Kafka笔记

Kafka笔记

一、引言

二、Kafka安装

2.1 下载

官网地址:http://kafka.apache.org

下载地址:http://kafka.apache.org/downloads

三、Kafka启动

3.1 启动顺序

Kafka启动需要Zookeeper环境

启动Zookeeper—> 启动Kafka

3.2 配置文件修改

3.2.1 Zookeeper配置文件

位于config/目录下的zookeeper.properties文件

#示例代码
# limitations under the License.
# the directory where the snapshot is stored.
dataDir=/tmp/zookeeper
# the port at which the clients will connect
clientPort=2181
# disable the per-ip limit on the number of connections since this is a non-production config
maxClientCnxns=0
# Disable the adminserver by default to avoid port conflicts.
# Set the port to something non-conflicting if choosing to enable this
admin.enableServer=false
# admin.serverPort=8080
3.2.2 Kafka Server配置文件

位于config/目录下的server.properties

#示例代码
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements.  See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License.  You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# see kafka.server.KafkaConfig for additional details and defaults

############################# Server Basics #############################

# The id of the broker. This must be set to a unique integer for each broker.
broker.id=0

############################# Socket Server Settings #############################

# The address the socket server listens on. It will get the value returned from 
# java.net.InetAddress.getCanonicalHostName() if not configured.
#   FORMAT:
#     listeners = listener_name://host_name:port
#   EXAMPLE:
#     listeners = PLAINTEXT://your.host.name:9092
listeners=PLAINTEXT://<阿里云内网地址>:10888
advertised.listeners=PLAINTEXT://<阿里云外网地址>:10888

# Hostname and port the broker will advertise to producers and consumers. If not set, 
# it uses the value for "listeners" if configured.  Otherwise, it will use the value
# returned from java.net.InetAddress.getCanonicalHostName().
#advertised.listeners=PLAINTEXT://your.host.name:9092

# Maps listener names to security protocols, the default is for them to be the same. See the config documentation for more details
#listener.security.protocol.map=PLAINTEXT:PLAINTEXT,SSL:SSL,SASL_PLAINTEXT:SASL_PLAINTEXT,SASL_SSL:SASL_SSL

# The number of threads that the server uses for receiving requests from the network and sending responses to the network
num.network.threads=3

# The number of threads that the server uses for processing requests, which may include disk I/O
num.io.threads=8

# The send buffer (SO_SNDBUF) used by the socket server
socket.send.buffer.bytes=102400

# The receive buffer (SO_RCVBUF) used by the socket server
socket.receive.buffer.bytes=102400

# The maximum size of a request that the socket server will accept (protection against OOM)
socket.request.max.bytes=104857600


############################# Log Basics #############################

# A comma separated list of directories under which to store log files
log.dirs=/tmp/kafka-logs

# The default number of log partitions per topic. More partitions allow greater
# parallelism for consumption, but this will also result in more files across
# the brokers.
num.partitions=1

# The number of threads per data directory to be used for log recovery at startup and flushing at shutdown.
# This value is recommended to be increased for installations with data dirs located in RAID array.
num.recovery.threads.per.data.dir=1

############################# Internal Topic Settings  #############################
# The replication factor for the group metadata internal topics "__consumer_offsets" and "__transaction_state"
# For anything other than development testing, a value greater than 1 is recommended to ensure availability such as 3.
offsets.topic.replication.factor=1
transaction.state.log.replication.factor=1
transaction.state.log.min.isr=1

############################# Log Flush Policy #############################

# Messages are immediately written to the filesystem but by default we only fsync() to sync
# the OS cache lazily. The following configurations control the flush of data to disk.
# There are a few important trade-offs here:
#    1. Durability: Unflushed data may be lost if you are not using replication.
#    2. Latency: Very large flush intervals may lead to latency spikes when the flush does occur as there will be a lot of data to flush.
#    3. Throughput: The flush is generally the most expensive operation, and a small flush interval may lead to excessive seeks.
# The settings below allow one to configure the flush policy to flush data after a period of time or
# every N messages (or both). This can be done globally and overridden on a per-topic basis.

# The number of messages to accept before forcing a flush of data to disk
#log.flush.interval.messages=10000

# The maximum amount of time a message can sit in a log before we force a flush
#log.flush.interval.ms=1000

############################# Log Retention Policy #############################

# The following configurations control the disposal of log segments. The policy can
# be set to delete segments after a period of time, or after a given size has accumulated.
# A segment will be deleted whenever *either* of these criteria are met. Deletion always happens
# from the end of the log.

# The minimum age of a log file to be eligible for deletion due to age
log.retention.hours=168

# A size-based retention policy for logs. Segments are pruned from the log unless the remaining
# segments drop below log.retention.bytes. Functions independently of log.retention.hours.
#log.retention.bytes=1073741824

# The maximum size of a log segment file. When this size is reached a new log segment will be created.
log.segment.bytes=1073741824

# The interval at which log segments are checked to see if they can be deleted according
# to the retention policies
log.retention.check.interval.ms=300000

############################# Zookeeper #############################

# Zookeeper connection string (see zookeeper docs for details).
# This is a comma separated host:port pairs, each corresponding to a zk
# server. e.g. "127.0.0.1:3000,127.0.0.1:3001,127.0.0.1:3002".
# You can also append an optional chroot string to the urls to specify the
# root directory for all kafka znodes.
zookeeper.connect=118.190.156.52:2181

# Timeout in ms for connecting to zookeeper
zookeeper.connection.timeout.ms=18000


############################# Group Coordinator Settings #############################

# The following configuration specifies the time, in milliseconds, that the GroupCoordinator will delay the initial consumer rebalance.
# The rebalance will be further delayed by the value of group.initial.rebalance.delay.ms as new members join the group, up to a maximum of max.poll.interval.ms.
# The default value for this is 3 seconds.
# We override this to 0 here as it makes for a better out-of-the-box experience for development and testing.
# However, in production environments the default value of 3 seconds is more suitable as this will help to avoid unnecessary, and potentially expensive, rebalances during application startup.
group.initial.rebalance.delay.ms=0

################################# Auto Create Topic #######################
auto.create.topics.enable=true

log.cleaner.enable=true
host.name=172.31.201.154

注意:在阿里云ECS环境中需要做地址映射,对应配置如下

#示例代码
listeners=PLAINTEXT:// 内网的ip地址:端口
advertised.listeners=PLAINTEXT://外网的ip的地址:端口
advertised.host.name= 内网的ip地址
zookeeper.connect=外网的IP地址和2181端口

3.3 启动指令

3.3.1 启动Kafka内置的Zookeeper

在Kafka安装目录下执行以下命令:

# bin/zookeeper-server-start.sh config/zookeeper.properties 
3.3.2 启动Kafka

在Kafka安装目录下执行以下命令:

#  bin/kafka-server-start.sh config/server.properties

3.4 Kafka集群启动

TODO

四、Kafka使用

QuickStart地址:http://kafka.apache.org/quickstart

五、TODO

### 尚硅谷 Kafka 学习笔记 #### 创建 Kafka 生产者并发送消息 为了创建一个简单的 Kafka 生产者并向指定主题发送消息,在命令行工具中可以执行如下操作。通过 `bin/kafka-console-producer.sh` 脚本启动生产者客户端,并指定了引导服务器地址以及目标主题名称[^1]。 ```bash [atguigu@hadoop102 kafka]$ bin/kafka-console-producer.sh --bootstrap-server hadoop102:9092 --topic first > hello ``` 此命令允许用户手动输入要发布的消息内容,每条新消息以回车键结束提交给集群处理。 #### 修改消费者配置文件设置分组ID 对于希望自定义消费逻辑的应用程序来说,调整消费者的配置参数是非常重要的一步。具体而言,可以通过编辑 `/opt/module/kafka/config/consumer.properties` 文件内的 `group.id` 属性来设定唯一的消费者组标识符[^4]。 ```properties [atguigu@hadoop103 config]$ vi consumer.properties group.id=atguigu ``` 这里展示了如何更改默认值为特定字符串(如 "atguigu"),从而确保不同实例之间不会相互干扰。 #### 实现自定义分区器 当业务需求涉及到更复杂的路由策略时,则可能需要用到自定义的 Partitioner 类型。下面给出了一种基于关键字匹配决定消息所属分区的方法示例代码片段[^5]: ```java public class MyPartitioner implements Partitioner { @Override public int partition(String topic, Object key, byte[] keyBytes, Object value, byte[] valueBytes, Cluster cluster) { String inputValue = (value != null && !"".equals(value)) ? value.toString() : ""; if ("hello".contains(inputValue)){ return 1; } else{ return 0; } } @Override public void close(){} @Override public void configure(Map<String, ?> configs){} } ``` 这段 Java 程序实现了 `Partitioner` 接口,并覆盖了其抽象方法 `partition()` 来判断传入的消息体是否包含预设关键词 `"hello"`;如果条件成立则返回整数 `1` 表明该记录应分配至编号为 `1` 的物理分区上,反之亦然。 #### 关于日志与数据存储机制的理解 值得注意的是,Kafka 中的日志目录实际上是指向实际保存二进制编码后的消息集合的位置。由于这些对象经过序列化过程变得难以直观理解,因此建议开发者熟悉相关概念以便更好地管理和维护系统性能[^2]。 另外,关于偏移量 Offset 的管理方式也值得深入探讨。每个存储单元都会依据首次出现位置获得独一无二的名字格式——即形似 `xxxxxx.kafka` 这样的文件名模式,其中 x 可能代表任意长度但始终递增的一串数字字符[^3]。
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