Page History

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1. Add a new headers length and value (byte[]) to the core message format.
2. Create a Header Interface and implementing class

   1. Interface

      Code Block
      public interface Header { String key(); byte[] value(); }

   2. Implementation Detail

      1. Add a String key field to Header implementing class

      2. Add a byte[] value field to Header implementing class

3. Create a Headers Interface and implementing class 

   1. Interface

      Code Block
      public interface Headers extends Iterable<Header> { Headers add(String key, byte[] value); Collection<byte[]> get(String key); Set<String> keys(); }

   2. Implementation Detail

      1. Add a headers Header[] field to Headers implementation class

      2. Add accessor methods on the Headers class - void Headers add(String key, byte[] value) and a Collection<byte[]> get(String)
      3. implement Iterable<Header>
4. Add a headers field to ProducerRecord and ConsumerRecord. 
5. Add accessor methods on the Producer/ConsumerRecord Headers getHeaders()

   1. Code Block
      public class ProducerRecord<K, V> { ... public Headers getHeaders(); ... }

      Code Block
      public class ConsumerRecord<K, V> { ... public Headers getHeaders(); ... }

6. Add ProduceRequest/ProduceResponse V4 which uses the new message format.
7. Add FetchRequest/FetchResponse V4 which uses the new message format.
8. The serialisation of the [String, byte[]] header array will on the wire using a strict format
9. Each headers value will be custom serialisable by the interceptors/plugins that use the header.

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