Kafka Intro With Simple Java Producer Consumers

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Cassandra / Kafka Support in EC2/AWS. Kafka Training, Kafka
Consulting
Cassandra and Kafka Support on AWS/EC2
Cloudurable
Kafka Introduction
Support around Cassandra
and Kafka running in EC2

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Cassandra / Kafka Support in EC2/AWS
Kafka Introduction Kafka messaging

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What is Kafka?
❖ Distributed Streaming Platform
❖ Publish and Subscribe to streams of records
❖ Fault tolerant storage
❖ Process records as they occur

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Kafka Usage
❖ Build real-time streaming data pipe-lines
❖ Enable in-memory microservices (actors, Akka, Vert.x,
Qbit)
❖ Build real-time streaming applications that react to
streams
❖ Real-time data analytics
❖ Transform, react, aggregate, join real-time data flows

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Kafka Use Cases
❖ Metrics / KPIs gathering
❖ Aggregate statistics from many sources
❖ Even Sourcing
❖ Used with microservices (in-memory) and actor systems
❖ Commit Log
❖ External commit log for distributed systems. Replicated
data between nodes, re-sync for nodes to restore state
❖ Real-time data analytics, Stream Processing, Log
Aggregation, Messaging, Click-stream tracking, Audit trail,
etc.

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Who uses Kafka?
❖ LinkedIn: Activity data and operational metrics
❖ Twitter: Uses it as part of Storm – stream processing
infrastructure
❖ Square: Kafka as bus to move all system events to various
Square data centers (logs, custom events, metrics, an so
on). Outputs to Splunk, Graphite, Esper-like alerting
systems
❖ Spotify, Uber, Tumbler, Goldman Sachs, PayPal, Box,
Cisco, CloudFlare, DataDog, LucidWorks, MailChimp,
NetFlix, etc.

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Kafka Fundamentals
❖ Records have a key, value and timestamp
❖ Topic a stream of records
❖ Log topic storage on disk
❖ Partition / Segments (parts of Topic Log)
❖ Producer API to produce a streams or records
❖ Consumer API to consume a stream of records
❖ Broker: Cluster of Kafka servers running in cluster form broker. Consists on many
processes on many servers
❖ ZooKeeper: Does coordination of broker and consumers. Consistent file system
for configuration information and leadership election

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Kafka: Topics, Producers, and
Consumers
Kafka
Cluster
Topic
Producer
Producer
Producer
Consumer
Consumer
Consumer
record
record

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ZooKeeper does coordination for Kafka Consumer
and Kafka Cluster
Kafka BrokerProducer
Producer
Producer
Consumer
Consumer
Consumer
Kafka Broker
Kafka Broker
Topic
ZooKeeper

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Kafka Extensions
❖ Streams API to transform, aggregate, process records
from a stream and produce derivative streams
❖ Connector API reusable producers and consumers
(e.g., stream of changes from DynamoDB)

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Kafka Connectors and
Streams
Kafka
Cluster
App
App
App
App
App
App
DB DB
App App
Connectors
Producers
Consumers
Streams

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Kafka Polyglot clients / Wire
protocol
❖ Kafka communication from clients and servers wire
protocol over TCP protocol
❖ Protocol versioned
❖ Maintains backwards compatibility
❖ Many languages supported

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Topics and Logs
❖ Topic is a stream of records
❖ Topics stored in log
❖ Log broken up into partitions and segments
❖ Topics is a category or stream name
❖ Topics are pub/sub
❖ Can have zero or many consumers (subscribers)
❖ Topics are broken up into partitions for speed and size

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Topic Partitions
❖ Topics are broken up into partitions
❖ Partitions are decided usually by key of record
❖ Key of record determines which partition
❖ Partitions are used to scale Kafka across many servers
❖ Record sent to correct partition by key
❖ Partitions are used to facilitate parallel consumers
❖ Records are consumed in parallel up to the number of
partitions

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Partition Log
❖ Partition is ordered, immutable sequence of records that is continually
appended to—a structured commit log
❖ Records in partitions are assigned sequential id number called
the offset
❖ Offset identifies each record within the partition
❖ Topic Partitions allow Kafka log to scale beyond a size that will fit on a
single server
❖ Topic partition must fit on servers that host it, but topic can span
many partitions hosted by many servers
❖ Topic Partitions are unit of parallelism - each consumer in a consumer
group can work on one partition at a time

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Kafka Topic Partitions Layout
0 1 42 3 5 6 7 8 9 10 11
0 1 42 3 5 6 7 8
0 1 42 3 5 6 7 8 9 10
Older Newer
0 1 42 3 5 6 7
Partition
0
Partition
1
Partition
2
Partition
3
Writes

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Kafka Record retention
❖ Kafka cluster retains all published records
❖ Time based – configurable retention period
❖ Size based
❖ Compaction
❖ Retention policy of three days or two weeks or a month
❖ It is available for consumption until discarded by time, size or
compaction
❖ Consumption speed not impacted by size

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Kafka Consumers / Producers
0 1 42 3 5 6 7 8 9 10 11
Partition
0
Consumer Group A
Producers
Consumer Group B
Consumers remember offset where they left off.
Consumers groups each have their own offset.

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Kafka Partition Distribution
❖ Each partition has leader server and zero or more follower
servers
❖ Leader handles all read and write requests for partition
❖ Followers replicate leader, and take over if leader dies
❖ Used for parallel consumer handling within a group
❖ Partitions of log are distributed over the servers in the Kafka cluster
with each server handling data and requests for a share of partitions
❖ Each partition can be replicated across a configurable number of
Kafka servers
❖ Used for fault tolerance

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Kafka Producers
❖ Producers send records to topics
❖ Producer picks which partition to send record to per
topic
❖ Can be done in a round-robin
❖ Can be based on priority
❖ Typically based on key of record
❖ Important: Producer picks partition

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Kafka Consumers
❖ Consumers are grouped into a Consumer Group
❖ Consumer group has a unique name
❖ Each consumer group is a subscriber
❖ Each consumer group maintains its own offset
❖ Multiple subscribers = multiple consumer groups
❖ A Record is delivered to one Consumer in a Consumer Group
❖ Each consumer in consumer groups takes records and only one
consumer in group gets same record
❖ Consumers in Consumer Group load balance record
consumption

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2 server Kafka cluster hosting 4 partitions (P0-P5)
Kafka Cluster
Server 2
P0 P1 P5
Server 1
P2 P3 P4
Consumer Group A
C0 C1 C3
Consumer Group B
C0 C1 C3

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Kafka Consumer
Consumption
❖ Kafka Consumer consumption divides partitions over consumer instances
❖ Each Consumer is exclusive consumer of a "fair share" of partitions
❖ Consumer membership in group is handled by the Kafka protocol
dynamically
❖ If new Consumers join Consumer group they get share of partitions
❖ If Consumer dies, its partitions are split among remaining live
Consumers in group
❖ Order is only guaranteed within a single partition
❖ Since records are typically stored by key into a partition then order per
partition is sufficient for most use cases

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Kafka vs JMS Messaging
❖ It is a bit like both Queues and Topics in JMS
❖ Kafka is a queue system per consumer in consumer group so load
balancing like JMS queue
❖ Kafka is a topic/pub/sub by offering Consumer Groups which act like
subscriptions
❖ Broadcast to multiple consumer groups
❖ By design Kafka is better suited for scale due to partition topic log
❖ Also by moving location in log to client/consumer side of equation
instead of the broker, less tracking required by Broker
❖ Handles parallel consumers better

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Kafka scalable message
storage
❖ Kafka acts as a good storage system for records/messages
❖ Records written to Kafka topics are persisted to disk and replicated to
other servers for fault-tolerance
❖ Kafka Producers can wait on acknowledgement
❖ Write not complete until fully replicated
❖ Kafka disk structures scales well
❖ Writing in large streaming batches is fast
❖ Clients/Consumers control read position (offset)
❖ Kafka acts like high-speed file system for commit log storage,
replication

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Kafka Stream Processing
❖ Kafka for Stream Processing
❖ Kafka enable real-time processing of streams.
❖ Kafka supports stream processor
❖ Stream processor takes continual streams of records from input topics, performs some
processing, transformation, aggregation on input, and produces one or more output
streams
❖ A video player app might take in input streams of videos watched and videos paused, and
output a stream of user preferences and gear new video recommendations based on recent
user activity or aggregate activity of many users to see what new videos are hot
❖ Kafka Stream API solves hard problems with out of order records, aggregating across
multiple streams, joining data from multiple streams, allowing for stateful computations, and
more
❖ Stream API builds on core Kafka primitives and has a life of its own

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Using Kafka Single
Node

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Run Kafka
❖ Run ZooKeeper
❖ Run Kafka Server/Broker
❖ Create Kafka Topic
❖ Run producer
❖ Run consumer

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Run ZooKeeper

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Run Kafka Server

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Create Kafka Topic

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Kafka Producer

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Kafka Consumer

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Running Kafka Producer and
Consumer

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Use Kafka to send and receive messages
Lab 1-A Use Kafka Use single server version of
Kafka

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Using Kafka Cluster

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Running many nodes
❖ Modify properties files
❖ Change port
❖ Change Kafka log location
❖ Start up many Kafka server instances
❖ Create Replicated Topic

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Leave everything from before
running

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Create two new
server.properties files
❖ Copy existing server.properties to server-
1.properties, server-2.properties
❖ Change server-1.properties to use port 9093, broker
id 1, and log.dirs “/tmp/kafka-logs-1”
❖ Change server-2.properties to use port 9094, broker
id 2, and log.dirs “/tmp/kafka-logs-2”

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server-x.properties

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Start second and third servers

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Create Kafka replicated topic my-
failsafe-topic

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Start Kafka consumer and
producer

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Kafka consumer and producer
running

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Use Kafka Describe Topic
The leader is broker 0
There is only one partition
There are three in-sync replicas (ISR)

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Test Failover by killing 1st
server
Use Kafka topic describe to see that a new leader was elected!
NEW LEADER IS 2!

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Use Kafka to send and receive messages
Lab 2-A Use Kafka Use a Kafka Cluster to
replicate a Kafka topic log

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Kafka Consumer
and
Producers
Working with producers and
consumers
Step by step first example

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Objectives Create Producer and Consumer
example
❖ Create simple example that creates a Kafka Consumer
and a Kafka Producer
❖ Create a new replicated Kafka topic
❖ Create Producer that uses topic to send records
❖ Send records with Kafka Producer
❖ Create Consumer that uses topic to receive messages
❖ Process messages from Kafka with Consumer

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Create Replicated Kafka
Topic

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Build script

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Create Kafka Producer to send
records
❖ Specify bootstrap servers
❖ Specify client.id
❖ Specify Record Key serializer
❖ Specify Record Value serializer

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Common Kafka imports and
constants

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Create Kafka Producer to send
records

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Send async records with Kafka
Producer

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Send sync records with Kafka
Producer

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Create Consumer using Topic to Receive
Records
❖ Specify bootstrap servers
❖ Specify client.id
❖ Specify Record Key deserializer
❖ Specify Record Value deserializer
❖ Specify Consumer Group
❖ Subscribe to Topic

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Create Consumer using Topic to Receive
Records

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Process messages from Kafka with
Consumer

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Running both Consumer and
Producer

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Java Kafka simple example
recap
❖ Created simple example that creates a Kafka
Consumer and a Kafka Producer
❖ Created a new replicated Kafka topic
❖ Created Producer that uses topic to send records
❖ Send records with Kafka Producer
❖ Created Consumer that uses topic to receive
messages
❖ Processed records from Kafka with Consumer

Kafka Intro With Simple Java Producer Consumers

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