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title: Storm RocketMQ layout: documentation documentation: true

Storm/Trident integration for RocketMQ. This package includes the core spout, bolt and trident states that allows a storm topology to either write storm tuples into a topic or read from topics in a storm topology.

Read from Topic

The spout included in this package for reading data from a topic.

RocketMqSpout

To use the RocketMqSpout, you construct an instance of it by specifying a Properties instance which including rocketmq configs. RocketMqSpout uses RocketMQ MQPushConsumer as the default implementation. PushConsumer is a high level consumer API, wrapping the pulling details. Looks like broker push messages to consumer. RocketMqSpout will retry 3(use SpoutConfig.DEFAULT_MESSAGES_MAX_RETRY to change the value) times when messages are failed.

       Properties properties = new Properties();
       properties.setProperty(SpoutConfig.NAME_SERVER_ADDR, nameserverAddr);
       properties.setProperty(SpoutConfig.CONSUMER_GROUP, group);
       properties.setProperty(SpoutConfig.CONSUMER_TOPIC, topic);

       RocketMqSpout spout = new RocketMqSpout(properties);

Write into Topic

The bolt and trident state included in this package for write data into a topic.

TupleToMessageMapper

The main API for mapping Storm tuple to a RocketMQ Message is the org.apache.storm.rocketmq.common.mapper.TupleToMessageMapper interface:

public interface TupleToMessageMapper extends Serializable {
    String getKeyFromTuple(ITuple tuple);
    byte[] getValueFromTuple(ITuple tuple);
}

FieldNameBasedTupleToMessageMapper

storm-rocketmq includes a general purpose TupleToMessageMapper implementation called FieldNameBasedTupleToMessageMapper.

TopicSelector

The main API for selecting topic and tags is the org.apache.storm.rocketmq.common.selector.TopicSelector interface:

public interface TopicSelector extends Serializable {
    String getTopic(ITuple tuple);
    String getTag(ITuple tuple);
}

DefaultTopicSelector/FieldNameBasedTopicSelector

storm-rocketmq includes general purpose TopicSelector implementations called DefaultTopicSelector and FieldNameBasedTopicSelector.

RocketMqBolt

To use the RocketMqBolt, you construct an instance of it by specifying TupleToMessageMapper, TopicSelector and Properties instances. RocketMqBolt send messages async by default. You can change this by invoking withAsync(false).

       TupleToMessageMapper mapper = new FieldNameBasedTupleToMessageMapper("word", "count");
       TopicSelector selector = new DefaultTopicSelector(topic);

       properties = new Properties();
       properties.setProperty(RocketMqConfig.NAME_SERVER_ADDR, nameserverAddr);

       RocketMqBolt insertBolt = new RocketMqBolt()
               .withMapper(mapper)
               .withSelector(selector)
               .withProperties(properties);

Trident State

We support trident persistent state that can be used with trident topologies. To create a RocketMQ persistent trident state you need to initialize it with the TupleToMessageMapper, TopicSelector, Properties instances. See the example below:

       TupleToMessageMapper mapper = new FieldNameBasedTupleToMessageMapper("word", "count");
       TopicSelector selector = new DefaultTopicSelector(topic);

       Properties properties = new Properties();
       properties.setProperty(RocketMqConfig.NAME_SERVER_ADDR, nameserverAddr);

       RocketMqState.Options options = new RocketMqState.Options()
               .withMapper(mapper)
               .withSelector(selector)
               .withProperties(properties);

       StateFactory factory = new RocketMqStateFactory(options);

       TridentTopology topology = new TridentTopology();
       Stream stream = topology.newStream("spout1", spout);

       stream.partitionPersist(factory, fields,
               new RocketMqStateUpdater(), new Fields());