Package com.linkedin.venice.message

Class KafkaKey

java.lang.Object
com.linkedin.venice.message.KafkaKey
All Implemented Interfaces:
Measurable
public class KafkaKey extends Object implements Measurable
Class which stores the components of a Kafka Key, and is the format specified in the KafkaKeySerializer.

  • Field Details

    • CONTROL_MESSAGE_KAFKA_KEY_LENGTH

      public static final int CONTROL_MESSAGE_KAFKA_KEY_LENGTH
      For control messages, the Key part of the KafkaKey includes the producer GUID, segment and sequence number. N.B.: This could be optimized further by defining an Avro record to hold this data, since Avro would use variable length encoding for the two integers, which would be smaller than their regular size.

    • HEART_BEAT

      public static final KafkaKey HEART_BEAT

    • DOL_STAMP

      public static final KafkaKey DOL_STAMP
      Special key for Declaration of Leadership (DoL) control messages.

      Used during leader handover to confirm the new leader can write to and consume from the local VT. This is distinct from HEART_BEAT to clearly separate leadership declaration from heartbeat semantics.

      The DoL mechanism provides deterministic confirmation that a new leader has successfully:

      • Produced a message to the local version topic (VT)
      • Consumed that message back from VT (loopback confirmation)

      This eliminates the need for time-based waits during leader handover and provides strong guarantees that the leader is ready to switch to consuming from the leader source topic (remote VT or RT topic).

  • Constructor Details

    • KafkaKey

      public KafkaKey(@Nonnull MessageType messageType, @Nonnull byte[] key)

    • KafkaKey

      public KafkaKey(byte keyHeaderByte, @Nonnull byte[] key)

  • Method Details

    • getKeyHeaderByte

      public byte getKeyHeaderByte()
      The key header byte is the first byte in the content of the Kafka key. This is significant because it affects Kafka's Log Compaction. For MessageType.PUT and MessageType.DELETE, we want to use the exact same Kafka key, so the header byte needs to be the same. For control messages, however, we want them to be name-spaced on their own, so that they do not collide with the data when Log Compaction runs.
      Returns:
      a single byte: '0' for PUT and DELETE, or '2' for CONTROL_MESSAGE

    • isControlMessage

      public boolean isControlMessage()
      Returns:
      true if this key corresponds to a control message, and false otherwise.

    • isGlobalRtDiv

      public boolean isGlobalRtDiv()
      Returns:
      true if this key corresponds to a GlobalRtDiv message, and false otherwise.

    • getKey

      public byte[] getKey()
      Returns:
      the content of the key (everything beyond the first byte)

    • getKeyLength

      public int getKeyLength()

    • toString

      public String toString()
      Overrides:
      toString in class Object

    • getHeapSize

      public int getHeapSize()
      Specified by:
      getHeapSize in interface Measurable