Elasticsearch 通信模块的分析

2020-05-22 00:00:00 函数 线程 节点 请求 回调

Elasticsearch是一个基于Lucene的分布式实时搜索框架，它本身能够接受用户发来的http 请求， 集群节点之间也会有相关的通信。

通信模块的简介

Elasticsearch 中的通信相关的配置都是由NetworkModule 这个类完成的。 NetworkModule 里面的配置主要分三大部分:

  1. HttpServerTransport: 这个主要负责接受用户发来的请求，然后分发请求
  2. Transport: 这个主要负责集群间的通信，应该是Elasticsearch 的RPC
  3. TransportInterceptor 是对连接之间的拦截，在连接发送之前 或是接到之后先做一些相关处理，这个在Elasticseach 使用的并不多，目前只是提供了这功能的接口，可以让之后更容扩展.

由于3在Elasticseach 使用的并不多，我在这里面不多讲，主要讲1 和2

Elasticsearch是一个非常扩展性非常强的系统，每个功能都模块化，服务化。而且它提供了插件(Plugin)的接口，让每一个功能都很容易可以扩展，实现了可插拔。对于网络相关的的插件是NetworkPlugin

NetworkPlugin 提供了三个函数来分别获得和配置HttpServerTransport, Transport, TransportInterceptor.

public interface NetworkPlugin {

    /**
     * Returns a list of {@link TransportInterceptor} instances that are used to intercept incoming and outgoing
     * transport (inter-node) requests. This must not return <code>null</code>
     *
     * @param namedWriteableRegistry registry of all named writeables registered
     * @param threadContext a {@link ThreadContext} of the current nodes or clients {@link ThreadPool} that can be used to set additional
     *                      headers in the interceptors
     */
    default List<TransportInterceptor> getTransportInterceptors(NamedWriteableRegistry namedWriteableRegistry,
                                                                ThreadContext threadContext) {
        return Collections.emptyList();
    }

    /**
     * Returns a map of {@link Transport} suppliers.
     * See {@link org.elasticsearch.common.network.NetworkModule#TRANSPORT_TYPE_KEY} to configure a specific implementation.
     */
    default Map<String, Supplier<Transport>> getTransports(Settings settings, ThreadPool threadPool, BigArrays bigArrays,
                                                           PageCacheRecycler pageCacheRecycler,
                                                           CircuitBreakerService circuitBreakerService,
                                                           NamedWriteableRegistry namedWriteableRegistry,
                                                           NetworkService networkService) {
        return Collections.emptyMap();
    }

    /**
     * Returns a map of {@link HttpServerTransport} suppliers.
     * See {@link org.elasticsearch.common.network.NetworkModule#HTTP_TYPE_SETTING} to configure a specific implementation.
     */
    default Map<String, Supplier<HttpServerTransport>> getHttpTransports(Settings settings, ThreadPool threadPool, BigArrays bigArrays,
                                                                         CircuitBreakerService circuitBreakerService,
                                                                         NamedWriteableRegistry namedWriteableRegistry,
                                                                         NamedXContentRegistry xContentRegistry,
                                                                         NetworkService networkService,
                                                                         HttpServerTransport.Dispatcher dispatcher) {
        return Collections.emptyMap();
    }
}

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