Github user harshach commented on a diff in the pull request:
https://github.com/apache/storm/pull/1131#discussion_r55942709
--- 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 --
@abhishekagarwal87 Yes with new consumer api this is limited by
max.partition.fetch.bytes , so the max will be no.of partitions x
max.partition.fetch.bytes. Given that we ask users to set the parallelism of
kafkaSpout to that of no.of partitions in a topic. So at max it will be
partitions * max.partition.fetch.bytes in a single instance of kafka spout and
in avg it wll max.partition.fetch.bytes per instance of kafka spout ( if users
configures parallelism == topic.partitions)
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