解析S4中node的启动原理（二）——s4Node源码分析

S4Node源码分析

上一篇我们谈到Tools包含了S4中的所有命令，而启动一个Node就是调用S4Node这个类。S4Node 的任务是将收到的参数进行解析，得到S4NodeArgs中参数相应的值。

 public static class S4NodeArgs {

        @Parameter(names = { "-c", "-cluster" }, description = "Cluster name", required = true)
        String clusterName = null;

        @Parameter(names = "-baseConfig", description = "S4 base configuration file", required = false)
        String baseConfigFilePath = null;

        @Parameter(names = "-zk", description = "Zookeeper connection string", required = false)
        String zkConnectionString = "localhost:2181";

        @Parameter(names = { "-namedStringParameters", "-p" }, description = "Comma-separated list of "
                + "inline configuration parameters, taking precedence over homonymous configuration parameters from "
                + "configuration files. Syntax: '-p=name1=value1,name2=value2 '. "
                + "NOTE: application parameters should be injected in the application configuration/deployment step."
                + "Only parameters relevant to the node should be injected here, e.g. metrics logging configuration", hidden = false, converter = ParsingUtils.InlineConfigParameterConverter.class)
        List<String> extraNamedParameters = new ArrayList<String>();
    }

  以得到的值为参数，调用startNode（S4NodeArgs nodeArgs）方法，该方法构造一个Guice的ingector，主要是将命令行的参数以及incubator-s4-master\incubator-s4-master\subprojects\s4-base\src\main\resources中的default.s4.base.properties中的变量注入到S4Bootstrap类中，然后调用S4Bootstrap的start（）方法。S4Bootstrap类是S4Node的真正启动程序。

private static void startNode(S4NodeArgs nodeArgs) throws InterruptedException, IOException {
        Thread.setDefaultUncaughtExceptionHandler(new UncaughtExceptionHandler() {

            @Override
            public void uncaughtException(Thread t, Throwable e) {
                logger.error("Uncaught exception in thread {}", t.getName(), e);

            }
        });

        // inject parameter from the command line, including zk string
        Map<String, String> inlineParameters = Maps.newHashMap(ParsingUtils
                .convertListArgsToMap(nodeArgs.extraNamedParameters));
        inlineParameters.put("s4.cluster.zk_address", nodeArgs.zkConnectionString);

        Injector injector = Guice.createInjector(Modules.override(
                new BaseModule(Resources.getResource("default.s4.base.properties").openStream(), nodeArgs.clusterName))
                .with(new ParametersInjectionModule(inlineParameters)));

        S4Bootstrap bootstrap = injector.getInstance(S4Bootstrap.class);
        try {
            bootstrap.start(injector);
        } catch (ArchiveFetchException e1) {
            logger.error("Cannot fetch module dependencies.", e1);
        }
    }

 如果想了解Guice中Injector的构造及其注入原理，可以参考http://www.kurttlin.com/post/s4-def-guide/3。