ElasticSearch 源码之Guice

超、凢脫俗 2022-03-09 06:58 195阅读 0赞

es 使用google开源的依赖注入框架guice，这个项目号称比spring快100倍，不过由于其代码比较简洁，这样的结论是很有可能的。es 是直接把guice的源码放到自己的包内（es把很多开源项目的代码都直接集成到自己项目中，省得依赖一堆的jar包，也使es的jar包达到差不多10M），它位于 org.elasticsearch.common.inject 目录下。

es 里面的组件基本都实现了模块化管理，对guice进行了简单的封装，通过 ModulesBuilder 类构建es的模块，一个es节点模块有：

//源自org.elasticsearch.common.inject;
    public class ModulesBuilder implements Iterable<Module> {
        private final List<Module> modules = new ArrayList<>();
        public ModulesBuilder add(Module... newModules) {
            Collections.addAll(modules, newModules);
            return this;
        }
        @Override
        public Iterator<Module> iterator() {
            return modules.iterator();
        }
        public Injector createInjector() {
            Injector injector = Guice.createInjector(modules);
            ((InjectorImpl) injector).clearCache();
            // in ES, we always create all instances as if they are eager singletons
            // this allows for considerable memory savings (no need to store construction info) as well as cycles
            ((InjectorImpl) injector).readOnlyAllSingletons();
            return injector;
        }
    }
    //通过下面伪代码进行模块化
    ModulesBuilder modules = new ModulesBuilder();
    modules.add(new ToolModule());
    modules.add(new HumanModule());
    Injector injector = modules.createInjector(); // 注入所有module下的实例
    Person instance = injector.getInstance(Person.class);

*  PluginsModule：插件模块
 *  SettingsModule：设置参数模块
 *  NodeModule：节点模块
 *  NetworkModule：网络模块
 *  NodeCacheModule：缓存模块
 *  ScriptModule：脚本模块
 *  JmxModule：jmx模块
 *  EnvironmentModule：环境模块
 *  NodeEnvironmentModule：节点环境模块
 *  ClusterNameModule：集群名模块
 *  ThreadPoolModule：线程池模块
 *  DiscoveryModule：自动发现模块
 *  ClusterModule：集群模块
 *  RestModule：rest模块
 *  TransportModule：tcp模块
 *  HttpServerModule：http模块
 *  IndicesModule：索引模块
 *  SearchModule：搜索模块
 *  ActionModule：行为模块
 *  MonitorModule：监控模块
 *  GatewayModule：持久化模块
 *  NodeClientModule：客户端模块

下面就**TransportModule**的 TransportClient 初始化情况展开说明：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2l0c29mdGNoZW5mZWk_size_16_color_FFFFFF_t_70][]

public TransportClient build() {
            Settings settings = InternalSettingsPreparer.prepareSettings(this.settings);
            settings = settingsBuilder()
                    .put(NettyTransport.PING_SCHEDULE, "5s") // enable by default the transport schedule ping interval
                    .put(settings)
                    .put("network.server", false)
                    .put("node.client", true)
                    .put(CLIENT_TYPE_SETTING, CLIENT_TYPE)
                    .build();
    
            PluginsService pluginsService = new PluginsService(settings, null, null, pluginClasses);
            this.settings = pluginsService.updatedSettings();
    
            Version version = Version.CURRENT;
    
            final ThreadPool threadPool = new ThreadPool(settings);
            NamedWriteableRegistry namedWriteableRegistry = new NamedWriteableRegistry();
    
            boolean success = false;
            try {
                ModulesBuilder modules = new ModulesBuilder();
                modules.add(new Version.Module(version));
                // plugin modules must be added here, before others or we can get crazy injection errors...
                for (Module pluginModule : pluginsService.nodeModules()) {
                    modules.add(pluginModule);
                }
                modules.add(new PluginsModule(pluginsService));
                modules.add(new SettingsModule(this.settings));
                modules.add(new NetworkModule(namedWriteableRegistry));
                modules.add(new ClusterNameModule(this.settings));
                modules.add(new ThreadPoolModule(threadPool));
                modules.add(new TransportModule(this.settings, namedWriteableRegistry));
                modules.add(new SearchModule() {
                    @Override
                    protected void configure() {
                        // noop
                    }
                });
                modules.add(new ActionModule(true));
                modules.add(new ClientTransportModule(hostFailedListener));
                modules.add(new CircuitBreakerModule(this.settings));
    
                pluginsService.processModules(modules);
    
                Injector injector = modules.createInjector();
                final TransportService transportService = injector.getInstance(TransportService.class);
                transportService.start();
                transportService.acceptIncomingRequests();
    
                TransportClient transportClient = new TransportClient(injector); // 初始化TransportClient对象
                success = true;
                return transportClient;
            } finally {
                if (!success) {
                    ThreadPool.terminate(threadPool, 10, TimeUnit.SECONDS);
                }
            }
        }
    //settings模块，源自org.elasticsearch.common.settings
    public class SettingsModule implements Module {
        public SettingsModule(Settings settings, Setting<?>... additionalSettings) {
            this(settings, Arrays.asList(additionalSettings), Collections.emptyList());
        }
        @Override
        public void configure(Binder binder) {
            binder.bind(Settings.class).toInstance(settings);
            binder.bind(SettingsFilter.class).toInstance(settingsFilter);
            binder.bind(ClusterSettings.class).toInstance(clusterSettings);
            binder.bind(IndexScopedSettings.class).toInstance(indexScopedSettings);
        }
    }

看到了吧，es的模块化的解决方案主要是依靠Guice，而优秀的java的模块化解决方案也是我们值得学习与借鉴的。![85017347][]

**引用资料**

[IBM 通过 Guice 进行依赖项注入][IBM_ Guice]

[guice-github-wiki][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2l0c29mdGNoZW5mZWk_size_16_color_FFFFFF_t_70]: /images/20220309/2c93f6c7dcfa49fa9d66a9f7b65e1786.png
[85017347]: /images/20220309/b576abc65005407ea2106c5ab9af0a06.png
[IBM_ Guice]: https://www.ibm.com/developerworks/cn/java/j-guice.html
[guice-github-wiki]: https://github.com/google/guice/wiki/GettingStarted