說明

之前我們使用的是RabbitMQ與Stream的結合完成訊息驅動模組，這次使用Kafka與Stream。

目標

本文的目的在於結合Kafka與Stream來處理訊息通訊，採取自定義編寫Sink（input）和Source（output）來設定多通道訊息和消費組、消費分割槽等操作實現基本的訊息驅動的微服務架構。

快速開始

環境：伺服器端java 1.8、kafka 0.10.1.1、zookeeper 3.4.8（kafka內建）；程式設計環境java 1.8、SpringBoot 1.5.2.RELEASE、SpringCloud Dalston.SR2。更換版本後注意伺服器端kafka版本與SpringCloud使用的kafka版本一致

1 修改伺服器端kafka配置檔案

2）切換到安裝目錄，修改server.properties配置檔案：

cd /***/kafka_2.10-0.10.1.1/
vim config/server.properties

修改如下

# 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

# Switch to enable topic deletion or not, default value is false
delete.topic.enable=true

############################# 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 = security_protocol://host_name:port
#   EXAMPLE:
#     listeners = PLAINTEXT://your.host.name:9092
listeners=PLAINTEXT://0.0.0.0:9092

# 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().
# 最好像這樣使用地址對映，直接填寫ip外網可能會連線不上kafka
advertised.listeners=PLAINTEXT://YUNLINGFLY-Backup0:9092

# The number of threads handling network requests
num.network.threads=3

# The number of threads doing 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 seperated list of directories under which to store log files
log.dirs=/usr/springboottest/kafka_2.10-0.10.1.1/somelogs

# 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

############################# 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 exceessive 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
log.retention.hours=168

# A size-based retention policy for logs. Segments are pruned from the log as long as the remaining
# segments don't drop below log.retention.bytes.
#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=localhost:2181

# Timeout in ms for connecting to zookeeper
zookeeper.connection.timeout.ms=400000

# 配置的超時時間太短，Zookeeper沒有讀完Consumer的資料，連線就被Consumer斷開了！
zookeeper.session.timeout.ms=400000
 

注意事項：kafka 0.10.1.1不需要配置advertised.host.name，advertised.port引數，advertised.listeners包括上述兩項；listeners=PLAINTEXT://0.0.0.0:9092表示繫結所有網絡卡地址

3）修改hosts檔案（Windows的hosts檔案在C:\Windows\System32\drivers\etc\目錄下）：

cd ~
vim /etc/hosts

新增一行對映如下（注意填寫伺服器外網地址）：

xxx.xxx.xxx.xxx    YUNLINGFLY-Backup0

4）修改程式設計環境的hosts檔案和步驟3一樣

5）重啟伺服器reboot（Windows可以使用ipconfig/flushdns重新整理hosts配置），重新開啟Zookeeper服務，開啟kafka-server（具體命令檢視

配置到此結束。

2 編寫程式

其實使用kafka和RabbitMQ的區別是在於配置檔案的不同，所以不重複寫了，具體程式碼參照我的另一篇部落格 -> SpringCloud Stream的使用

需要改變的地方是pom.xml引入的包，將spring-cloud-starter-stream-rabbitmq改為spring-cloud-starter-stream-kafka（SpringCloud與SpringBoot版本在最開始說明了）：

		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-stream-kafka</artifactId>
		</dependency>

application.yml刪除spring.rabbit屬性，新增如下程式碼：

spring:
  cloud:
    stream:
      # 設定成使用kafka
      kafka:
        binder:
          # Kafka的服務端列表，預設localhost
          brokers: xxx.xxx.xxx.xxx:9092
          # Kafka服務端連線的ZooKeeper節點列表，預設localhost
          zkNodes: xxx.xxx.xxx.xxx:2181
          minPartitionCount: 1
          autoCreateTopics: true
          autoAddPartitions: true

執行結果

在這之前還可以看到kafka的配置引數如：

使用命令bin/kafka-topics.sh --list --zookeeper localhost:2181也可以看到我們建立的通道