[ 
https://issues.apache.org/jira/browse/STORM-822?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15190974#comment-15190974
 ] 

ASF GitHub Bot commented on STORM-822:
--------------------------------------

Github user bastiliu commented on a diff in the pull request:

    https://github.com/apache/storm/pull/1131#discussion_r55833857
  
    --- Diff: 
external/storm-kafka-client/src/main/java/org/apache/storm/kafka/spout/KafkaSpoutStreams.java
 ---
    @@ -0,0 +1,142 @@
    +/*
    + * 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.storm.kafka.spout;
    +
    +import org.apache.storm.spout.SpoutOutputCollector;
    +import org.apache.storm.topology.OutputFieldsDeclarer;
    +import org.apache.storm.tuple.Fields;
    +import org.apache.storm.utils.Utils;
    +
    +import java.io.Serializable;
    +import java.util.ArrayList;
    +import java.util.HashMap;
    +import java.util.List;
    +import java.util.Map;
    +
    +/**
    + * Represents the output streams associated with each topic, and provides 
a public API to
    + * declare output streams and emmit tuples, on the appropriate stream, for 
all the topics specified.
    + */
    +public class KafkaSpoutStreams implements Serializable {
    +    private final Map<String, KafkaSpoutStream> topicToStream;
    +
    +    private KafkaSpoutStreams(Builder builder) {
    +        this.topicToStream = builder.topicToStream;
    +    }
    +
    +    /**
    +     * @param topic the topic for which to get output fields
    +     * @return the output fields declared
    +     */
    +    public Fields getOutputFields(String topic) {
    +        if (topicToStream.containsKey(topic)) {
    +            return topicToStream.get(topic).getOutputFields();
    +        }
    +        throw new IllegalStateException(this.getClass().getName() + " not 
configured for topic: " + topic);
    +    }
    +
    +    /**
    +     * @param topic the topic to for which to get the stream id
    +     * @return the id of the stream to where the tuples are emitted
    +     */
    +    public String getStreamId(String topic) {
    +        if (topicToStream.containsKey(topic)) {
    +            return topicToStream.get(topic).getStreamId();
    +        }
    +        throw new IllegalStateException(this.getClass().getName() + " not 
configured for topic: " + topic);
    +    }
    +
    +    /**
    +     * @return list of topics subscribed and emitting tuples to a stream 
as configured by {@link KafkaSpoutStream}
    +     */
    +    public List<String> getTopics() {
    +        return new ArrayList<>(topicToStream.keySet());
    +    }
    +
    +    void declareOutputFields(OutputFieldsDeclarer declarer) {
    +        for (KafkaSpoutStream stream : topicToStream.values()) {
    +            declarer.declareStream(stream.getStreamId(), 
stream.getOutputFields());
    +        }
    +    }
    +
    +    void emit(SpoutOutputCollector collector, MessageId messageId) {
    +        collector.emit(getStreamId(messageId.topic()), 
messageId.getTuple(), messageId);
    --- End diff --
    
    @revans2 Actually, the values of tuple have already been stored in the 
pending map of spout. But currently, we only return the message id when ack() 
or fail(). If there is a follow up JIRA to reduce the memory pressure when 
replay, we can just add a extension interface of spout, if user implements it, 
both message id and tuple values will be returned when fail().


> As a storm developer I’d like to use the new kafka consumer API (0.8.3) to 
> reduce dependencies and use long term supported kafka apis 
> --------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: STORM-822
>                 URL: https://issues.apache.org/jira/browse/STORM-822
>             Project: Apache Storm
>          Issue Type: Story
>          Components: storm-kafka
>            Reporter: Thomas Becker
>            Assignee: Hugo Louro
>




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