在ActionModule模块，主要是注册各种es操作，以TransportAction为接口的一系列实现。

ActionModule的注册类

上图有2个非常重要的es action，一个是index索引，另一个是search检索。

IndexAction

取其中的IndexAction来看具体实现TransportIndexAction，一步步调试进去。

TransportIndexAction继承了TransportReplicationAction，而TransportReplicationAction实现了TransportAction的doExecute方法。
所以其调用链如下，中间涉及了transportService的传输request/response等，

1. Node.modules.add(new ActionModule(false));
2. ActionModule.configure().registerAction(IndexAction.INSTANCE, ransportIndexAction.class);
3. TransportIndexAction.doExecute().createIndexAction.execute()，client端的send任务结束，并设置ActionListener监听response
4. TransportReplicationAction.doExecute{new ReroutePhase((ReplicationTask) task, request, listener).run()};
5. TransportReplicationAction.ReroutePhase.doRun().performAction(node, actionName, false);
6. TransportReplicationAction.ReroutePhase.performAction().transportService.sendRequest()
7. TransportService.sendRequest.transport.sendRequest(node, requestId, action, request, options);
8. NettyTransport.sendRequest()
9. NettyTransport.doStart().createServerBootstrap().configureServerChannelPipelineFactory()
10. NettyTransport.ServerChannelPipelineFactory.getPipeline().MessageChannelHandler
11. MessageChannelHandler.messageReceived().handleRequest()
12. MessageChannelHandler.handleRequest().reg.processMessageReceived(request, transportChannel);
13. RequestHandlerRegistry.processMessageReceived().handler.messageReceived(request, channel);
14. TransportReplicationAction.OperationTransportHandler & PrimaryOperationTransportHandler & ReplicaOperationTransportHandler
15. TransportReplicationAction .PrimaryOperationTransportHandler.messageReceived().PrimaryPhase.doRun().shardOperationOnPrimary() -> TransportIndexAction.shardOperationOnPrimary() -> TransportIndexAction.executeIndexRequestOnPrimary() -> executeIndexRequestOnPrimary().operation.execute(indexShard); -> Engine.Index.execute.shard.index(this); -> IndexShard.index().engine().index(index); -> InternalEngine.index().innerIndex(index); -> InternalEngine.innerIndex().indexWriter.addDocuments(index.docs()); or indexWriter.updateDocuments(index.uid(), index.docs());。index/update doc至Lucene
16. InternalEngine.innerIndex().translog.add(new Translog.Index(index)); doc写入到WAL
17. 在步骤15的时候，primary与replica是同时被call的，即，TransportReplicationAction.ReplicaOperationTransportHandler.messageReceived().AsyncReplicaAction.duRun().shardOperationOnReplica() -> TransportIndexAction.shardOperationOnReplica() -> TransportIndexAction.executeIndexRequestOnReplica() -> executeIndexRequestOnReplica().operation.execute(indexShard); -> ...后续流程与Primary的一致。server端index任务结束，返回response到client
18. TransportIndexAction.doExecute().onResponse()。client利用ActionListener监听之前的createIndexAction.execute()的运行情况

es index action的request和response

SearchAction

search的调用方式与上述的index是一致的，本地节点走local，非本地节点走netty，都是通过handler来实现具体类的回调。

1. Node.modules.add(new ActionModule(false));
2. registerAction(SearchAction.INSTANCE, TransportSearchAction.class);
3. TransportSearchAction.doExecute().SearchQueryThenFetchAsyncAction.start()。这里可以是默认Q_T_F或者D_Q_A_F等
4. AbstractSearchAsyncAction.start().performFirstPhase()
5. AbstractSearchAsyncAction.performFirstPhase().sendExecuteFirstPhase()。client端的send任务结束，并设置ActionListener监听response
6. SearchQueryThenFetchAsyncAction.sendExecuteFirstPhase().searchService.sendExecuteQuery(node, request, listener);
7. SearchServiceTransportAction.sendExecuteQuery().transportService.sendRequest()
8. TransportService.sendRequest().sendRequest(node, action, request, TransportRequestOptions.EMPTY, handler);
9. TransportService.sendRequest().transport.sendRequest(node, requestId, action, request, options);
10. NettyTransport.sendRequest()
11. NettyTransport.doStart().createServerBootstrap().configureServerChannelPipelineFactory()
12. NettyTransport.ServerChannelPipelineFactory.getPipeline().MessageChannelHandler
13. MessageChannelHandler.messageReceived().handleRequest()
14. MessageChannelHandler.handleRequest().reg.processMessageReceived(request, transportChannel);
15. RequestHandlerRegistry.processMessageReceived().handler.messageReceived(request, channel);
16. SearchQueryQueryFetchTransportHandler.messageReceived().searchService.executeFetchPhase(request);。首先执行具体的searchService，然后回写response
17. SearchService.executeFetchPhase().queryPhase.execute(context); & fetchPhase.execute(context);
18. SearchQueryQueryFetchTransportHandler.messageReceived().channel.sendResponse(result);
19. NettyTransport.sendResponse().sendResponse().
20. NettyTransportChannel.sendResponse().future.addListener(onResponseSentListener);。回应步骤5的监听

es searchType async action es search action的request和response

RPC回调

RPC调用有LocalTransport和NettyTransport；回调有RequestHandler、MessageChannelHandler等。理清es关于request和response的异步回调，对于后续的模块化衔接会有帮助。

• client/TransportClient的构造函数注入了TransportProxyClient.execute()方法，接着进入TransportClientNodesService来选择这次request的hash到的node，然后根据action选取对应的实现类TransportActionNodeProxy.execute()，其中execute().transportService.sendRequest()最终会调用NettyTransport.sendRequest()方法，对request进行处理（压缩、版本等），最后发送数据到server端。在Netty中通信的处理类是MessageChannelHandler，其中messageReceived方法用来处理消息，根据不同的状态来调用handleRequest或者handleResponse，即该方法是server端接收请求的入口
• server端通过messageReceived接收到message，解析协议，根据action生成不同request和transportXXXAction，进而执行transportXXXAction.execute(Request request, final ActionListener<Response> listener)。server端处理该message后，将response结果（此结果中包含了前面的requestID）发送给client端

Reference

• elasticsearch源码分析之客户端（三）
• elasticsearch源码分析之服务端（四）
• [源码]Elasticsearch源码2(RPC)