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RocketMQ-Flink

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RocketMQ integration for Apache Flink. This module includes the RocketMQ source and sink that allows a flink job to either write messages into a topic or read from topics in a flink job.

RocketMQSourceFunction

To use the RocketMQSourceFunction, you construct an instance of it by specifying a KeyValueDeserializationSchema instance and a Properties instance which including rocketmq configs. RocketMQSourceFunction(KeyValueDeserializationSchema<OUT> schema, Properties props) The RocketMQSourceFunction is based on RocketMQ pull consumer mode, and provides exactly once reliability guarantees when checkpoints are enabled. Otherwise, the source doesn't provide any reliability guarantees.

KeyValueDeserializationSchema

The main API for deserializing topic and tags is the org.apache.rocketmq.flink.legacy.common.serialization.KeyValueDeserializationSchema interface. rocketmq-flink includes general purpose KeyValueDeserializationSchema implementations called SimpleKeyValueDeserializationSchema.

public interface KeyValueDeserializationSchema<T> extends ResultTypeQueryable<T>, Serializable {
    T deserializeKeyAndValue(byte[] key, byte[] value);
}

RocketMQSink

To use the RocketMQSink, you construct an instance of it by specifying KeyValueSerializationSchema & TopicSelector instances and a Properties instance which including rocketmq configs. RocketMQSink(KeyValueSerializationSchema<IN> schema, TopicSelector<IN> topicSelector, Properties props) The RocketMQSink provides at-least-once reliability guarantees when checkpoints are enabled and withBatchFlushOnCheckpoint(true) is set. Otherwise, the sink reliability guarantees depends on rocketmq producer's retry policy, for this case, the messages sending way is sync by default, but you can change it by invoking withAsync(true).

KeyValueSerializationSchema

The main API for serializing topic and tags is the org.apache.rocketmq.flink.legacy.common.serialization.KeyValueSerializationSchema interface. rocketmq-flink includes general purpose KeyValueSerializationSchema implementations called SimpleKeyValueSerializationSchema.

public interface KeyValueSerializationSchema<T> extends Serializable {

    byte[] serializeKey(T tuple);

    byte[] serializeValue(T tuple);
}

TopicSelector

The main API for selecting topic and tags is the org.apache.rocketmq.flink.legacy.common.selector.TopicSelector interface. rocketmq-flink includes general purpose TopicSelector implementations called DefaultTopicSelector and SimpleTopicSelector.

public interface TopicSelector<T> extends Serializable {

    String getTopic(T tuple);

    String getTag(T tuple);
}

Examples

The following is an example which receive messages from RocketMQ brokers and send messages to broker after processing.

StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();

       // enable checkpoint
       env.enableCheckpointing(3000);

       Properties consumerProps = new Properties();
       consumerProps.setProperty(RocketMQConfig.NAME_SERVER_ADDR, "localhost:9876");
       consumerProps.setProperty(RocketMQConfig.CONSUMER_GROUP, "c002");
       consumerProps.setProperty(RocketMQConfig.CONSUMER_TOPIC, "flink-source2");

       Properties producerProps = new Properties();
       producerProps.setProperty(RocketMQConfig.NAME_SERVER_ADDR, "localhost:9876");

       RocketMQSourceFunction<Map<Object,Object>> source = new RocketMQSourceFunction(
               new SimpleKeyValueDeserializationSchema("id", "address"), consumerProps);
       // use group offsets.
       // If there is no committed offset,consumer would start from the latest offset.
       source.setStartFromGroupOffsets(OffsetResetStrategy.LATEST);
       env.addSource(source)
           .name("rocketmq-source")
           .setParallelism(2)
           .process(new ProcessFunction<Map<Object, Object>, Map<Object, Object>>() {
               @Override
               public void processElement(
                       Map<Object, Object> in,
                       Context ctx,
                       Collector<Map<Object, Object>> out) {
                   HashMap result = new HashMap();
                   result.put("id", in.get("id"));
                   String[] arr = in.get("address").toString().split("\\s+");
                   result.put("province", arr[arr.length - 1]);
                   out.collect(result);
               }
           })
           .name("upper-processor")
           .setParallelism(2)
           .process(new ProcessFunction<Map<Object, Object>, Message>() {
               @Override
               public void processElement(Map<Object, Object> value, Context ctx, Collector<Message> out) {
                   String jsonString = JSONObject.toJSONString(value);
                   Message message =
                           new Message(
                                   "flink-sink2",
                                   "",
                                   jsonString.getBytes(StandardCharsets.UTF_8));
                   out.collect(message);
               }
           })
           .addSink(new RocketMQSink(producerProps).withBatchFlushOnCheckpoint(true))
           .name("rocketmq-sink")
           .setParallelism(2);

       try {
           env.execute("rocketmq-flink-example");
       } catch (Exception e) {
           e.printStackTrace();
       }

Configurations

The following configurations are all from the class org.apache.rocketmq.flink.legacy.RocketMQConfig.

Producer Configurations

NAME DESCRIPTION DEFAULT
nameserver.address name server address Required null
nameserver.poll.interval name server poll topic info interval 30000
brokerserver.heartbeat.interval broker server heartbeat interval 30000
producer.group producer group UUID.randomUUID().toString()
producer.retry.times producer send messages retry times 3
producer.timeout producer send messages timeout 3000

Consumer Configurations

NAME DESCRIPTION DEFAULT
nameserver.address name server address Required null
nameserver.poll.interval name server poll topic info interval 30000
brokerserver.heartbeat.interval broker server heartbeat interval 30000
consumer.group consumer group Required null
consumer.topic consumer topic Required null
consumer.tag consumer topic tag *
consumer.offset.persist.interval auto commit offset interval 5000
consumer.pull.thread.pool.size consumer pull thread pool size 20
consumer.batch.size consumer messages batch size 32
consumer.delay.when.message.not.found the delay time when messages were not found 10

Consumer Strategy

RocketMQSourceFunction<String> source = new RocketMQSourceFunction<>(
        new SimpleStringDeserializationSchema(), props);
HashMap<MessageQueue, Long> brokerMap = new HashMap<>();
brokerMap.put(new MessageQueue("tp_driver_tag_sync_back", "broker-a", 1), 201L);
brokerMap.put(new MessageQueue("tp_driver_tag_sync_back", "broker-c", 3), 123L);
source.setStartFromSpecificOffsets(brokerMap);

RocketMQSourceFunction offer five initialization policies

  • setStartFromEarliest
  • setStartFromLatest
  • setStartFromTimeStamp with timestamp
  • setStartFromGroupOffsets with OffsetResetStrategy
  • setStartFromSpecificOffsets
STRATEGY DESCRIPTION
EARLIEST consume from the earliest offset after restart with no state
LATEST consume from the latest offset after restart with no state
TIMESTAMP consume from the closest timestamp of data in each broker's queue
GROUP_OFFSETS with LATEST If broker has the committed offset then consume from the next else consume from the latest offset
GROUP_OFFSETS with EARLIEST If broker has the committed offset ,consume from the next ,otherwise consume from the earlist offset.It's useful when server expand broker
SPECIFIC_OFFSETS consumer from the specificOffsets in broker's queues.Group offsets will be returned from those broker's queues whose didn't be specified

Attention

Only if Flink job starts with none state, these strategies are effective. If the job recovers from the checkpoint, the offset would intialize from the stored data.

RocketMQ SQL Connector

How to create a RocketMQ table

The example below shows how to create a RocketMQ table:

CREATE TABLE rocketmq_source (
  `user_id` BIGINT,
  `item_id` BIGINT,
  `behavior` STRING
) WITH (
  'connector' = 'rocketmq',
  'topic' = 'user_behavior',
  'consumerGroup' = 'behavior_consumer_group',
  'nameServerAddress' = '127.0.0.1:9876'
);

CREATE TABLE rocketmq_sink (
  `user_id` BIGINT,
  `item_id` BIGINT,
  `behavior` STRING
) WITH (
  'connector' = 'rocketmq',
  'topic' = 'user_behavior',
  'produceGroup' = 'behavior_produce_group',
  'nameServerAddress' = '127.0.0.1:9876'
);

Available Metadata

The following connector metadata can be accessed as metadata columns in a table definition.

The R/W column defines whether a metadata field is readable (R) and/or writable (W). Read-only columns must be declared VIRTUAL to exclude them during an INSERT INTO operation.

KEY DATA TYPE DESCRIPTION DEFAULT
topic STRING NOT NULL Topic name of the RocketMQ record. R

The extended CREATE TABLE example demonstrates the syntax for exposing these metadata fields:

CREATE TABLE rocketmq_source (
  `topic` STRING METADATA VIRTUAL,
  `user_id` BIGINT,
  `item_id` BIGINT,
  `behavior` STRING
) WITH (
  'connector' = 'rocketmq',
  'topic' = 'user_behavior',
  'consumerGroup' = 'behavior_consumer_group',
  'nameServerAddress' = '127.0.0.1:9876'
);

License

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.