Github user abhishekagarwal87 commented on a diff in the pull request:
https://github.com/apache/storm/pull/1131#discussion_r56469003
--- Diff:
external/storm-kafka-client/src/main/java/org/apache/storm/kafka/spout/KafkaRecordTupleBuilder.java
---
@@ -0,0 +1,44 @@
+/*
+ * 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
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+package org.apache.storm.kafka.spout;
+
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.storm.tuple.Fields;
+import org.apache.storm.tuple.Values;
+
+import java.util.List;
+
+public class KafkaRecordTupleBuilder<K, V> implements
KafkaSpoutTupleBuilder<K, V> {
+ @Override
+ public List<Object> buildTuple(final ConsumerRecord<K, V>
consumerRecord, KafkaSpoutStreams kafkaSpoutStreams) {
--- End diff --
There are three entities being constructed
1. Tuple - This is a list of objects being emitted by the spout e.g.
["electronics", "abhishek", "router"]
2. OutputFields - this indicates the position of fields by their name e.g.
[CATEGORY_NAME, USER_NAME, ITEM_NAME]
The bolt uses the field name in OutputFields to access the value in tuple.
e.g. one might access category using `String category =
tuple.getStringByField(CATEGORY_NAME)`
Person who is constructing the tuple, knows which positions of different
fields in tuple. That's why I suggested to have tuple building and output
fields in single interface because these two are tied and need to be consistent
with each other.
3. Schema - *a subset of the output fields* - I am not sure what it is. can
you elaborate more on this?
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