[GitHub] jsun98 commented on a change in pull request #6431: Add Kinesis Indexing Service to core Druid

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jsun98 commented on a change in pull request #6431: Add Kinesis Indexing Service to core Druid
URL: https://github.com/apache/incubator-druid/pull/6431#discussion_r230537959
 
 

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 File path: indexing-service/src/main/java/org/apache/druid/indexing/seekablestream/SeekableStreamPartitions.java
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+/*
+ * 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.druid.indexing.seekablestream;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableMap;
+
+import javax.validation.constraints.NotNull;
+import java.util.Map;
+import java.util.Objects;
+
+/**
+ * class that encapsulates a map of partitionId -> sequenceNumber.
+ * To be backward compatible with both Kafka and Kinesis datasource metadata when
+ * deserializing json. Redundant constrcturo fields stream, topic and
+ * partitionSequenceNumberMap and partitionOffsetMap are created. Only one of topic, stream
+ * should have a non-null value and only one of partitionOffsetMap and partitionSequenceNumberMap
+ * should have a non-null value.
+ * <p>
+ * Redundant getters
+ * are used for proper Jackson serialization/deserialization when processing terminologies
+ * used by Kafka and kinesis (i.e. topic vs. name)
+ *
+ * @param <partitionType> partition id type
+ * @param <sequenceType> sequence number type
+ */
+public class SeekableStreamPartitions<partitionType, sequenceType>
+{
+  public static final String NO_END_SEQUENCE_NUMBER = "NO_END_SEQUENCE_NUMBER";
+
+  // stream/topic
+  private final String name;
+  // partitionId -> sequence number
+  private final Map<partitionType, sequenceType> map;
+
+  @JsonCreator
+  public SeekableStreamPartitions(
+      @JsonProperty("stream") final String stream,
+      @JsonProperty("topic") final String topic,
+      @JsonProperty("partitionSequenceNumberMap") final Map<partitionType, sequenceType> partitionSequenceNumberMap,
+      @JsonProperty("partitionOffsetMap") final Map<partitionType, sequenceType> partitionOffsetMap
+  )
+  {
+    this.name = stream == null ? topic : stream;
+    this.map = ImmutableMap.copyOf(partitionOffsetMap == null
+                                   ? partitionSequenceNumberMap
+                                   : partitionOffsetMap);
+    Preconditions.checkArgument(this.name != null);
+    Preconditions.checkArgument(map != null);
+  }
+
+  // constructor for backward compatibility
+  public SeekableStreamPartitions(@NotNull final String id, final Map<partitionType, sequenceType> partitionOffsetMap)
+  {
+    this(id, null, partitionOffsetMap, null);
+  }
+
+  @JsonProperty
+  public String getName()
 
 Review comment:
   the reason for having redundant getters is that Jackson has problems deserializing json strings from kafka and kinesis. For example in `KinesisIOConfig`
   ```java
     @JsonCreator
     public KinesisIOConfig(
         @JsonProperty("baseSequenceName") String baseSequenceName,
         @JsonProperty("startPartitions") SeekableStreamPartitions<String, String> startPartitions,
   ```
   initializing startPartitions requires the getter `getPartitionSequenceNumberMap` while in the kafka version, the getter required is `getPartitionOffsetMap`. I haven't been able to find another workaround, perhaps we could also create a `KafkaStreamPartitions` and `KinesisStreamPartitions` class, but that would introduce 2 redundant classes.

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