Broker

A broker is the server that stores and manages messages.

Example:

Kafka Broker

Responsibilities:

• Store messages
• Handle producer writes
• Serve consumer reads

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Why Brokers Exist

Broker acts as the central event store.

Instead of services communicating directly:

Service A → Service B

We use:

Service A → Broker → Service B

Benefits:

• decoupling
• durability
• scalability

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Kafka Broker

A Kafka broker:

• stores topic partitions
• accepts producer writes
• serves consumer reads

Kafka typically runs multiple brokers forming a cluster.

Example cluster:

Broker 1
Broker 2
Broker 3

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Where Kafka Stores Data

Kafka stores data as log segment files.

Example location:

/var/lib/kafka/data/topic-name/partition-0

Example file:

00000000000000000000.log

Kafka appends messages sequentially.

Kafka is essentially a distributed commit log.

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Broker Failure Scenario

If a broker goes down:

Kafka cluster continues operating.

Example:

Topic partition replicated

Replica brokers take over.

This is called replication.

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