Seata的服務端啓動過程分析

下載Seata服務端源代碼

這樣用的是Seata的最新版本V1.0

解壓源代碼文件， 導入源代碼到IDEA當中

Seata服務端源代碼是一個標準的Maven工程，很容易很入到IDEA工具當中，最後源代碼工程文件目錄如下：

查看Seata的啓動腳本

#!/bin/sh
# resolve links - $0 may be a softlink
PRG="$0"

while [ -h "$PRG" ]; do
  ls=`ls -ld "$PRG"`
  link=`expr "$ls" : '.*-> \(.*\)$'`
  if expr "$link" : '/.*' > /dev/null; then
    PRG="$link"
  else
    PRG=`dirname "$PRG"`/"$link"
  fi
done
PRGDIR=`dirname "$PRG"`
BASEDIR=`cd "$PRGDIR/.." >/dev/null; pwd`
# Reset the REPO variable. If you need to influence this use the environment setup file.
REPO=
# OS specific support.  $var _must_ be set to either true or false.
cygwin=false;
darwin=false;
case "`uname`" in
  CYGWIN*) cygwin=true ;;
  Darwin*) darwin=true
           if [ -z "$JAVA_VERSION" ] ; then
             JAVA_VERSION="CurrentJDK"
           else
             echo "Using Java version: $JAVA_VERSION"
           fi
                   if [ -z "$JAVA_HOME" ]; then
                      if [ -x "/usr/libexec/java_home" ]; then
                              JAVA_HOME=`/usr/libexec/java_home`
                          else
                              JAVA_HOME=/System/Library/Frameworks/JavaVM.framework/Versions/${JAVA_VERSION}/Home
                          fi
           fi       
           ;;
esac

if [ -z "$JAVA_HOME" ] ; then
  if [ -r /etc/gentoo-release ] ; then
    JAVA_HOME=`java-config --jre-home`
  fi
fi

# For Cygwin, ensure paths are in UNIX format before anything is touched
if $cygwin ; then
  [ -n "$JAVA_HOME" ] && JAVA_HOME=`cygpath --unix "$JAVA_HOME"`
  [ -n "$CLASSPATH" ] && CLASSPATH=`cygpath --path --unix "$CLASSPATH"`
fi

# If a specific java binary isn't specified search for the standard 'java' binary
if [ -z "$JAVACMD" ] ; then
  if [ -n "$JAVA_HOME"  ] ; then
    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
      # IBM's JDK on AIX uses strange locations for the executables
      JAVACMD="$JAVA_HOME/jre/sh/java"
    else
      JAVACMD="$JAVA_HOME/bin/java"
    fi
  else
    JAVACMD=`which java`
  fi
fi

if [ ! -x "$JAVACMD" ] ; then
  echo "Error: JAVA_HOME is not defined correctly." 1>&2
  echo "  We cannot execute $JAVACMD" 1>&2
  exit 1
fi

if [ -z "$REPO" ]
then
  REPO="$BASEDIR"/lib
fi

CLASSPATH="$BASEDIR"/conf:"$REPO"/*

ENDORSED_DIR=
if [ -n "$ENDORSED_DIR" ] ; then
  CLASSPATH=$BASEDIR/$ENDORSED_DIR/*:$CLASSPATH
fi

if [ -n "$CLASSPATH_PREFIX" ] ; then
  CLASSPATH=$CLASSPATH_PREFIX:$CLASSPATH
fi

# For Cygwin, switch paths to Windows format before running java
if $cygwin; then
  [ -n "$CLASSPATH" ] && CLASSPATH=`cygpath --path --windows "$CLASSPATH"`
  [ -n "$JAVA_HOME" ] && JAVA_HOME=`cygpath --path --windows "$JAVA_HOME"`
  [ -n "$HOME" ] && HOME=`cygpath --path --windows "$HOME"`
  [ -n "$BASEDIR" ] && BASEDIR=`cygpath --path --windows "$BASEDIR"`
  [ -n "$REPO" ] && REPO=`cygpath --path --windows "$REPO"`
fi

exec "$JAVACMD" $JAVA_OPTS -server -Xmx2048m -Xms2048m -Xmn1024m -Xss512k -XX:SurvivorRatio=10 -XX:MetaspaceSize=128m -XX:MaxMetaspaceSize=256m -XX:MaxDirectMemorySize=1024m -XX:-OmitStackTraceInFastThrow -XX:-UseAdaptiveSizePolicy -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath="$BASEDIR"/logs/java_heapdump.hprof -XX:+DisableExplicitGC -XX:+CMSParallelRemarkEnabled -XX:+UseCMSInitiatingOccupancyOnly -XX:CMSInitiatingOccupancyFraction=75 -Xloggc:"$BASEDIR"/logs/seata_gc.log -verbose:gc -Dio.netty.leakDetectionLevel=advanced \
  -classpath "$CLASSPATH" \
  -Dapp.name="seata-server" \
  -Dapp.pid="$$" \
  -Dapp.repo="$REPO" \
  -Dapp.home="$BASEDIR" \
  -Dbasedir="$BASEDIR" \
  io.seata.server.Server \
  "$@"

啓動腳本分析

從腳本當中可以看到啓動的類入口爲io.seata.server.Server,從源代碼當中可以明顯的看出Seata的底層通信框架使用的是Netty

Seata服務端啓動類

/**
 * The type Server.
 * 服務器端啓動
 * @author slievrly
 */
public class Server {

    private static final Logger LOGGER = LoggerFactory.getLogger(Server.class);
    private static final int MIN_SERVER_POOL_SIZE = 100;
    private static final int MAX_SERVER_POOL_SIZE = 500;
    private static final int MAX_TASK_QUEUE_SIZE = 20000;
    private static final int KEEP_ALIVE_TIME = 500;
    private static final ThreadPoolExecutor WORKING_THREADS = new ThreadPoolExecutor(
        MIN_SERVER_POOL_SIZE,
        MAX_SERVER_POOL_SIZE,
        KEEP_ALIVE_TIME,
        TimeUnit.SECONDS,
        new LinkedBlockingQueue<>(MAX_TASK_QUEUE_SIZE),//阻塞隊列
        new NamedThreadFactory("ServerHandlerThread", MAX_SERVER_POOL_SIZE),
        new ThreadPoolExecutor.CallerRunsPolicy());

    /**
     * 整個seata服務的入口應用
     */
    public static void main(String[] args) throws IOException {
        //獲取所有傳的參數
        ParameterParser parameterParser = new ParameterParser(args);

        //初始化監聽指標組件
        MetricsManager.get().init();

        System.setProperty(ConfigurationKeys.STORE_MODE, parameterParser.getStoreMode());

        RpcServer rpcServer = new RpcServer(WORKING_THREADS);
        //server port
        rpcServer.setListenPort(parameterParser.getPort());
        UUIDGenerator.init(parameterParser.getServerNode());
        //log store mode : file, db
        SessionHolder.init(parameterParser.getStoreMode());
        DefaultCoordinator coordinator = new DefaultCoordinator(rpcServer);
        coordinator.init();
        rpcServer.setHandler(coordinator);
        //註冊關閉註銷執行方法
        ShutdownHook.getInstance().addDisposable(coordinator);
        //127.0.0.1 and 0.0.0.0 are not valid here.
        if (NetUtil.isValidIp(parameterParser.getHost(), false)) {
            XID.setIpAddress(parameterParser.getHost());
        } else {
            XID.setIpAddress(NetUtil.getLocalIp());
        }
        XID.setPort(rpcServer.getListenPort());
        try {
            //服務端啓動
            rpcServer.init();
        } catch (Throwable e) {
            LOGGER.error("rpcServer init error:{}", e.getMessage(), e);
            System.exit(-1);
        }
        System.exit(0);
    }
}

RpcServer#init方法

 /**
     * Init.
     * 服務端啓動接口
     */
    @Override
    public void init() {
        super.init();
        setChannelHandlers(RpcServer.this);
        DefaultServerMessageListenerImpl defaultServerMessageListenerImpl = new DefaultServerMessageListenerImpl(
            transactionMessageHandler);
        defaultServerMessageListenerImpl.init();
        defaultServerMessageListenerImpl.setServerMessageSender(this);
        //進行監聽客戶發佈的消息
        this.setServerMessageListener(defaultServerMessageListenerImpl);
        //開啓服務端
        super.start();
    }

使用IDEA啓動Seata 服務端，會出現如下問題
io.seata.codec.protobuf.generated不存在，導致seata server啓動不了？

出現這個問題是protobuf協議自動生成的代碼在0.8.1已經移除。
可以通過如下的方式臨時啓動Seata Server代碼

        <dependency>
            <groupId>${project.groupId}</groupId>
            <artifactId>seata-codec-all</artifactId>
            <version>${project.version}</version>
            <exclusions>
                <exclusion>
                    <groupId>${project.groupId}</groupId>
                    <artifactId>seata-codec-protobuf</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

這樣子就可以啓動功能了，其他內容後面補充