CheckpointFailureReason.CHECKPOINT_DECLINED, snapshotException);
+               }
+
+               return snapshotInProgress;
+       }
+
+       /**
+        * Stream operators with state, which want to participate in a snapshot 
need to override this hook method.
+        *
+        * @param context context that provides information and means required 
for taking a snapshot
+        * @param operatorName
+        */
+       public void snapshotState(StateSnapshotContext context, String 
operatorName) throws Exception {
+               final KeyedStateBackend<?> keyedStateBackend = 
getKeyedStateBackend();
+               //TODO all of this can be removed once heap-based timers are 
integrated with RocksDB incremental snapshots
+               if (keyedStateBackend instanceof AbstractKeyedStateBackend &&
+                       ((AbstractKeyedStateBackend<?>) 
keyedStateBackend).requiresLegacySynchronousTimerSnapshots()) {
+
+                       KeyedStateCheckpointOutputStream out;
+
+                       try {
+                               out = context.getRawKeyedOperatorStateOutput();
+                       } catch (Exception exception) {
+                               throw new Exception("Could not open raw keyed 
operator state stream for " +
+                                       operatorName + '.', exception);
+                       }
+
+                       try {
+                               KeyGroupsList allKeyGroups = 
out.getKeyGroupList();
+                               for (int keyGroupIdx : allKeyGroups) {
+                                       out.startNewKeyGroup(keyGroupIdx);
+
+                                       
timeServiceManager.snapshotStateForKeyGroup(
+                                               new 
DataOutputViewStreamWrapper(out), keyGroupIdx);
+                               }
+                       } catch (Exception exception) {
+                               throw new Exception("Could not write timer 
service of " + operatorName +
+                                       " to checkpoint state stream.", 
exception);
+                       } finally {
+                               try {
+                                       out.close();
+                               } catch (Exception closeException) {
+                                       LOG.warn("Could not close raw keyed 
operator state stream for {}. This " +
+                                               "might have prevented deleting 
some state data.", operatorName, closeException);
+                               }
+                       }
+               }
+       }
+
+       public void notifyCheckpointComplete(long checkpointId) throws 
Exception {
+               if (keyedStateBackend != null) {
+                       
keyedStateBackend.notifyCheckpointComplete(checkpointId);
+               }
+       }
+
+       @SuppressWarnings("unchecked")
+       public <K> KeyedStateBackend<K> getKeyedStateBackend() {
+               return (KeyedStateBackend<K>) keyedStateBackend;
+       }
 
 Review comment:
   Summarizing the offline discussion about type parameters:
   1. For `AbstractStreamOperatorV2`, it's unclear whether it's a public API 
for `MultipleInputStreamOperator`s or not. And if it is, then it's unclear 
whether it should reproduce `AbstractStreamOperator` API. But to be on the safe 
side it's better to have the same API (i.e. type parameters on method level, 
not on class).
   1. For `StreamOperatorStateHandler`, this is a trade-off between confusion 
by `extends<Object>`, by method type parameters, unnecessary casts, duplication 
of these casts.  Given that this is reversible, it's better to go with type 
parameters for methods for now as well.
   

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