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From tillrohrmann <...@git.apache.org>
Subject [GitHub] flink pull request: [FLINK-3332] Cassandra connector
Date Thu, 11 Feb 2016 17:00:24 GMT
Github user tillrohrmann commented on a diff in the pull request:

    https://github.com/apache/flink/pull/1620#discussion_r52631298
  
    --- Diff: flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/operators/GenericExactlyOnceSink.java
---
    @@ -0,0 +1,173 @@
    +/**
    + * 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
    + * <p/>
    + * http://www.apache.org/licenses/LICENSE-2.0
    + * <p/>
    + * 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.runtime.operators;
    +
    +import org.apache.flink.api.common.ExecutionConfig;
    +import org.apache.flink.api.common.typeinfo.TypeInformation;
    +import org.apache.flink.api.common.typeutils.TypeSerializer;
    +import org.apache.flink.api.java.tuple.Tuple;
    +import org.apache.flink.api.java.typeutils.TypeExtractor;
    +import org.apache.flink.core.memory.DataInputView;
    +import org.apache.flink.runtime.state.AbstractStateBackend;
    +import org.apache.flink.runtime.state.StateHandle;
    +import org.apache.flink.streaming.api.operators.AbstractStreamOperator;
    +import org.apache.flink.streaming.api.operators.OneInputStreamOperator;
    +import org.apache.flink.streaming.api.watermark.Watermark;
    +import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
    +import org.apache.flink.streaming.runtime.tasks.StreamTaskState;
    +
    +import java.io.IOException;
    +import java.io.Serializable;
    +import java.util.ArrayList;
    +import java.util.HashMap;
    +import java.util.HashSet;
    +import java.util.List;
    +import java.util.Set;
    +
    +/**
    + * Generic Sink that emits its input elements into an arbitrary backend. This sink is
integrated with the checkpointing
    + * mechanism to provide exactly once semantics.
    + *
    + * Incoming records are stored within a {@link org.apache.flink.runtime.state.AbstractStateBackend},
and only committed if a
    + * checkpoint is completed. Should a job fail while the data is being committed, no exactly
once guarantee can be made.
    + * @param <IN>
    + */
    +public abstract class GenericExactlyOnceSink<IN extends Tuple> extends AbstractStreamOperator<IN>
implements OneInputStreamOperator<IN, IN> {
    +	private AbstractStateBackend.CheckpointStateOutputView out;
    +	private TypeSerializer<IN> serializer;
    +	protected TypeInformation<IN> typeInfo;
    +
    +	private ExactlyOnceState state = new ExactlyOnceState();
    +
    +	/**
    +	 * Saves a handle in the state.
    +	 * @param checkpointId
    +	 * @throws IOException
    +	 */
    +	private void saveHandleInState(final long checkpointId) throws IOException {
    +		//only add handle if a new OperatorState was created since the last snapshot/notify
    +		if (out != null) {
    +			out.writeByte(0); //EOF-byte
    +			StateHandle<DataInputView> handle = out.closeAndGetHandle();
    +			if (state.pendingHandles.containsKey(checkpointId)) {
    +				state.pendingHandles.get(checkpointId).add(handle);
    +			} else {
    +				ArrayList<StateHandle<DataInputView>> list = new ArrayList<>();
    +				list.add(handle);
    +				state.pendingHandles.put(checkpointId, list);
    +			}
    +			out = null;
    +		}
    +	}
    +
    +	@Override
    +	public StreamTaskState snapshotOperatorState(final long checkpointId, final long timestamp)
throws Exception {
    +		StreamTaskState taskState = super.snapshotOperatorState(checkpointId, timestamp);
    +		saveHandleInState(checkpointId);
    +		taskState.setFunctionState(state);
    +		return taskState;
    +	}
    +
    +	@Override
    +	public void restoreState(StreamTaskState state, long recoveryTimestamp) throws Exception
{
    +		super.restoreState(state, recoveryTimestamp);
    +		this.state = (ExactlyOnceState) state.getFunctionState();
    +		out = null;
    +	}
    +
    +	@Override
    +	public void notifyOfCompletedCheckpoint(long checkpointId) throws Exception {
    +		super.notifyOfCompletedCheckpoint(checkpointId);
    +		saveHandleInState(checkpointId);
    +
    +		synchronized (state.pendingHandles) {
    +			Set<Long> pastCheckpointIds = state.pendingHandles.keySet();
    +			Set<Long> checkpointsToRemove = new HashSet<>();
    +			for (Long pastCheckpointId : pastCheckpointIds) {
    +				if (pastCheckpointId <= checkpointId) {
    +					List<StateHandle<DataInputView>> handles = state.pendingHandles.get(pastCheckpointId);
    +					for (StateHandle<DataInputView> handle : handles) {
    +						DataInputView in = handle.getState(getUserCodeClassloader());
    +						while (in.readByte() == 1) {
    +							IN value = serializer.deserialize(in);
    +							sendValue(value);
    +						}
    +						checkpointsToRemove.add(pastCheckpointId);
    +					}
    +				}
    +			}
    +			for (Long toRemove : checkpointsToRemove) {
    +				state.pendingHandles.remove(toRemove);
    +			}
    +		}
    +	}
    +
    +	/**
    +	 * Write the given element into the backend.
    +	 * @param value value to be written
    +	 * @throws Exception
    +     */
    +	protected abstract void sendValue(IN value) throws Exception;
    +
    +	@Override
    +	public void processElement(StreamRecord<IN> element) throws Exception {
    +		IN value = element.getValue();
    +		if (serializer == null) {
    +			typeInfo = TypeExtractor.getForObject(value);
    +			serializer = typeInfo.createSerializer(new ExecutionConfig());
    --- End diff --
    
    Of course you should automatically extract the `TypeInformation` and then create the corresponding
`TypeSerializer` when you create the sink. But you shouldn't pass the `TypeInformation` into
the sink and ship it to the cluster.


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