kafka_2.11 简单使用
进过上一篇的引导，相信大家应该都已经安装好了。这次我们就来简单使用一下。
1 创建 topic
像官网上写的那样，我们可以使用 kafka.topics.sh 脚本来创建一个 topic 。不过，前提是我们需要启动zookeeper 和 kafka 服务。
那我们就用官网上例子好了：
[root@master config]# kafka-topics.sh --create --zookeeper localhost:2181 --topic first
Missing required argument "[partitions]"
Option Description
------ -----------
--alter Alter the number of partitions,
replica assignment, and/or
configuration for the topic.
--config A topic configuration override for the
topic being created or altered.The
following is a list of valid
configurations:
cleanup.policy
compression.type
delete.retention.ms
file.delete.delay.ms
flush.messages
flush.ms
follower.replication.throttled.
replicas
index.interval.bytes
leader.replication.throttled.replicas
max.message.bytes
message.format.version
message.timestamp.difference.max.ms
message.timestamp.type
min.cleanable.dirty.ratio
min.compaction.lag.ms
min.insync.replicas
preallocate
retention.bytes
retention.ms
segment.bytes
segment.index.bytes
segment.jitter.ms
segment.ms
unclean.leader.election.enable
See the Kafka documentation for full
details on the topic configs.
--create Create a new topic.
--delete Delete a topic
--delete-config A topic configuration override to be
removed for an existing topic (see
the list of configurations under the
--config option).
--describe List details for the given topics.
--disable-rack-aware Disable rack aware replica assignment
--force Suppress console prompts
--help Print usage information.
--if-exists if set when altering or deleting
topics, the action will only execute
if the topic exists
--if-not-exists if set when creating topics, the
action will only execute if the
topic does not already exist
--list List all available topics.
--partitions <Integer: # of partitions> The number of partitions for the topic
being created or altered (WARNING:
If partitions are increased for a
topic that has a key, the partition
logic or ordering of the messages
will be affected
--replica-assignment A list of manual partition-to-broker
for the topic being
broker_id_for_part1_replica2 , created or altered.
broker_id_for_part2_replica1 :
broker_id_for_part2_replica2 , ...>
--replication-factor <Integer: The replication factor for each
replication factor> partition in the topic being created.
--topic The topic to be create, alter or
describe. Can also accept a regular
expression except for --create option
--topics-with-overrides if set when describing topics, only
show topics that have overridden
configs
--unavailable-partitions if set when describing topics, only
show partitions whose leader is not
available
--under-replicated-partitions if set when describing topics, only
show under replicated partitions
--zookeeper REQUIRED: The connection string for
the zookeeper connection in the form
host:port. Multiple URLS can be
given to allow fail-over.
[root@master config]# kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 1 --partitions 1 --topic first
Created topic "first".
[root@master config]# 哈哈，打错一次他就会给你提示，然后你知道这些参数都是什么意思了，我就不赘述了。
这样我们就创建了一个 topic ，我们还可以使用 kafka.topics.sh 这个脚本来查看 topic 的信息：
[root@master config]# kafka-topics.sh --list --zookeeper localhost:2181
first
[root@master config]# kafka-topics.sh --describe --zookeeper localhost:2181 --topic first
Topic:first PartitionCount:1 ReplicationFactor:1 Configs:
Topic: first Partition: 0 Leader: 1 Replicas: 1 Isr: 1
[root@master config]# 这里显示出来的 0、1指的是我们 kafka 中 broker 的 ID
2 创建 producer
照葫芦画瓢：
[root@master config]# kafka-console-producer.sh
Read data from standard input and publish it to Kafka.
Option Description
------ -----------
--batch-size <Integer: size> Number of messages to send in a single
batch if they are not being sent
synchronously. (default: 200)
--broker-list REQUIRED: The broker list string in
the form HOST1:PORT1,HOST2:PORT2.
--compression-codec [compression-codec] The compression codec: either 'none',
'gzip', 'snappy', or 'lz4'.If
specified without value, then it
defaults to 'gzip'
--key-serializer The class name of the message encoder
implementation to use for
serializing keys. (default: kafka.
serializer.DefaultEncoder)
--line-reader The class name of the class to use for
reading lines from standard in. By
default each line is read as a
separate message. (default: kafka.
tools.
ConsoleProducer$LineMessageReader)
--max-block-ms <Long: max block on The max time that the producer will
send> block for during a send request
(default: 60000)
--max-memory-bytes <Long: total memory The total memory used by the producer
in bytes> to buffer records waiting to be sent
to the server. (default: 33554432)
--max-partition-memory-bytes <Long: The buffer size allocated for a
memory in bytes per partition> partition. When records are received
which are smaller than this size the
producer will attempt to
optimistically group them together
until this size is reached.
(default: 16384)
--message-send-max-retries <Integer> Brokers can fail receiving the message
for multiple reasons, and being
unavailable transiently is just one
of them. This property specifies the
number of retires before the
producer give up and drop this
message. (default: 3)
--metadata-expiry-ms <Long: metadata The period of time in milliseconds
expiration interval> after which we force a refresh of
metadata even if we haven't seen any
leadership changes. (default: 300000)
--old-producer Use the old producer implementation.
--producer-property A mechanism to pass user-defined
properties in the form key=value to
the producer.
--producer.config Producer config properties file. Note
that [producer-property] takes
precedence over this config.
--property A mechanism to pass user-defined
properties in the form key=value to
the message reader. This allows
custom configuration for a user-
defined message reader.
--queue-enqueuetimeout-ms <Integer: Timeout for event enqueue (default:
queue enqueuetimeout ms> 2147483647)
--queue-size <Integer: queue_size> If set and the producer is running in
asynchronous mode, this gives the
maximum amount of messages will
queue awaiting sufficient batch
size. (default: 10000)
--request-required-acks of the producer
required acks> requests (default: 1)
--request-timeout-ms <Integer: request The ack timeout of the producer
timeout ms> requests. Value must be non-negative
and non-zero (default: 1500)
--retry-backoff-ms <Integer> Before each retry, the producer
refreshes the metadata of relevant
topics. Since leader election takes
a bit of time, this property
specifies the amount of time that
the producer waits before refreshing
the metadata. (default: 100)
--socket-buffer-size <Integer: size> The size of the tcp RECV size.
(default: 102400)
--sync If set message send requests to the
brokers are synchronously, one at a
time as they arrive.
--timeout <Integer: timeout_ms> If set and the producer is running in
asynchronous mode, this gives the
maximum amount of time a message
will queue awaiting sufficient batch
size. The value is given in ms.
(default: 1000)
--topic REQUIRED: The topic id to produce
messages to.
--value-serializer The class name of the message encoder
implementation to use for
serializing values. (default: kafka.
serializer.DefaultEncoder)
[root@master config]# kafka-console-producer.sh --broker-list localhost:9092 --topic first
this is a test.
先报错，再看参数什么含义，还是那样，不做赘述。
当命令参数正确执行之后，是没有什么反馈的，它会等待你输入”消息“，然后它会发布给 kafka，交由 kafka 保管，等待消费者进行消费。我们可以使用”Ctrl + C“来停止。
这里我输入了一句话”this is a test.“，这是我们要发布的。
3 创建 consumer
这时候我们会注意到一句话，”If you have each of the above commands running in a different terminal then you should now be able to type messages into the producer terminal and see them appear in the consumer terminal.“ 也就是说，我们如果是在两个终端上创建 producer 和 consumer 的话，我们在 producer 上输入”消息“，我们的 consumer 上会显示出来。我们来试试，重新启动一个终端用来创建 consumer 。
就像图片上显示的那样，我启动了两个。生产者一边生产，消费者一边消费…
你可能会困惑，为什么会显示两个 “Hello World !”，那是因为我为了能截上这张图，搞错了一次，producer 这边是发送了”消息“出去，我的 consumer 也再等待接收，但是它俩不是同一个 topic 。当我把 producer 和 consumer 都停掉之后重新进来就成这样了。
接下来我们使用 API 来写一下，对于安装包里的文档也是够了，打开之后特别的乱，还是看在线的文档吧。
4 API 操作
在这之前，由于我是使用 maven 来构建项目的，我们可以很方便的引入依赖的 jar 包。
新建一个 maven 项目，然后再 pom.xml 中加入：
<dependency>
<groupId>org.apache.kafkagroupId>
<artifactId>kafka-clientsartifactId>
<version>0.10.1.0version>
dependency>这样一来就引入了 kafka 依赖的 jar 包。
我们可以先新建一个 producer ：
package com.signal.kafkaTest;
import java.util.Properties;
import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.Producer;
import org.apache.kafka.clients.producer.ProducerRecord;
public class ProducerTest {
public static void main(String[] args) {
Properties props = new Properties();
props.put("bootstrap.servers", "master:9092,master:9093");
props.put("acks", "all");
props.put("retries", 0);
props.put("batch.size", 16384);
props.put("linger.ms", 1);
props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");
Producer producer = new KafkaProducer(props);
for(int i=0;i<100;i++){
ProducerRecord r = new ProducerRecord("message","key-"+i,"value-"+i);
producer.send(r);
}
producer.close();
}
}
这个我是仿照 API 里写的
这里已经非常清楚了^U^，我就偷工减料了。
然后是 consumer ：
package com.signal.kafkaTest;
import java.util.Arrays;
import java.util.Properties;
import org.apache.kafka.clients.consumer.Consumer;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.KafkaConsumer;
public class ConsumerTest {
public static void main(String[] args) {
Properties props = new Properties();
props.put("bootstrap.servers", "master:9092,master:9093");
props.put("group.id", "test");
props.put("enable.auto.commit", "true");
props.put("auto.commit.interval.ms", "1000");
props.put("session.timeout.ms", "30000");
props.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
Consumer consumer = new KafkaConsumer(props);
consumer.subscribe(Arrays.asList("message"));
while(true){
ConsumerRecords records = consumer.poll(10);
for(ConsumerRecord record : records){
System.out.println("offset=" + record.offset() + ",--key=" + record.key() + ",--value=" + record.value());
}
}
}
}
然后先运行 producer ，再运行 consumer ，控制台输出如下：
offset=208,--key=key-0,--value=value-0
offset=209,--key=key-1,--value=value-1
offset=210,--key=key-2,--value=value-2
offset=211,--key=key-3,--value=value-3
offset=212,--key=key-4,--value=value-4
offset=213,--key=key-5,--value=value-5
offset=214,--key=key-6,--value=value-6
offset=215,--key=key-7,--value=value-7
offset=216,--key=key-8,--value=value-8
offset=217,--key=key-9,--value=value-9
offset=218,--key=key-10,--value=value-10
(此处省略)... 这个就是 kafka 的简单使用了，希望大家好好看看文档，都能很快写出来的。