探索ClickHouse——连接Kafka和Clickhouse

安装Kafka

新增用户

sudo adduser kafka
sudo adduser kafka sudo
su -l kafka

安装JDK

sudo apt-get install openjdk-8-jre

下载解压kafka

可以从https://downloads.apache.org/kafka/下找到希望安装的版本。需要注意的是，不要下载路径包含src的包，否则会报“Classpath is empty”之类的错误。

mkdir ~/Downloads
curl "https://downloads.apache.org/kafka/3.5.1/kafka_2.13-3.5.1.tgz" -o ~/Downloads/kafka.tgz
mkdir ~/kafka && cd ~/kafka
tar -xvzf ~/Downloads/kafka.tgz --strip 1

配置

配置kafka

vim ~/kafka/config/server.properties

将下面这行加入文件的末尾

# ~/kafka/config/server.properties
delete.topic.enable=true

同时修改log的路径

# ~/kafka/config/server.properties
log.dirs=/home/kafka/logs

创建zookeeper service

sudo vim /etc/systemd/system/zookeeper.service

将下面内容填入上述文件中

[Unit]
Requires=network.target remote-fs.target
After=network.target remote-fs.target[Service]
Type=simple
User=kafka
ExecStart=/home/kafka/kafka/bin/zookeeper-server-start.sh /home/kafka/kafka/config/zookeeper.properties
ExecStop=/home/kafka/kafka/bin/zookeeper-server-stop.sh
Restart=on-abnormal[Install]
WantedBy=multi-user.target

创建kafka service

sudo vim /etc/systemd/system/kafka.service

将下面内容填入上述文件中

[Unit]
Requires=zookeeper.service
After=zookeeper.service[Service]
Type=simple
User=kafka
ExecStart=/bin/sh -c '/home/kafka/kafka/bin/kafka-server-start.sh /home/kafka/kafka/config/server.properties > /home/kafka/kafka/kafka.log 2>&1'
ExecStop=/home/kafka/kafka/bin/kafka-server-stop.sh
Restart=on-abnormal[Install]
WantedBy=multi-user.target

启动kafka#

启动服务

sudo systemctl start kafka

查看状态

sudo systemctl status kafka

● kafka.service
Loaded: loaded (/etc/systemd/system/kafka.service; enabled; vendor preset: enabled)
Active: active (running) since Thu 2023-09-28 03:09:39 UTC; 4s ago
Main PID: 3561758 (sh)
Tasks: 42 (limit: 2143)
Memory: 292.4M
CPU: 2.768s
CGroup: /system.slice/kafka.service
├─3561758 /bin/sh -c “/home/kafka/kafka/bin/kafka-server-start.sh /home/kafka/kafka/config/server.properties > /home/kafka/kafka/kafka.log 2>&1”
└─3561760 java -Xmx1G -Xms1G -server -XX:+UseG1GC -XX:MaxGCPauseMillis=20 -XX:InitiatingHeapOccupancyPercent=35 -XX:+ExplicitGCInvokesConcurrent -XX:MaxInlineLevel=15 -Djava.awt.headless=true -Xloggc:/>
Sep 28 03:09:39 ubuntua systemd[1]: Started kafka.service.

可以看到kafka已经处于running状态。

测试

创建Topic

~/kafka/bin/kafka-topics.sh --create --bootstrap-server localhost:2181 --replication-factor 1 --partitions 1 --topic TutorialTopic

发送消息

echo "Hello, World" | ~/kafka/bin/kafka-console-producer.sh --broker-list localhost:9092 --topic TutorialTopic > /dev/null

订阅Topic

新启动一个界面，执行下面命令

~/kafka/bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic TutorialTopic --from-beginning

它会收到上面发的消息

Hello, World

连接

创建表

使用kafka engine将kafka中的流映射到一个表中。我们以《探索ClickHouse——使用Projection加速查询》中的数据为例。

clickhouse-client --stream_like_engine_allow_direct_select 1

CREATE TABLE uk_price_paid_from_kafka (uuid_string String, price_string String, time String, postcode String, a String, b String, c String, addr1 String, addr2 String, street String, locality String, town String, district String, county String, d String, e String) ENGINE = Kafka SETTINGS kafka_broker_list = 'localhost:9092', kafka_topic_list='TutorialTopic', kafka_group_name='clickhouse', kafka_format='CSV', kafka_skip_broken_messages=1, kafka_num_consumers=1;

CREATE TABLE uk_price_paid_from_kafka
(
uuid_string String,
price_string String,
time String,
postcode String,
a String,
b String,
c String,
addr1 String,
addr2 String,
street String,
locality String,
town String,
district String,
county String,
d String,
e String
)
ENGINE = Kafka
SETTINGS kafka_broker_list = ‘localhost:9092’, kafka_topic_list = ‘TutorialTopic’, kafka_group_name = ‘clickhouse’, kafka_format = ‘CSV’, kafka_skip_broken_messages = 1, kafka_num_consumers = 1
Query id: 07a063e9-6a61-42c0-8fec-1fe2f119ee28
Ok.
0 rows in set. Elapsed: 0.008 sec.

给kafka发送消息

~/kafka/bin/kafka-console-producer.sh --broker-list localhost:9092 --topic TutorialTopic

进入消息输入模式，发送下面两个消息

"{F887F88E-7D15-4415-804E-52EAC2F10958}","70000","1995-07-07 00:00","MK15 9HP","D","N","F","31","","ALDRICH DRIVE","WILLEN","MILTON KEYNES","MILTON KEYNES","MILTON KEYNES","A","A"
"{40FD4DF2-5362-407C-92BC-566E2CCE89E9}","44500","1995-02-03 00:00","SR6 0AQ","T","N","F","50","","HOWICK PARK","SUNDERLAND","SUNDERLAND","SUNDERLAND","TYNE AND WEAR","A","A"

Clickhouse收到消息

在clickhouse-client交互终端中执行下面指令：

select * from uk_price_paid_from_kafka;

可以看到之前发送给kafka Topic的内容在Clickhouse中被收到了。

问题

后面我再在clickhouse-client交互终端中查询不到数据了。即使我们给kafka该主题发消息，也查询不到。后面我们再将《探索ClickHouse——使用MaterializedView存储kafka传递的数据》中讲解使用MaterializedView清洗和固化kafka的数据。

参考资料

• https://openjdk.org/install/
• https://kafka.apache.org/quickstart
• https://www.digitalocean.com/community/tutorials/how-to-install-apache-kafka-on-ubuntu-20-04#step-2-mdash-downloading-and-extracting-the-kafka-binaries
• https://cloud.tencent.com/developer/article/1892086
• https://sineyuan.github.io/post/clickhouse-kafka/