RocketMQ Streams

RocketMQ Streams is a lightweight stream processing framework, application gains the stream processing ability by depending on RocketMQ Streams as an SDK.

It offers a variety of features:

• Function:
  • One-to-one transform function, such as: filter, map, foreach
  • Aggregate function, such as: sum, min, max, count, aggregate
  • Generating function, such as: flatMap
• Group by aggregate and window aggregate
• Join stream
• Custom serialization

---

Quick Start

This paragraph guides you running a stream processing with RocketMQ Streams.

Run RocketMQ 5.0 locally

RocketMQ quick-start

RocketMQ runs on all major operating systems and requires only a Java JDK version 8 or higher to be installed. To check, run java -version:

$ java -version
java version "1.8.0_121"

1) Download RocketMQ

wget https://archive.apache.org/dist/rocketmq/5.0.0/rocketmq-all-5.0.0-bin-release.zip

# Unpack the release
$ unzip rocketmq-all-5.0.0-bin-release.zip

$ cd rocketmq-all-5.0.0-bin-release/bin

2) Start NameServer

NameServer will be listening at 0.0.0.0:9876, make sure that the port is not used by others on the local machine, and then do as follows.

### start Name Server
$ nohup sh mqnamesrv &

### check whether Name Server is successfully started
$ tail -f ~/logs/rocketmqlogs/namesrv.log
The Name Server boot success...

2) Start Broker

### start Broker
$ nohup sh bin/mqbroker -n localhost:9876 &

### check whether Broker is successfully started, eg: Broker's IP is 192.168.1.2, Broker's name is broker-a
$ tail -f ~/logs/rocketmqlogs/broker.log
The broker[broker-a, 192.169.1.2:10911] boot success...

Build stream processing application

1) Build application in IDE

2) Add RocketMQ Streams dependency

    <dependency>
        <groupId>org.apache.rocketmq</groupId>
        <artifactId>rocketmq-streams</artifactId>
        <version>{current.version}</version>
    </dependency>

3) Build stream processing application

• create topic in RocketMQ before start the stream processing.

sh bin/mqadmin updateTopic -c ${clusterName} -t ${topicName} -r 8 -w 8 -n 127.0.0.1:9876

NOTE: the default clusterName is DefaultCluster in this quick-start doc, changes it with your RocketMQ cluster.

• add your stream processing code, The following is an example. more examples are here.

public static void main(String[] args) {
        StreamBuilder builder = new StreamBuilder("wordCount");

        builder.source("sourceTopic",  total -> {
                    String value = new String(total, StandardCharsets.UTF_8);
                    return new Pair<>(null, value);
                })
                .flatMap((ValueMapperAction<String, List<String>>) value -> {
                    String[] splits = value.toLowerCase().split("\\W+");
                    return Arrays.asList(splits);
                })
                .keyBy(value -> value)
                .count()
                .toRStream()
                .print();

        TopologyBuilder topologyBuilder = builder.build();

        Properties properties = new Properties();
        properties.put(MixAll.NAMESRV_ADDR_PROPERTY, "127.0.0.1:9876");

        RocketMQStream rocketMQStream = new RocketMQStream(topologyBuilder, properties);

        final CountDownLatch latch = new CountDownLatch(1);

        Runtime.getRuntime().addShutdownHook(new Thread("wordcount-shutdown-hook") {
            @Override
            public void run() {
                rocketMQStream.stop();
                latch.countDown();
            }
        });

        try {
            rocketMQStream.start();
            latch.await();
        } catch (final Throwable e) {
            System.exit(1);
        }
        System.exit(0);
    }