52.源代碼解讀-RocketMQ消息寫入機制

一. 前言

RocketMQ採用內存和磁盤存儲來存儲消息。那現在來分析一下消息存儲的流程

二. 代碼流程

在Broker啓動的時候會拉起相關服務
流程如下：

流程圖引用網址
http://blog.csdn.net/akfly/article/details/53447000

三. 代碼流程

由於是Broker來存儲消息，那麼消息入口的代碼應該是在Broker裏面，而Broker的入口是BrokerStartup，以及重要的BrokerController。
具體流程可以參考Broker啓動源代碼分析。

Broker啓動流程

以發送消息爲例

1. Broker啓動註冊發送消息處理器

Broker啓動的時候，會註冊一個SendMessageProcesser來響應netty的發送消息請求，如下：

public void registerProcessor() {
        /**
         * SendMessageProcessor
         */
        SendMessageProcessor sendProcessor = new SendMessageProcessor(this);
        sendProcessor.registerSendMessageHook(sendMessageHookList);
        sendProcessor.registerConsumeMessageHook(consumeMessageHookList);

        this.remotingServer.registerProcessor(RequestCode.SEND_MESSAGE, sendProcessor, this.sendMessageExecutor);
        this.remotingServer.registerProcessor(RequestCode.SEND_MESSAGE_V2, sendProcessor, this.sendMessageExecutor);
        this.remotingServer.registerProcessor(RequestCode.SEND_BATCH_MESSAGE, sendProcessor, this.sendMessageExecutor);
        this.remotingServer.registerProcessor(RequestCode.CONSUMER_SEND_MSG_BACK, sendProcessor, this.sendMessageExecutor);
        this.fastRemotingServer.registerProcessor(RequestCode.SEND_MESSAGE, sendProcessor, this.sendMessageExecutor);
        this.fastRemotingServer.registerProcessor(RequestCode.SEND_MESSAGE_V2, sendProcessor, this.sendMessageExecutor);
        this.fastRemotingServer.registerProcessor(RequestCode.SEND_BATCH_MESSAGE, sendProcessor, this.sendMessageExecutor);
        this.fastRemotingServer.registerProcessor(RequestCode.CONSUMER_SEND_MSG_BACK, sendProcessor, this.sendMessageExecutor);
}

2. 消息處理器處理髮送者發送過來的消息

public class SendMessageProcessor extends AbstractSendMessageProcessor implements NettyRequestProcessor {

    @Override
    public RemotingCommand proce***equest(ChannelHandlerContext ctx,
        RemotingCommand request) throws RemotingCommandException {
        SendMessageContext mqtraceContext;
                ...
        switch (request.getCode()) {
            response = this.sendMessage(ctx, request, mqtraceContext, requestHeader);
        }
    }
}       

繼續看sendMessage..

private RemotingCommand sendMessage(final ChannelHandlerContext ctx,
        ...
        PutMessageResult putMessageResult = this.brokerController.getMessageStore().putMessage(msgInner);
}               

調用MessageStore.putMessage(msgInner)