Kafka Remanere.txt - 'Message Delivery Guarantees of Kafka We understand the working of producers and consumers in Kafka from the last two courses Now

Kafka Remanere.txt - 'Message Delivery Guarantees of Kafka...

This preview shows page 1 - 3 out of 10 pages.

'Message Delivery Guarantees' of KafkaWe understand the working of producers and consumers in Kafka from the last two courses. Now it is time to discuss the semantics guarantees that Kafka provides between producer and consumer.The following are the multiple possible delivery gurantees that can be provided.At most once - Messages that may be lost but never redeliveredAt least once- Messages that are never lost but may redeliveredExactly once - Messages that are delivered only onceSemantics from a Producer's PerspectiveKafka's semantics are very straightforward.When a message published in Kafka is committed, it will be lost as long as the broker is alive that replicates the partition in which the message was written.When a message is published, and a network error happens, it cannot guarantee that the error occurred before or after the message was committed.Semantics from a Producer's PerspectiveIn Kafka till version 0.11.0.0,When producer failed to receive a response that a message was committed, it willresend the message.Here at-least-once delivery semantics are provided since the message will be written to log again during resending if the original message was committed.After Kafka version 0.11.0.0,Idempotent delivery option in producer ensures that the resending of a message will not result in the duplicate entries in the message log.For enabling this, the Kafka broker assigns an ID to each producer and deduplicates the messages using a sequence number with each message sent by the producer.Using transaction-like semantics, the Kafka producer also supports the ability to send messages to multiple topic partitions.Here either all the messages will be written successfully, or none of them will be written.Semantics from a Customer's PerspectiveAll replicas have the same log with the same offsets where the consumer will control its position.The consumer position will be stored in memory.In case of consumer failure, the topic partition will be taken care by another process from the stored position.Different Options for Message ProcessingLet's see the different options for processing the messages and updating its position.at-most-once semanticsat-least-once semanticsexactly-once semanticsAt-Most-Once:Message pulled onceMay or may not be receivedNo duplicatesPossible missing dataAt-Least-Once:Message pulled once or more than once; processed every time.Receipt guaranteedLikely duplicatesNo missing data
Background image
Exactly-Once:Message pulled once or more than once; processed once.Receipt guaranteedNo DuplicatesNo Missing dataTwo-Phase CommitWhen writing a message to an external system, the problem is in need to coordinate the consumer position with what is stored as output.This can be achieved by introducing a "two-phase commit" between the storage of the consumer position and the storage of the consumer output.
Background image
Image of page 3

You've reached the end of your free preview.

Want to read all 10 pages?

  • Summer '17
  • Disk partitioning

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture