Fescar example解析 - TC流程

开篇

 这篇文章主要是梳理TC处理TM发送消息的过程，由于消息种类较多所以打算额外写篇文章分析，这篇文章主要把进入网络层以后的基本流程梳理下，方便大家阅读源码。

 这篇文章的没有针对TM的接收部分进行分析，针对收到报文以后的处理流程。

 Transaction Coordinator (TC)： 事务协调器，维护全局事务的运行状态，负责协调并驱动全局事务的提交或回滚。

TC处理时序图

TC.jpg

说明：

• TC处理流程核心模块是DefaultCoordinator和DefaultCore。
• DefaultCoordinator和DefaultCore的调用方式是直接方法进行调用。

TC处理流程源码分析

public class DefaultCoordinator extends AbstractTCInboundHandler
    implements TransactionMessageHandler, ResourceManagerInbound {

    private ServerMessageSender messageSender;
    private Core core = CoreFactory.get();

    public DefaultCoordinator(ServerMessageSender messageSender) {
        this.messageSender = messageSender;
        core.setResourceManagerInbound(this);
    }

    @Override
    protected void doGlobalBegin(GlobalBeginRequest request, GlobalBeginResponse response, RpcContext rpcContext) 
        throws TransactionException {
        response.setXid(core.begin(rpcContext.getApplicationId(), rpcContext.getTransactionServiceGroup(), 
                                   request.getTransactionName(), request.getTimeout()));
    }

    @Override
    protected void doGlobalCommit(GlobalCommitRequest request, GlobalCommitResponse response, RpcContext rpcContext) 
        throws TransactionException {
        response.setGlobalStatus(core.commit(XID.generateXID(request.getTransactionId())));

    }

    @Override
    protected void doGlobalRollback(GlobalRollbackRequest request, GlobalRollbackResponse response, RpcContext rpcContext) 
        throws TransactionException {
        response.setGlobalStatus(core.rollback(XID.generateXID(request.getTransactionId())));

    }

    @Override
    protected void doGlobalStatus(GlobalStatusRequest request, GlobalStatusResponse response, RpcContext rpcContext) 
        throws TransactionException {
        response.setGlobalStatus(core.getStatus(XID.generateXID(request.getTransactionId())));
    }
}

说明：

• DefaultCoordinator提供doGlobalBegin实现事务的开启。

• DefaultCoordinator提供doGlobalCommit实现事务的提交。

• DefaultCoordinator提供doGlobalRollback实现事务的回滚。

• DefaultCoordinator的Core通过CoreFactory方法获取。

public class CoreFactory {

    private static class SingletonHolder {
        private static Core INSTANCE = new DefaultCore();
    }

    public static final Core get() {
        return CoreFactory.SingletonHolder.INSTANCE;
    }

    public static void set(Core core) {
        CoreFactory.SingletonHolder.INSTANCE = core;
    }
}

说明：

• CoreFactory提供获取DefaultCore的方法。

public class DefaultCore implements Core {

    private LockManager lockManager = LockManagerFactory.get();
    private ResourceManagerInbound resourceManagerInbound;

    public String begin(String applicationId, String transactionServiceGroup, String name, int timeout) 
    throws TransactionException {}

    @Override
    public GlobalStatus commit(String xid) throws TransactionException {}

    @Override
    public void doGlobalCommit(GlobalSession globalSession, boolean retrying) throws TransactionException {}

    private void asyncCommit(GlobalSession globalSession) throws TransactionException {}

    private void queueToRetryCommit(GlobalSession globalSession) throws TransactionException {}

    private void queueToRetryRollback(GlobalSession globalSession) throws TransactionException {}

    @Override
    public GlobalStatus rollback(String xid) throws TransactionException {}

    @Override
    public void doGlobalRollback(GlobalSession globalSession, boolean retrying) throws TransactionException {}
}

说明：

• DefaultCore 是TC执行事务操作的核心。

• DefaultCore 提供begin/commit/rollback等操作。