消息队列 -提供上层服务接口

前言

我们之前已经将 数据库 的操作 和文件的操作 都完成了, 但是对于上层调用来说, 并不关心是于数据库中存储数据还是往文件中存储数据, 因此 我们提供一个类, 封装一下 上述俩个类中的操作, 并将这个类 提供给上层调用

封装数据库

package com.example.demo.mqServer.dataCenter;

import com.example.demo.Common.MqException;
import com.example.demo.mqServer.core.Binding;
import com.example.demo.mqServer.core.Exchange;
import com.example.demo.mqServer.core.MSGQueue;
import com.example.demo.mqServer.core.Message;

import java.io.IOException;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;

/*
* 管理所有硬盘上的数据
* 1: 数据库:  交换机 绑定 队列
* 2: 数据文件 : 消息
* 上层逻辑如果需要操作硬盘, 统一通过这个类来使用 , 上层代码不关系当前数据是存储在数据库还是文件中的*/
public class DiskDataCenter {
//    用来管理数据库中的数据
    private DataBaseManager dataBaseManager = new DataBaseManager();
//    用来管理数据文件中的数据
    private MessageFileManager messageFileManager = new MessageFileManager();
//    对上述实例进行初始化
    public void init(){
        dataBaseManager.init();
        messageFileManager.init();
    }
    // 封装交换机操作
    public void  insertExchange(Exchange exchange){
        dataBaseManager.insertExchange(exchange);
    }
    public void deleteExchange(String exchangeName){
        dataBaseManager.deleteExchange(exchangeName);
    }
    public List<Exchange> selectAllExchange(){
      return   dataBaseManager.selectAllExchanges();
    }
    // 封装队列操作
    public void insertQueue(MSGQueue queue){
        dataBaseManager.insertQueue(queue);
    }
    public void deleteQueue(String queueName){
        dataBaseManager.deleteQueue(queueName);
    }
    public List<MSGQueue> selectAllQueue(){
      return   dataBaseManager.selectAllQueues();
    }
    // 封装绑定操作
    public void insertBinding(Binding binding){
        dataBaseManager.insertBinding(binding);
    }
    public void deleteBinding(Binding binding){
        dataBaseManager.deleteBinding(binding);
    }
    public List<Binding> selectAllBinding(){
       return dataBaseManager.selectAllBindings();
    }
    // 封装消息操作
    public void sendMessage(MSGQueue queue, Message message) throws IOException, MqException {
        messageFileManager.sendMessage(queue, message);
    }

    public void deleteMessage(MSGQueue queue, Message message) throws IOException, ClassNotFoundException, MqException {
        messageFileManager.deleteMessage(queue, message);
        // 对于删除消息, 我们要查看是否需要垃圾回收
        if (messageFileManager.checkGC(queue.getName())) {
            messageFileManager.gc(queue);
        }
    }

    public LinkedList<Message> loadAllMessageFromQueue(String queueName) throws IOException, MqException, ClassNotFoundException {
        return messageFileManager.loadAllMessageFromQueue(queueName);
    }

}

封装内存操作

上面我们完成的都是往硬盘上面保存数据的操作, 无论是 往数据库中添加 队列 交换机 类, 还是往文件存储消息 都是针对硬盘上的操作 ,所以我们现在写关于内存的操作

内存的设计思想

我们关于交换机和队列, 我们都使用哈希表来存储 key 是各自的名字也是主键, value 是对应的 交换机和队列
绑定:使用嵌套的哈希表来存储 , 第一个key是 交换机名称, 第二个key 是队列名称
消息: 使用哈希表来存储, key 是消息ID , value 是消息对象(每一个消息都是一个哈希表)
队列和消息之前的关系: 使用嵌套的哈希表来存储 , key是队列名, value是一个LinkedList 里面存放的消息
还有关于确认应答: 我们采用嵌套的哈希表来存储 , key是队列名, value 是哈希表,( key是消息ID, value是消息)

应答模式

我们这里实现的MQ消息队列, 支持俩种应答模式
第一种: 自动应答, 也就是说当消费者取走了元素, 就当做这个消息被应答了, 此时这个消息就可以被当做成了垃圾了
第二种: 确认应答 : 消费者取走了元素, 还不能被当做是应答了, 必须消费者主动调用一个确认应答方法, 此时才能认为这个消息无用了, 可以删除了

代码实现

package com.example.demo.mqServer.dataCenter;

import com.example.demo.Common.MqException;
import com.example.demo.mqServer.core.Binding;
import com.example.demo.mqServer.core.Exchange;
import com.example.demo.mqServer.core.MSGQueue;
import com.example.demo.mqServer.core.Message;

import java.io.IOException;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;

// 使用这个类来统一管理内存中的数据
// 处理各种映射关系
// 该类提供的方法, 可能在多线程情况下处理, 所以使用线程安全的哈希表
public class MemoryDataCenter {

    // 根据交换机名称来获取交换机对象 , key 是 exchangeName, value 是 Exchange 对象
    private ConcurrentHashMap<String , Exchange> exchangeMap = new ConcurrentHashMap<>();
    // 根据队列名来获取队列对象 , key 是 queueName, value 是 MSGQueue 对象
    private ConcurrentHashMap<String , MSGQueue> queueMap =new ConcurrentHashMap<>();
    //根据交换机名, 和队列名 来获取 绑定对象 ,  第一个 key 是 exchangeName, 第二个 key 是 queueName
    private ConcurrentHashMap<String , ConcurrentHashMap<String , Binding>> bindingsMap = new ConcurrentHashMap<>();
    //根据消息名称 来获取 消息对象,  key 是 messageId, value 是 Message 对象
   private ConcurrentHashMap<String , Message> messageMap = new ConcurrentHashMap<>();
    // 根据队列名称, 来获取消息列表 , key 是 队列名称, value 是 Message 对象
    private ConcurrentHashMap<String, LinkedList<Message>> queueMessageMap = new ConcurrentHashMap<>();
    // 手动应答 , 第一个 key 是 queueName, 第二个 key 是 messageId ,
    private ConcurrentHashMap<String, ConcurrentHashMap<String, Message>> queueMessageWaitAckMap = new ConcurrentHashMap<>();

    public void insertExchange(Exchange exchange) {
        exchangeMap.put(exchange.getName(),exchange);
        System.out.println("[MemoryDataCenter] 新交换机添加成功! exchangeName=" + exchange.getName());
    }
    public Exchange getExchange(String exchangeName) {
        return exchangeMap.get(exchangeName);
    }

    public void deleteExchange(String exchangeName) {
        exchangeMap.remove(exchangeName);
        System.out.println("[MemoryDataCenter] 交换机删除成功! exchangeName=" + exchangeName);
    }

    public void insertQueue(MSGQueue queue) {
        queueMap.put(queue.getName(),queue);
        System.out.println("[MemoryDataCenter] 新队列添加成功! queueName=" + queue.getName());
    }

    public MSGQueue getQueue(String queueName) {
        return queueMap.get(queueName);
    }

    public void deleteQueue(String queueName) {
        queueMap.remove(queueName);
        System.out.println("[MemoryDataCenter] 队列删除成功! queueName=" + queueName);
    }
    public void insertBinding(Binding binding) throws MqException {
        ConcurrentHashMap<String , Binding> bindingMap = bindingsMap.get(binding.getExchangeName());
        if (bindingMap == null){
            bindingMap = new ConcurrentHashMap<>();
            bindingsMap.put(binding.getExchangeName(), bindingMap);
        }
        // 再根据 queueName 查一下. 如果已经存在, 就抛出异常. 不存在才能插入.
        synchronized (binding){
            if (bindingMap.get(binding.getMsgQueueName()) != null) {
                throw new MqException("[MemoryDataCenter] 绑定已经存在! exchangeName=" + binding.getExchangeName() +
                        ", queueName=" + binding.getMsgQueueName());
            }
            bindingMap.put(binding.getMsgQueueName(), binding);
        }
        System.out.println("[MemoryDataCenter] 新绑定添加成功! exchangeName=" + binding.getExchangeName()
                + ", queueName=" + binding.getMsgQueueName());
    }

    // 获取绑定, 写两个版本:
    // 1. 根据 exchangeName 和 queueName 确定唯一一个 Binding
    // 2. 根据 exchangeName 获取到所有的 Binding
    public Binding getBinding(String exchangeName, String queueName) {
        ConcurrentHashMap<String , Binding> bindingMap = bindingsMap.get(exchangeName);
        if (bindingMap == null){
            return null;
        }
        return bindingMap.get(queueName);
    }

    public ConcurrentHashMap<String, Binding> getBindings(String exchangeName) {
        return bindingsMap.get(exchangeName);
    }

    public void deleteBinding(Binding binding) throws MqException {
        ConcurrentHashMap<String , Binding> bindingMap = bindingsMap.get(binding.getExchangeName());
        if (bindingMap == null){
            // 该交换机没有绑定任何队列. 报错.
            throw new MqException("[MemoryDataCenter] 绑定不存在! exchangeName=" + binding.getExchangeName()
                    + ", queueName=" + binding.getMsgQueueName());
        }
        bindingMap.remove(binding.getMsgQueueName());
        System.out.println("[MemoryDataCenter] 绑定删除成功! exchangeName=" + binding.getExchangeName()
                + ", queueName=" + binding.getMsgQueueName());
    }

    // 添加消息
    public void addMessage(Message message) {
        messageMap.put(message.getMessageId(),message);
    }

    // 根据 id 查询消息
    public Message getMessage(String messageId) {
      return   messageMap.get(messageId);
    }

    // 根据 id 删除消息
    public void removeMessage(String messageId) {
        messageMap.remove(messageId);
    }

    // 发送消息到指定队列
    public void sendMessage(MSGQueue queue, Message message) {
        // 把消息放到对应的队列数据结构中.
        // 先根据队列的名字, 找到该队列对应的消息链表.
        LinkedList<Message> messages = queueMessageMap.computeIfAbsent(queue.getName(), k -> new LinkedList<>());
        // 再把数据加到 messages 里面
        synchronized (messages) {
            messages.add(message);
        }
        // 在这里把该消息也往消息中心中插入一下. 假设如果 message 已经在消息中心存在, 重复插入也没关系.
        // 主要就是相同 messageId, 对应的 message 的内容一定是一样的. (服务器代码不会对 Message 内容做修改 basicProperties 和 body)
        addMessage(message);
        System.out.println("[MemoryDataCenter] 消息被投递到队列中! messageId=" + message.getMessageId());
    }

    // 从队列中取消息
    public Message pollMessage(String queueName) {
        // 根据队列名, 查找一下, 对应的队列的消息链表.
        LinkedList<Message> messages = queueMessageMap.get(queueName);
        if (messages == null) {
            return null;
        }
        synchronized (messages) {
            // 如果没找到, 说明队列中没有任何消息.
            if (messages.size() == 0) {
                return null;
            }
            // 链表中有元素, 就进行头删.
            Message currentMessage = messages.remove(0);
            System.out.println("[MemoryDataCenter] 消息从队列中取出! messageId=" + currentMessage.getMessageId());
            return currentMessage;
        }
    }

    // 获取指定队列中消息的个数
    public int getMessageCount(String queueName) {
        LinkedList<Message> messages = queueMessageMap.get(queueName);
        if (messages == null) {
            // 队列中没有消息
            return 0;
        }
        synchronized (messages) {
            return messages.size();
        }
    }

    // 添加未确认的消息
    public void addMessageWaitAck(String queueName, Message message) {
        ConcurrentHashMap<String, Message> messageHashMap = queueMessageWaitAckMap.computeIfAbsent(queueName,
                k -> new ConcurrentHashMap<>());
        messageHashMap.put(message.getMessageId(), message);
        System.out.println("[MemoryDataCenter] 消息进入待确认队列! messageId=" + message.getMessageId());
    }

    // 删除未确认的消息(消息已经确认了)
    public void removeMessageWaitAck(String queueName, String messageId) {
        ConcurrentHashMap<String, Message> messageHashMap = queueMessageWaitAckMap.computeIfAbsent(queueName,
                k -> new ConcurrentHashMap<>());
        if (messageHashMap == null)return;
        messageHashMap.remove(messageId);
    }

    // 获取指定的未确认的消息
    public Message getMessageWaitAck(String queueName, String messageId) {
        ConcurrentHashMap<String, Message> messageHashMap = queueMessageWaitAckMap.computeIfAbsent(queueName,
                k -> new ConcurrentHashMap<>());
        if (messageHashMap == null)return null;
        return messageHashMap.get(messageId);
    }

    // 这个方法就是从硬盘上读取数据, 把硬盘中之前持久化存储的各个维度的数据都恢复到内存中.
    public void recovery(DiskDataCenter diskDataCenter) throws IOException, MqException, ClassNotFoundException {
      List<Exchange>  exchanges = diskDataCenter.selectAllExchange();
      exchangeMap.clear();
      for (Exchange exchange:exchanges) {
            exchangeMap.put(exchange.getName(),exchange);
      }
      List<MSGQueue> queues = diskDataCenter.selectAllQueue();
      queueMap.clear();
      for (MSGQueue q :queues) {
         queueMap.put(q.getName(),q);
      }
      List<Binding> bindings = diskDataCenter.selectAllBinding();
      bindingsMap.clear();
        for (Binding binding : bindings) {
            ConcurrentHashMap<String, Binding> bindingMap = bindingsMap.computeIfAbsent(binding.getExchangeName(),
                    k -> new ConcurrentHashMap<>());
            bindingMap.put(binding.getMsgQueueName(), binding);
        }

        // 4. 恢复所有的消息数据
        //    遍历所有的队列, 根据每个队列的名字, 获取到所有的消息.
        messageMap.clear();
        queueMessageMap.clear();
        for (MSGQueue queue : queues) {
            LinkedList<Message> messages = diskDataCenter.loadAllMessageFromQueue(queue.getName());
            queueMessageMap.put(queue.getName(), messages);
            for (Message message : messages) {
                messageMap.put(message.getMessageId(), message);
            }
        }
        // 注意!! 针对 "未确认的消息" 这部分内存中的数据, 不需要从硬盘恢复. 之前考虑硬盘存储的时候, 也没设定这一块.
        // 一旦在等待 ack 的过程中, 服务器重启了, 此时这些 "未被确认的消息", 就恢复成 "未被取走的消息" .
        // 这个消息在硬盘上存储的时候, 就是当做 "未被取走"

    }



}

测试代码

package com.example.demo.mqServer.dataCenter;

import com.example.demo.Common.MqException;
import com.example.demo.MqApplication;
import com.example.demo.mqServer.core.*;
import org.apache.tomcat.util.http.fileupload.FileUtils;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.test.context.SpringBootTest;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;

import static org.junit.jupiter.api.Assertions.*;
@SpringBootTest
class MemoryDataCenterTest {
    private MemoryDataCenter memoryDataCenter = null;

    @BeforeEach
    public void setUp() {
        memoryDataCenter = new MemoryDataCenter();
    }

    @AfterEach
    public void tearDown() {
        memoryDataCenter = null;
    }
    // 创建一个测试交换机
    private Exchange createTestExchange(String exchangeName) {
        Exchange exchange = new Exchange();
        exchange.setName(exchangeName);
        exchange.setType(ExchangeType.direct);
        exchange.setAutoDelete(false);
        exchange.setDurable(true);
        return exchange;
    }

    // 创建一个测试队列
    private MSGQueue createTestQueue(String queueName) {
        MSGQueue queue = new MSGQueue();
        queue.setName(queueName);
        queue.setDurable(true);
        queue.setExclusive(false);
        queue.setAutoDelete(false);
        return queue;
    }

    // 针对交换机进行测试
    @Test
    public void testExchange() {
        // 1. 先构造一个交换机并插入.
        Exchange expectedExchange = createTestExchange("testExchange");
        memoryDataCenter.insertExchange(expectedExchange);
        // 2. 查询出这个交换机, 比较结果是否一致. 此处直接比较这俩引用指向同一个对象.
        Exchange actualExchange = memoryDataCenter.getExchange("testExchange");
        Assertions.assertEquals(expectedExchange, actualExchange);
        // 3. 删除这个交换机
        memoryDataCenter.deleteExchange("testExchange");
        // 4. 再查一次, 看是否就查不到了
        actualExchange = memoryDataCenter.getExchange("testExchange");
        Assertions.assertNull(actualExchange);
    }
    // 针对队列进行测试
    @Test
    public void testQueue() {
        // 1. 构造一个队列, 并插入
        MSGQueue expectedQueue = createTestQueue("testQueue");
        memoryDataCenter.insertQueue(expectedQueue);
        // 2. 查询这个队列, 并比较
        MSGQueue actualQueue = memoryDataCenter.getQueue("testQueue");
        Assertions.assertEquals(expectedQueue, actualQueue);
        // 3. 删除这个队列
        memoryDataCenter.deleteQueue("testQueue");
        // 4. 再次查询队列, 看是否能查到
        actualQueue = memoryDataCenter.getQueue("testQueue");
        Assertions.assertNull(actualQueue);
    }
    // 针对绑定进行测试
    @Test
    public void testBinding() throws MqException {
        Binding expectedBinding = new Binding();
        expectedBinding.setExchangeName("testExchange");
        expectedBinding.setMsgQueueName("testQueue");
        expectedBinding.setBindingKey("testBindingKey");
        memoryDataCenter.insertBinding(expectedBinding);

        Binding actualBinding = memoryDataCenter.getBinding("testExchange", "testQueue");
        Assertions.assertEquals(expectedBinding, actualBinding);

        ConcurrentHashMap<String, Binding> bindingMap = memoryDataCenter.getBindings("testExchange");
        Assertions.assertEquals(1, bindingMap.size());
        Assertions.assertEquals(expectedBinding, bindingMap.get("testQueue"));

        memoryDataCenter.deleteBinding(expectedBinding);

        actualBinding = memoryDataCenter.getBinding("testExchange", "testQueue");
        Assertions.assertNull(actualBinding);
    }
    // 测试消息的增删查
    private Message createTestMessage(String content) {
        Message message = Message.createMessageWithId("testRoutingKey", null, content.getBytes());
        return message;
    }

    @Test
    public void testMessage() {
        Message expectedMessage = createTestMessage("testMessage");
        memoryDataCenter.addMessage(expectedMessage);

        Message actualMessage = memoryDataCenter.getMessage(expectedMessage.getMessageId());
        Assertions.assertEquals(expectedMessage, actualMessage);

        memoryDataCenter.removeMessage(expectedMessage.getMessageId());

        actualMessage = memoryDataCenter.getMessage(expectedMessage.getMessageId());
        Assertions.assertNull(actualMessage);
    }
    @Test
    public void testSendMessage() {
        // 1. 创建一个队列, 创建 10 条消息, 把这些消息都插入队列中.
        MSGQueue queue = createTestQueue("testQueue");
        List<Message> expectedMessages = new ArrayList<>();
        for (int i = 0; i < 10; i++) {
            Message message = createTestMessage("testMessage" + i);
            memoryDataCenter.sendMessage(queue, message);
            expectedMessages.add(message);
        }

        // 2. 从队列中取出这些消息.
        List<Message> actualMessages = new ArrayList<>();
        while (true) {
            Message message = memoryDataCenter.pollMessage("testQueue");
            if (message == null) {
                break;
            }
            actualMessages.add(message);
        }

        // 3. 比较取出的消息和之前的消息是否一致.
        Assertions.assertEquals(expectedMessages.size(), actualMessages.size());
        for (int i = 0; i < expectedMessages.size(); i++) {
            Assertions.assertEquals(expectedMessages.get(i), actualMessages.get(i));
        }
    }
    @Test
    public void testMessageWaitAck() {
        Message expectedMessage = createTestMessage("expectedMessage");
        memoryDataCenter.addMessageWaitAck("testQueue", expectedMessage);

        Message actualMessage = memoryDataCenter.getMessageWaitAck("testQueue", expectedMessage.getMessageId());
        Assertions.assertEquals(expectedMessage, actualMessage);

        memoryDataCenter.removeMessageWaitAck("testQueue", expectedMessage.getMessageId());
        actualMessage = memoryDataCenter.getMessageWaitAck("testQueue", expectedMessage.getMessageId());
        Assertions.assertNull(actualMessage);
    }
    @Test
    public void testRecovery() throws IOException, MqException, ClassNotFoundException {
        // 由于后续需要进行数据库操作, 依赖 MyBatis. 就需要先启动 SpringApplication, 这样才能进行后续的数据库操作.
        MqApplication.context = SpringApplication.run(MqApplication.class);

        // 1. 在硬盘上构造好数据
        DiskDataCenter diskDataCenter = new DiskDataCenter();
        diskDataCenter.init();

        // 构造交换机
        Exchange expectedExchange = createTestExchange("testExchange");
        diskDataCenter.insertExchange(expectedExchange);

        // 构造队列
        MSGQueue expectedQueue = createTestQueue("testQueue");
        diskDataCenter.insertQueue(expectedQueue);

        // 构造绑定
        Binding expectedBinding = new Binding();
        expectedBinding.setExchangeName("testExchange");
        expectedBinding.setMsgQueueName("testQueue");
        expectedBinding.setBindingKey("testBindingKey");
        diskDataCenter.insertBinding(expectedBinding);

        // 构造消息
        Message expectedMessage = createTestMessage("testContent");
        diskDataCenter.sendMessage(expectedQueue, expectedMessage);

        // 2. 执行恢复操作
        memoryDataCenter.recovery(diskDataCenter);

        // 3. 对比结果
        Exchange actualExchange = memoryDataCenter.getExchange("testExchange");
        Assertions.assertEquals(expectedExchange.getName(), actualExchange.getName());
        Assertions.assertEquals(expectedExchange.getType(), actualExchange.getType());
        Assertions.assertEquals(expectedExchange.isDurable(), actualExchange.isDurable());
        Assertions.assertEquals(expectedExchange.isAutoDelete(), actualExchange.isAutoDelete());

        MSGQueue actualQueue = memoryDataCenter.getQueue("testQueue");
        Assertions.assertEquals(expectedQueue.getName(), actualQueue.getName());
        Assertions.assertEquals(expectedQueue.isDurable(), actualQueue.isDurable());
        Assertions.assertEquals(expectedQueue.isAutoDelete(), actualQueue.isAutoDelete());
        Assertions.assertEquals(expectedQueue.isExclusive(), actualQueue.isExclusive());

        Binding actualBinding = memoryDataCenter.getBinding("testExchange", "testQueue");
        Assertions.assertEquals(expectedBinding.getExchangeName(), actualBinding.getExchangeName());
        Assertions.assertEquals(expectedBinding.getMsgQueueName(), actualBinding.getMsgQueueName());
        Assertions.assertEquals(expectedBinding.getBindingKey(), actualBinding.getBindingKey());

        Message actualMessage = memoryDataCenter.pollMessage("testQueue");
        Assertions.assertEquals(expectedMessage.getMessageId(), actualMessage.getMessageId());
        Assertions.assertEquals(expectedMessage.getRoutingKey(), actualMessage.getRoutingKey());
        Assertions.assertEquals(expectedMessage.getDeliverMode(), actualMessage.getDeliverMode());
        Assertions.assertArrayEquals(expectedMessage.getBody(), actualMessage.getBody());

        // 4. 清理硬盘的数据, 把整个 data 目录里的内容都删掉(包含了 meta.db 和 队列的目录).
        MqApplication.context.close();
        File dataDir = new File("./data");
        FileUtils.deleteDirectory(dataDir);
    }
}