rocketmq實現分散式事務，是指訊息是有狀態的, 目前的3.5.8中沒有，當時在@李戰輝大神之前的某個分支中有簡單的實現

本人建議，如何解決分散式事務呢？ 就是別有這種業務啊。別劃分99%去解決1%可能出現的問題。當然公司發展的階段不同，目標也不會相同。

A呼叫B，A先broker發了一條訊息， A本地開啟事務,執行完本地方法，先broker傳送確認訊息。

B從broker中訂閱訊息，來執行訊息。

0.註冊查詢本地事務Listener

/**
 * 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.
 */
package com.alibaba.rocketmq.example.transaction;

import com.alibaba.rocketmq.client.producer.LocalTransactionState;
import com.alibaba.rocketmq.client.producer.TransactionCheckListener;
import com.alibaba.rocketmq.common.message.MessageExt;

import java.util.concurrent.atomic.AtomicInteger;


public class TransactionCheckListenerImpl implements TransactionCheckListener {
    private AtomicInteger transactionIndex = new AtomicInteger(0);

    /**
     * 主動檢查機制
     */
    @Override
    public LocalTransactionState checkLocalTransactionState(MessageExt msg) {
        System.out.println("server checking TrMsg " + msg.toString());

        int value = transactionIndex.getAndIncrement();
        if ((value % 6) == 0) {
            throw new RuntimeException("Could not find db");
        } else if ((value % 5) == 0) {
            return LocalTransactionState.ROLLBACK_MESSAGE;
        } else if ((value % 4) == 0) {
            return LocalTransactionState.COMMIT_MESSAGE;
        }

        return LocalTransactionState.UNKNOW;
    }
}
 

1.實現本地事務邏輯LocalTransactionExecuter

/**
 * 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.
 */
package com.alibaba.rocketmq.example.transaction;

import com.alibaba.rocketmq.client.producer.LocalTransactionExecuter;
import com.alibaba.rocketmq.client.producer.LocalTransactionState;
import com.alibaba.rocketmq.common.message.Message;

import java.util.concurrent.atomic.AtomicInteger;

public class TransactionExecuterImpl implements LocalTransactionExecuter {
    private AtomicInteger transactionIndex = new AtomicInteger(1);

    /**
     * 執行本地業務邏輯
     */
    @Override
    public LocalTransactionState executeLocalTransactionBranch(final Message msg, final Object arg) {
        int value = transactionIndex.getAndIncrement();

        if (value == 0) {
            throw new RuntimeException("Could not find db");
        } else if ((value % 5) == 0) {
            return LocalTransactionState.ROLLBACK_MESSAGE;
        } else if ((value % 4) == 0) {
            return LocalTransactionState.COMMIT_MESSAGE;
        }

        return LocalTransactionState.UNKNOW;
    }
}
 

2.檢視呼叫方式

/**
 * 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.
 */
package com.alibaba.rocketmq.example.transaction;

import com.alibaba.rocketmq.client.exception.MQClientException;
import com.alibaba.rocketmq.client.producer.SendResult;
import com.alibaba.rocketmq.client.producer.TransactionCheckListener;
import com.alibaba.rocketmq.client.producer.TransactionMQProducer;
import com.alibaba.rocketmq.common.message.Message;
import com.alibaba.rocketmq.remoting.common.RemotingHelper;

import java.io.UnsupportedEncodingException;

public class TransactionProducer {
    public static void main(String[] args) throws MQClientException, InterruptedException {

        TransactionCheckListener transactionCheckListener = new TransactionCheckListenerImpl();
        TransactionMQProducer producer = new TransactionMQProducer("please_rename_unique_group_name");

        producer.setCheckThreadPoolMinSize(2);

        producer.setCheckThreadPoolMaxSize(2);

        producer.setCheckRequestHoldMax(2000);
        producer.setTransactionCheckListener(transactionCheckListener);
        producer.start();

        String[] tags = new String[]{"TagA", "TagB", "TagC", "TagD", "TagE"};
        TransactionExecuterImpl tranExecuter = new TransactionExecuterImpl();
        for (int i = 0; i < 100; i++) {
            try {
                Message msg =
                        new Message("TopicTest", tags[i % tags.length], "KEY" + i,
                                ("Hello RocketMQ " + i).getBytes(RemotingHelper.DEFAULT_CHARSET));
                SendResult sendResult = producer.sendMessageInTransaction(msg, tranExecuter, null);
                System.out.println(sendResult);

                Thread.sleep(10);
            } catch (MQClientException e) {
                e.printStackTrace();
            } catch (UnsupportedEncodingException e) {
                e.printStackTrace();
            }
        }

        for (int i = 0; i < 100000; i++) {
            Thread.sleep(1000);
        }

        producer.shutdown();

    }
}
 

3.檢視rocketmq實現邏輯

public TransactionSendResult sendMessageInTransaction(final Message msg, final LocalTransactionExecuter tranExecuter, final Object arg)
            throws MQClientException {
        if (null == tranExecuter) {
            throw new MQClientException("tranExecutor is null", null);
        }
        Validators.checkMessage(msg, this.defaultMQProducer);

        SendResult sendResult = null;
        MessageAccessor.putProperty(msg, MessageConst.PROPERTY_TRANSACTION_PREPARED, "true");
        MessageAccessor.putProperty(msg, MessageConst.PROPERTY_PRODUCER_GROUP, this.defaultMQProducer.getProducerGroup());
        try {
            sendResult = this.send(msg);
        } catch (Exception e) {
            throw new MQClientException("send message Exception", e);
        }

        LocalTransactionState localTransactionState = LocalTransactionState.UNKNOW;
        Throwable localException = null;
        switch (sendResult.getSendStatus()) {
            case SEND_OK: {
                try {
                    if (sendResult.getTransactionId() != null) {
                        msg.putUserProperty("__transactionId__", sendResult.getTransactionId());
                    }
                    localTransactionState = tranExecuter.executeLocalTransactionBranch(msg, arg);
                    if (null == localTransactionState) {
                        localTransactionState = LocalTransactionState.UNKNOW;
                    }

                    if (localTransactionState != LocalTransactionState.COMMIT_MESSAGE) {
                        log.info("executeLocalTransactionBranch return {}", localTransactionState);
                        log.info(msg.toString());
                    }
                } catch (Throwable e) {
                    log.info("executeLocalTransactionBranch exception", e);
                    log.info(msg.toString());
                    localException = e;
                }
            }
            break;
            case FLUSH_DISK_TIMEOUT:
            case FLUSH_SLAVE_TIMEOUT:
            case SLAVE_NOT_AVAILABLE:
                localTransactionState = LocalTransactionState.ROLLBACK_MESSAGE;
                break;
            default:
                break;
        }

        try {
            this.endTransaction(sendResult, localTransactionState, localException);
        } catch (Exception e) {
            log.warn("local transaction execute " + localTransactionState + ", but end broker transaction failed", e);
        }

        TransactionSendResult transactionSendResult = new TransactionSendResult();
        transactionSendResult.setSendStatus(sendResult.getSendStatus());
        transactionSendResult.setMessageQueue(sendResult.getMessageQueue());
        transactionSendResult.setMsgId(sendResult.getMsgId());
        transactionSendResult.setQueueOffset(sendResult.getQueueOffset());
        transactionSendResult.setTransactionId(sendResult.getTransactionId());
        transactionSendResult.setLocalTransactionState(localTransactionState);
        return transactionSendResult;
    }