Elasticsearch6.3.2启动过程源码阅读记录

时间 2019-11-06

标签 elasticsearch6.3.2 elasticsearch 启动过程源码阅读记录栏目日志分析繁體版

原文原文链接

Elasticsearch6.3.2启动过程源码阅读记录

网上有不少关于es的源码分析，以为本身技术深度还不够，因此这些文章只是看源码过程当中的一个笔记，谈不上分析。html

整个启动过程以类名.方法名，按顺序依次描述以下：java

Elasticsearch.main启动入口类，注册JVM关闭钩子用来清理资源。node
Command.mainwithoutErrorHandling 在es正式启动以前，加载一些命令：好比 ./elasticsearch -help命令app

starts elasticsearch
   Option                Description                                               
   ------                -----------                                               
   -E <KeyValuePair>     Configure a setting                                       
   -V, --version         Prints elasticsearch version information and exits        
   -d, --daemonize       Starts Elasticsearch in the background                    
   -h, --help            show help

EnvironmentAwareCommand.execute加载配置参数jvm

putSystemPropertyIfSettingIsMissing(settings, "path.data", "es.path.data");
        putSystemPropertyIfSettingIsMissing(settings, "path.home", "es.path.home");
        putSystemPropertyIfSettingIsMissing(settings, "path.logs", "es.path.logs");

InternalSettingsPrepare.prePareEnvironment解析ElasticSearch.yml中的配置参数elasticsearch

Prepares the settings by gathering all elasticsearch system properties, optionally loading the configuration settings,and then replacing all property placeholders.and then replacing all property placeholders.ide

ElasticSearch.execute执行初始化命令。另外在源码中还有看到一些有趣的注释，好比必须设置java.io.tmpdir，这个参数在 config/jvm.options文件中指定。源码分析

// a misconfigured java.io.tmpdir can cause hard-to-diagnose problems later, so reject it immediately
        try {
            env.validateTmpFile();
        } catch (IOException e) {
            throw new UserException(ExitCodes.CONFIG, e.getMessage());
        }

Bootstrap.init正式开始启动ElasticSearch。This method is invoked by {@link Elasticsearch#main(String[])} to startup elasticsearch。ui

建立节点启动时须要的环境变量参数this

final Environment environment = createEnvironment(foreground, pidFile, keystore, initialEnv.settings(), initialEnv.configFile());

checkLucene()检查匹配的Lucene jar包。

建立节点，在下面Node构造方法中将详细分析这个过程。

node = new Node(environment) {
            @Override
            protected void validateNodeBeforeAcceptingRequests(
                final BootstrapContext context,
                final BoundTransportAddress boundTransportAddress, List<BootstrapCheck> checks) throws NodeValidationException {
                BootstrapChecks.check(context, boundTransportAddress, checks);
            }
        };

Node.java 构造方法 Node(final Environment environment, Collection<Class<? extends Plugin>> classpathPlugins)。在这个构建方法里面，完成了建立一个节点所需的各类信息，这个方法很是重要，下面就例举出几个节点建立过程当中几个重要的流程：

设置节点环境变量信息(A component that holds all data paths for a single node.)

nodeEnvironment = new NodeEnvironment(tmpSettings, environment);

构造插件服务(PluginService)，

this.pluginsService = new PluginsService(tmpSettings, environment.configFile(), environment.modulesFile(), environment.pluginsFile(), classpathPlugins);

看这个构造方法的注释：

/**
     * Constructs a new PluginService
     * @param settings The settings of the system
     * @param modulesDirectory The directory modules exist in, or null if modules should not be loaded from the filesystem
     * @param pluginsDirectory The directory plugins exist in, or null if plugins should not be loaded from the filesystem
     * @param classpathPlugins Plugins that exist in the classpath which should be loaded
     */
    public PluginsService(Settings settings, Path configPath, Path modulesDirectory, Path pluginsDirectory, Collection<Class<? extends Plugin>> classpathPlugins) {

其实就是加载：elasticsearch-6.3.2/modules 和 elasticsearch-6.3.2/plugins两个目录下的内容。

建立自定义的线程池，节点执行各类任务用的吧。

final ThreadPool threadPool = new ThreadPool(settings, executorBuilders.toArray(new ExecutorBuilder[0]));

建立NodeClient，Client that executes actions on the local node。
```
client = new NodeClient(settings, threadPool);
```

AnalysisModule (An internal registry for tokenizer, token filter, char filter and analyzer)各类分词器。

AnalysisModule analysisModule = new AnalysisModule(this.environment, pluginsService.filterPlugins(AnalysisPlugin.class));

SettingsModule(A module that binds the provided settings to the {@link Settings} interface) 各类配置参数用到。好比 jvm.options 和 elasticsearch.yml里面配置的各类参数。
```
final SettingsModule settingsModule = new SettingsModule(this.settings, additionalSettings, additionalSettingsFilter);
```

节点是集群的一份子，确定须要集群相关的服务

final ClusterService clusterService = new ClusterService(settings, settingsModule.getClusterSettings(), threadPool,
               ClusterModule.getClusterStateCustomSuppliers(clusterPlugins));

集群信息相关服务(Interface for a class used to gather information about a cluster at regular intervals) 周期性同步集群状态。
```
final ClusterInfoService clusterInfoService = newClusterInfoService(settings, clusterService, threadPool, client, listener::onNewInfo);
```

建立Module

ModulesBuilder modules = new ModulesBuilder();
// plugin modules must be added here, before others or we can get crazy injection errors...
            for (Module pluginModule : pluginsService.createGuiceModules()) {
                modules.add(pluginModule);
            }

好比：SearchModule(Sets up things that can be done at search time like queries, aggregations, and suggesters)

SearchModule searchModule = new SearchModule(settings, false, pluginsService.filterPlugins(SearchPlugin.class));

还有 ActionModule(Builds and binds the generic action map, all {@link TransportAction}s, and {@link ActionFilters}.)

ActionModule actionModule = new ActionModule(false, settings, clusterModule.getIndexNameExpressionResolver(),
                settingsModule.getIndexScopedSettings(), settingsModule.getClusterSettings(), settingsModule.getSettingsFilter(),
                threadPool, pluginsService.filterPlugins(ActionPlugin.class), client, circuitBreakerService, usageService);
            modules.add(actionModule);

还有 DiscoveryModule(A module for loading classes for node discovery)

final DiscoveryModule discoveryModule = new DiscoveryModule(this.settings, threadPool, transportService, namedWriteableRegistry,
                networkService, clusterService.getMasterService(), clusterService.getClusterApplierService(),
                clusterService.getClusterSettings(), pluginsService.filterPlugins(DiscoveryPlugin.class),
                clusterModule.getAllocationService());

看一下，一共都有哪些module:

最终关联了一大批的Module

modules.add(b -> {
                    b.bind(Node.class).toInstance(this);
                    b.bind(NodeService.class).toInstance(nodeService);
                    b.bind(NamedXContentRegistry.class).toInstance(xContentRegistry);
                    b.bind(PluginsService.class).toInstance(pluginsService);
                    b.bind(Client.class).toInstance(client);
                    b.bind(NodeClient.class).toInstance(client);
                    b.bind(Environment.class).toInstance(this.environment);
                    b.bind(ThreadPool.class).toInstance(threadPool);
                    b.bind(NodeEnvironment.class).toInstance(nodeEnvironment);
                    b.bind(ResourceWatcherService.class).toInstance(resourceWatcherService);
                    b.bind(CircuitBreakerService.class).toInstance(circuitBreakerService);
                    b.bind(BigArrays.class).toInstance(bigArrays);
                    b.bind(ScriptService.class).toInstance(scriptModule.getScriptService());
                    b.bind(AnalysisRegistry.class).toInstance(analysisModule.getAnalysisRegistry());
                    b.bind(IngestService.class).toInstance(ingestService);
                    b.bind(UsageService.class).toInstance(usageService);
                    b.bind(NamedWriteableRegistry.class).toInstance(namedWriteableRegistry);
                    b.bind(MetaDataUpgrader.class).toInstance(metaDataUpgrader);
                    b.bind(MetaStateService.class).toInstance(metaStateService);
                    b.bind(IndicesService.class).toInstance(indicesService);
                    b.bind(SearchService.class).toInstance(searchService);
                    b.bind(SearchTransportService.class).toInstance(searchTransportService);
                    b.bind(SearchPhaseController.class).toInstance(new SearchPhaseController(settings,
                        searchService::createReduceContext));
                    b.bind(Transport.class).toInstance(transport);
                    b.bind(TransportService.class).toInstance(transportService);
                    b.bind(NetworkService.class).toInstance(networkService);
                    b.bind(UpdateHelper.class).toInstance(new UpdateHelper(settings, scriptModule.getScriptService()));
                    b.bind(MetaDataIndexUpgradeService.class).toInstance(metaDataIndexUpgradeService);
                    b.bind(ClusterInfoService.class).toInstance(clusterInfoService);
                    b.bind(GatewayMetaState.class).toInstance(gatewayMetaState);
                    b.bind(Discovery.class).toInstance(discoveryModule.getDiscovery());

总之，Node.java的构造方法里面实现了建立一个ElasticSearch节点所必须的各类信息，想要了解ElasticSearch节点的内部结构，应该就得多看看这个方法里面的代码吧。

ModulesBuilder.createInjector 使用了Guice 依赖注入。
```
injector = modules.createInjector();
```

Node.start，前面建立了节点，如今开始启动节点。(Start the node. If the node is already started, this method is no-op)

先拿到对象实例，再启动

injector.getInstance(MappingUpdatedAction.class).setClient(client);
        injector.getInstance(IndicesService.class).start();
        injector.getInstance(IndicesClusterStateService.class).start();
        injector.getInstance(SnapshotsService.class).start();
        injector.getInstance(SnapshotShardsService.class).start();
        injector.getInstance(RoutingService.class).start();
        injector.getInstance(SearchService.class).start();
        nodeService.getMonitorService().start();
//...
        Discovery discovery = injector.getInstance(Discovery.class);
      clusterService.getMasterService().setClusterStatePublisher(discovery::publish);
        discovery.start(); // start before cluster service so that it can set initial state on ClusterApplierService
        clusterService.start();

里面的每一个方法，都值得花时间去深刻研究下。哈哈。。。

总结

总的来看，Elasticsearch启动过程三大步，第一步：加载各类配置信息，这些配置信息既有自定义的配置信息，也有机器的环境变量信息，它们告诉es，我想要建立一个什么样的节点。第二步：建立节点，节点具备各类各样的功能，好比说执行搜索查询请求、选主、与其余节点同步集群状态信息……这些功能须要各类服务/插件/模块Module来实现。第三步：启动节点，其实就是各类模块、插件、服务的启动。

最后放一张整理上上面的9个方法的调用关系图：

原文：https://www.cnblogs.com/hapjin/p/10124269.html