Cassandra源码解析系列启动模块

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Cassandra源码解析系列启动模块

玄陵 2020-03-23 11:31:31 浏览479
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以3.11.4为基础

Cassandra 启动流程从bin下面的cassandra脚本开始进去看,会涉及到cassandra-env.sh进行进程启动的一些参数设置比如堆上内存分配,日志参数配置,基本环境设置等,我们直接看到启动的进程,也就是launch_service 这个函数,然后看到里面的exec 执行JAVA的进程,也就是class(launch_service参数传进来的classname为org.apache.cassandra.service.CassandraDaemon类);大概的流程是:

cassandra -> lauch_service -> JAVA启动org.apache.cassandra.service.CassandraDaemon;

接下来就是看到org.apache.cassandra.service.CassandraDaemon这个类,直接在这个类里面通过main函数找到启动的入口:

  public static void main(String[] args)
    {
        instance.activate();
    }
    

在active函数里面有3个主要要看的函数:

        // Do not put any references to DatabaseDescriptor above the forceStaticInitialization call.
        try
        {
            applyConfig();

            MBeanWrapper.instance.registerMBean(new StandardMBean(new NativeAccess(), NativeAccessMBean.class), MBEAN_NAME, MBeanWrapper.OnException.LOG);

            if (FBUtilities.isWindows)
            {
                // We need to adjust the system timer on windows from the default 15ms down to the minimum of 1ms as this
                // impacts timer intervals, thread scheduling, driver interrupts, etc.
                WindowsTimer.startTimerPeriod(DatabaseDescriptor.getWindowsTimerInterval());
            }

            setup();

            String pidFile = System.getProperty("cassandra-pidfile");

            if (pidFile != null)
            {
                new File(pidFile).deleteOnExit();
            }

            start();

        }
        catch (Throwable e)
        {
            boolean logStackTrace =
            e instanceof ConfigurationException ? ((ConfigurationException)e).logStackTrace : true;

            System.out.println("Exception (" + e.getClass().getName() + ") encountered during startup: " + e.getMessage());

            if (logStackTrace)
            {
                if (runManaged)
                    logger.error("Exception encountered during startup", e);
                // try to warn user on stdout too, if we haven't already detached
                e.printStackTrace();
                exitOrFail(3, "Exception encountered during startup", e);
            }
            else
            {
                if (runManaged)
                    logger.error("Exception encountered during startup: {}", e.getMessage());
                // try to warn user on stdout too, if we haven't already detached
                System.err.println(e.getMessage());
                exitOrFail(3, "Exception encountered during startup: " + e.getMessage());
            }
        }
    

applyConfig();主要是用来初始化cassandra.yaml配置文件里的基本的配置,setup主要是做一些单节点初始化的时候的一些初始化工作,比如load本地的sstable元信息到内存,清除无用的sstable文件,启动的时候没有commit的transaction 执行或回滚,commitlog 的启动以及回放,集群元信息的效验,启动compaction,启动7000端口内部交流server等等事情;

start函数主要是启动9042的client监听端口,主要是netty的server,当然如果是thrift的话,也启动9160 端口服务;

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