Github user gauravgopi123 commented on a diff in the pull request:
https://github.com/apache/incubator-apex-malhar/pull/156#discussion_r48898878
--- Diff:
contrib/src/main/java/com/datatorrent/contrib/kafka/KafkaTopicOffsetManager.java
---
@@ -0,0 +1,487 @@
+/**
+ * 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 com.datatorrent.contrib.kafka;
+
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.ListIterator;
+import java.util.Map;
+import java.util.Map.Entry;
+
+import kafka.api.ConsumerMetadataRequest;
+import kafka.cluster.Broker;
+import kafka.common.ErrorMapping;
+import kafka.common.OffsetAndMetadata;
+import kafka.common.OffsetMetadataAndError;
+import kafka.common.TopicAndPartition;
+import kafka.javaapi.ConsumerMetadataResponse;
+import kafka.javaapi.OffsetCommitRequest;
+import kafka.javaapi.OffsetCommitResponse;
+import kafka.javaapi.OffsetFetchRequest;
+import kafka.javaapi.OffsetFetchResponse;
+import kafka.network.BlockingChannel;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.datatorrent.contrib.kafka.KafkaPartition;
+import com.datatorrent.contrib.kafka.OffsetManager;
+
+public class KafkaTopicOffsetManager implements OffsetManager
+{
+
+ private static final Logger LOG =
LoggerFactory.getLogger(KafkaTopicOffsetManager.class);
+
+ private transient List<TopicAndPartition> partitionList;
+
+ private static final int DEFAULT_RETRY_COUNT = 3;
+
+ private String consumerGroup;
+ private String clientId;
+
+ private String hostname;
+
+ private int partitionCount;
+
+ private String topic;
+
+ private int port;
+
+ private int retry;
+
+ private long waitTimeout;
+
+ /**
+ * @return the port
+ */
+ public int getPort()
+ {
+ return port;
+ }
+
+ /**
+ * @param port
+ * the port to set
+ */
+ public void setPort(int port)
+ {
+ this.port = port;
+ }
+
+ /**
+ * @return the hostname
+ */
+ public String getHostname()
+ {
+ return hostname;
+ }
+
+ /**
+ * @param hostname
+ * the hostname to set
+ */
+ public void setHostname(String hostname)
+ {
+ this.hostname = hostname;
+ }
+
+ /**
+ * @return the partitionCount
+ */
+ public int getPartitionCount()
+ {
+ return partitionCount;
+ }
+
+ /**
+ * @param partitionCount
+ * the partitionCount to set
+ */
+ public void setPartitionCount(int partitionCount)
+ {
+ this.partitionCount = partitionCount;
+ }
+
+ /**
+ * @return the topic
+ */
+ public String getTopic()
+ {
+ return topic;
+ }
+
+ /**
+ * @param topic
+ * the topic to set
+ */
+ public void setTopic(String topic)
+ {
+ this.topic = topic;
+ }
+
+ private Map<TopicAndPartition, Long> offsetsMap;
+
+ /**
+ * @return the offsetsMap
+ */
+ public Map<TopicAndPartition, Long> getOffsetsMap()
+ {
+ return offsetsMap;
+ }
+
+ /**
+ * @param offsetsMap
+ * the offsetsMap to set
+ */
+ public void setOffsetsMap(Map<TopicAndPartition, Long> offsetsMap)
+ {
+ this.offsetsMap = offsetsMap;
+ }
+
+ private int retryCount;
+
+ /**
+ * @return the retryCount
+ */
+ public int getRetryCount()
+ {
+ return retryCount;
+ }
+
+ /**
+ * @param retryCount
+ * the retryCount to set
+ */
+ public void setRetryCount(int retryCount)
+ {
+ this.retryCount = retryCount;
+ }
+
+ private int correlationId;
+
+ /**
+ * @return the correlationId
+ */
+ public int getCorrelationId()
+ {
+ return correlationId;
+ }
+
+ /**
+ * @param correlationId
+ * the correlationId to set
+ */
+ public void setCorrelationId(int correlationId)
+ {
+ this.correlationId = correlationId;
+ }
+
+ /**
+ * @return the partitionList
+ */
+ public List<TopicAndPartition> getPartitionList()
+ {
+ return partitionList;
+ }
+
+ /**
+ * @param partitionList
+ * the partitionList to set
+ */
+ public void setPartitionList(List<TopicAndPartition> partitionList)
+ {
+ this.partitionList = partitionList;
+ }
+
+ /**
+ * @return the consumerGroup
+ */
+ public String getConsumerGroup()
+ {
+ return consumerGroup;
+ }
+
+ /**
+ * @param consumerGroup
+ * the consumerGroup to set
+ */
+ public void setConsumerGroup(String consumerGroup)
+ {
+ this.consumerGroup = consumerGroup;
+ }
+
+ /**
+ * @return the clientId
+ */
+ public String getClientId()
+ {
+ return clientId;
+ }
+
+ /**
+ * @param clientId
+ * the clientId to set
+ */
+ public void setClientId(String clientId)
+ {
+ this.clientId = clientId;
+ }
+
+ private transient BlockingChannel channel;
+
+ /**
+ * @return the channel
+ */
+ public BlockingChannel getChannel()
+ {
+ return channel;
+ }
+
+ /**
+ * @param channel
+ * the channel to set
+ */
+ public void setChannel(BlockingChannel channel)
+ {
+ this.channel = channel;
+ }
+
+ public KafkaTopicOffsetManager()
+ {
+
+ }
+
+ public KafkaTopicOffsetManager(String hostname, int port, String
consumerGroup, String clientID, String topic,
+ int partitionCount)
+ {
+
+ partitionList = new LinkedList<TopicAndPartition>();
+
+ offsetsMap = new HashMap<TopicAndPartition, Long>();
+
+ setHostname(hostname);
+ setConsumerGroup(consumerGroup);
+ setClientId(clientID);
+ setTopic(topic);
+ setPartitionCount(partitionCount);
+ setPort(port);
+ setRetryCount(retryCount);
+
+ getConnectionHandle(getRetry());
+ }
+
+ public void getConnectionHandle(int retry)
+ {
+
+ if (retry == 0) {
+ setChannel(null);
+ return;
+ }
+
+ int correlationID = 0;
+ try {
+ BlockingChannel channel = new BlockingChannel(getHostname(),
getPort(), BlockingChannel.UseDefaultBufferSize(),
+ BlockingChannel.UseDefaultBufferSize(), (int)getWaitTimeout() *
10);
+ channel.connect();
+
+ //TODO - do a get until you get no further data from the zk/topic
+
+ for (int i = 0; i < getPartitionCount(); i++) {
+ final TopicAndPartition tempPartition = new
TopicAndPartition(getTopic(), i);
+ partitionList.add(tempPartition);
+
+ }
+
+ channel.send(new ConsumerMetadataRequest(consumerGroup, (short)1,
correlationID++, getClientId()));
+ ConsumerMetadataResponse metadataResponse =
ConsumerMetadataResponse.readFrom(channel.receive().buffer());
+
+ // Set the incremental correlation ID
+ setCorrelationId(correlationID);
+
+ if (metadataResponse.errorCode() == ErrorMapping.NoError()) {
+ Broker offsetManager = metadataResponse.coordinator();
+ // if the coordinator is different, from the above channel's
+ // host then reconnect
+ channel.disconnect();
+ channel = new BlockingChannel(offsetManager.host(),
offsetManager.port(),
+ BlockingChannel.UseDefaultBufferSize(),
BlockingChannel.UseDefaultBufferSize(), (int)getWaitTimeout() * 10);
+
+ channel.connect();
+ setChannel(channel);
+ LOG.info("Channel initialized");
+
+ } else {
+ setRetry(getRetry() - 1);
+ getConnectionHandle(getRetry());
+ }
+ } catch (Exception e) {
+ LOG.error("Not able to initialize the channel");
+ }
+
+ }
+
+ /**
+ * @return the retry
+ */
+ public int getRetry()
+ {
+ return retry;
+ }
+
+ /**
+ * @param retry
+ * the retry to set
+ */
+ public void setRetry(int retry)
+ {
+ this.retry = retry;
+ }
+
+ /**
+ * @return the waitTimeout
+ */
+ public long getWaitTimeout()
+ {
+ return waitTimeout;
+ }
+
+ /**
+ * @param waitTimeout
+ * the waitTimeout to set
+ */
+ public void setWaitTimeout(long waitTimeout)
+ {
+ this.waitTimeout = waitTimeout;
+ }
+
+ public void fetchOffsets()
+ {
+ // version 1 and above fetch from Kafka, version 0 fetches from
+ // ZooKeeper
+
+ OffsetFetchRequest fetchRequest = new
OffsetFetchRequest(getConsumerGroup(), getPartitionList(), (short)1,
+ getCorrelationId(), getClientId());
+ try {
+ getChannel().send(fetchRequest.underlying());
+ OffsetFetchResponse fetchResponse =
OffsetFetchResponse.readFrom(getChannel().receive().buffer());
+
+ ListIterator<TopicAndPartition> itr =
getPartitionList().listIterator();
+
+ //TODO - check and handle more error codes
+
+ while (itr.hasNext()) {
+
+ TopicAndPartition topicAndPartition = itr.next();
+ OffsetMetadataAndError result =
fetchResponse.offsets().get(topicAndPartition);
+ short offsetFetchErrorCode = result.error();
+ if (offsetFetchErrorCode ==
ErrorMapping.NotCoordinatorForConsumerCode()) {
+ getChannel().disconnect();
+
+ } else if (offsetFetchErrorCode ==
ErrorMapping.BrokerNotAvailableCode()) {
+
+ for (int i = 0; i < getRetryCount(); i++) {
+ // TODO- externalize this wait
+ getChannel().wait(getWaitTimeout());
+ result = fetchResponse.offsets().get(topicAndPartition);
+ // Exit if there is no error
+ if (result.error() == ErrorMapping.NoError()) {
+ break;
+ }
+ }
+ // retry the offset fetch (after backoff)
+ } else {
+ long retrievedOffset = result.offset();
+ // TODO- use the metadata associated with an offset, its not
required for offset maintenance as such
+ String retrievedMetadata = result.metadata();
+ getOffsetsMap().put(topicAndPartition, retrievedOffset);
+ }
+
+ }
+
+ } catch (InterruptedException e) {
+ LOG.error("Could not fetch offsets,Exception occurred" +
e.getMessage() + "Closing channel");
+ channel.disconnect();
+ }
+
+ }
+
+ @Override
+ public void updateOffsets(Map<KafkaPartition, Long> offsetsOfPartitions)
+ {
+
+ long now = System.currentTimeMillis();
+
+ Map<TopicAndPartition, OffsetAndMetadata> offsets = new
LinkedHashMap<TopicAndPartition, OffsetAndMetadata>();
+
+ // Iterate over the updated offsets from the platform's partitions and
+ // create the
+ for (Entry<KafkaPartition, Long> entry :
offsetsOfPartitions.entrySet()) {
+ KafkaPartition key = entry.getKey();
+ long value = entry.getValue();
+ offsets.put(new TopicAndPartition(key.getTopic(),
key.getPartitionId()), new OffsetAndMetadata(value, "MD", now));
--- End diff --
use entry.getValue() directly instead of declaring local `value` variable
as it is used only at one place
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