The underlying implementation principle of Kafka message queue

Overview

Kafka is a distributed, A scalable message queuing system that can handle large amounts of data with high throughput and low latency. Kafka was originally developed by LinkedIn and is now a top-level project of the Apache Software Foundation.

Architecture

Kafka is a distributed system consisting of multiple servers. Each server is called a node, and each node is an independent process. Nodes are connected through a network to form a cluster.

Data in a Kafka cluster is stored in partitions, and each partition is an ordered, immutable log file. Partition is the basic unit of Kafka data storage and the basic unit of Kafka for data replication and failover.

Data in a Kafka cluster is accessed by producers and consumers. Producers write data to the Kafka cluster, and consumers read data from the Kafka cluster.

Data Storage

Data in Kafka is stored in partitions, and each partition is an ordered, immutable log file. Partition is the basic unit of Kafka data storage and the basic unit of Kafka for data replication and failover.

Each partition has a unique ID and consists of a leader node and multiple replica nodes. The leader node is responsible for writing data to the partition, and the replica node is responsible for copying data from the leader node.

When the producer writes data to the Kafka cluster, the data will be written to the leader node. The leader node will replicate the data to the replica nodes. When a consumer reads data from the Kafka cluster, the data is read from the replica node.

Data replication

Data replication in Kafka is achieved through the copy mechanism. Each partition has a leader node and multiple replica nodes. The leader node is responsible for writing data to the partition, and the replica node is responsible for copying data from the leader node.

When the leader node fails, one of the replica nodes will become the new leader node. The new leader node will continue to write data to the partition and copy data from other replica nodes.

The data replication mechanism in Kafka can ensure the reliability and availability of data. Even if the leader node fails, data is not lost and consumers can still read data from the Kafka cluster.

Failover

Failover in Kafka is implemented through the replica mechanism. When the leader node fails, one of the replica nodes becomes the new leader node. The new leader node will continue to write data to the partition and copy data from other replica nodes.

The failover mechanism in Kafka can ensure the reliability and availability of data. Even if the leader node fails, data is not lost and consumers can still read data from the Kafka cluster.

Producer

Producers are clients that write data to the Kafka cluster. A producer can be any client that can send HTTP requests, such as a Java application, Python application, or C application.

When the producer writes data to the Kafka cluster, it needs to specify the partition to be written. Producers can choose to write data to specific partitions or write data to random partitions.

The producer can also specify the message key and message value of the data. The message key is used to uniquely identify a message, and the message value is the actual content of the message.

Consumer

Consumers are clients that read data from the Kafka cluster. A consumer can be any client that can receive HTTP requests, such as a Java application, Python application, or C application.

When consumers read data from the Kafka cluster, they need to specify the partition to read. Consumers can choose to read data from specific partitions or from all partitions.

Consumers can also specify the offset to read. The offset is used to uniquely identify a message in the partition. Consumers can choose to start reading data from a specific offset or start reading data from the latest offset.

Application scenarios

Kafka can be used in a variety of application scenarios, such as:

• Log collection: Kafka can be used to collect and store Log data from different systems.
• Data analysis: Kafka can be used to collect and store data from different systems, and then analyze the data.
• Stream processing: Kafka can be used to process data streams from different systems.
• Event-driven architecture: Kafka can be used to implement event-driven architecture.

Code Example

The following is an example of a Kafka producer written in Java:

import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.ProducerConfig;
import org.apache.kafka.clients.producer.ProducerRecord;

import java.util.Properties;

public class KafkaProducerExample {

    public static void main(String[] args) {
        // Create a Kafka producer
        Properties properties = new Properties();
        properties.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
        properties.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringSerializer");
        properties.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringSerializer");
        KafkaProducer<String, String> producer = new KafkaProducer<>(properties);

        // Create a Kafka record
        ProducerRecord<String, String> record = new ProducerRecord<>("my-topic", "hello, world");

        // Send the record to Kafka
        producer.send(record);

        // Close the producer
        producer.close();
    }
}

The following is an example written in Java Kafka consumer example:

import org.apache.kafka.clients.consumer.ConsumerConfig;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.KafkaConsumer;

import java.util.Collections;
import java.util.Properties;

public class KafkaConsumerExample {

    public static void main(String[] args) {
        // Create a Kafka consumer
        Properties properties = new Properties();
        properties.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
        properties.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
        properties.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
        properties.put(ConsumerConfig.GROUP_ID_CONFIG, "my-group");
        KafkaConsumer<String, String> consumer = new KafkaConsumer<>(properties);

        // Subscribe to a topic
        consumer.subscribe(Collections.singletonList("my-topic"));

        // Poll for new records
        while (true) {
            ConsumerRecords<String, String> records = consumer.poll(100);

            for (ConsumerRecord<String, String> record : records) {
                System.out.println(record.key() + ": " + record.value());
            }
        }

        // Close the consumer
        consumer.close();
    }
}

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