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From tzulitai <...@git.apache.org>
Subject [GitHub] flink pull request #2369: [FLINK-4035] Add a streaming connector for Apache ...
Date Sat, 20 Aug 2016 02:36:06 GMT
Github user tzulitai commented on a diff in the pull request:

    https://github.com/apache/flink/pull/2369#discussion_r75571320
  
    --- Diff: flink-streaming-connectors/flink-connector-kafka-0.10/src/main/java/org/apache/flink/streaming/connectors/kafka/FlinkKafkaProducer010.java
---
    @@ -0,0 +1,198 @@
    +/*
    + * 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.connectors.kafka;
    +
    +import org.apache.flink.api.java.typeutils.GenericTypeInfo;
    +import org.apache.flink.streaming.api.datastream.DataStream;
    +import org.apache.flink.streaming.api.datastream.DataStreamSink;
    +import org.apache.flink.streaming.api.datastream.SingleOutputStreamOperator;
    +import org.apache.flink.streaming.api.operators.StreamSink;
    +import org.apache.flink.streaming.connectors.kafka.partitioner.FixedPartitioner;
    +import org.apache.flink.streaming.connectors.kafka.partitioner.KafkaPartitioner;
    +import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
    +import org.apache.flink.streaming.util.serialization.KeyedSerializationSchema;
    +import org.apache.flink.streaming.util.serialization.KeyedSerializationSchemaWrapper;
    +import org.apache.flink.streaming.util.serialization.SerializationSchema;
    +import org.apache.kafka.clients.producer.ProducerRecord;
    +
    +import java.util.Properties;
    +
    +
    +/**
    + * Flink Sink to produce data into a Kafka topic. This producer is compatible with Kafka
0.10.x
    + *
    + * Implementation note: This Producer wraps a Flink Kafka 0.9 Producer, overriding only
    + * the "processElement" / "invoke" method.
    + */
    +public class FlinkKafkaProducer010<T> extends StreamSink<T> {
    --- End diff --
    
    Overall, I think the solution here seems a bit too "hacky" to me. Here's a few disadvantages
I see: 1) the code in `processElement()` of this class is still quite a bit duplicate of the
`invoke()` in `FlinkKafaProducerBase`. 2) with `writeToKafka()` we need to have a different
usage style for the Kafka producer in 0.10, compared to previous versions.
    
    If I'm correct, I guess its due to the fact that we don't have access to the embedded
record timestamp in the provided `next` in the usual `invoke`?
    
    I'm wondering whether or not a cleaner solution is to introduce a `serializeTimestamp(T
element)` method in the `KeyedSerializationSchema`, and we can simply use that to make `FlinkKafkaProducerBase#invoke()`
more general by replacing instantiation of `ProducerRecord`s with an abstract version-specific
method. Then, `FlinkKafkaProducer010` can simply extend `FlinkKafkaProducer09`.
    
    We'll need a migration plan though if we're going to change the serialization schema interface.
If we're going for it, might as well migrate the `KeyedDeserializationSchema` to include the
timestamp too (give `null` for 0.8, 0.9).
    Otherwise, I think the solution here is ok for a short term solution. What do you think?


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