Elasticsearch源码分析-架构设计之Action
2019-04-01 本文已影响0人
尹亮_36cd
1 请求URL 与对应Action
如果我们发送如下的http请求，elasticsearch是如何匹配对应Action的呢？
curl -XGET 'http://elasticsearch_ip:port/xxx/url/path' -d '{
"请求的content"
}'
在org.elasticsearch.rest.action包下面，存放了处理各种请求的rest action类
在每个action的构造方法中，会将当前action对象注册到指定的url上
public class RestXxxAction extends BaseRestHandler {
@Inject
public RestXxxAction(Settings settings, RestController controller, Client client) {
super(settings, controller, client);
controller.registerHandler(GET, "/xxx/url/path", this);
controller.registerHandler(POST, "/xxx/url/path", this);
}
}
在registerHandler()方法中，会将url path和对应handler添加到http method对象上
public class RestController extends AbstractLifecycleComponent<RestController> {
public void registerHandler(RestRequest.Method method, String path, RestHandler handler) {
switch (method) {
case GET:
getHandlers.insert(path, handler);
break;
case DELETE:
deleteHandlers.insert(path, handler);
break;
case POST:
postHandlers.insert(path, handler);
break;
case PUT:
putHandlers.insert(path, handler);
break;
case OPTIONS:
optionsHandlers.insert(path, handler);
break;
case HEAD:
headHandlers.insert(path, handler);
break;
default:
throw new ElasticsearchIllegalArgumentException("Can't handle [" + method + "] for path [" + path + "]");
}
}
}
elasticsearch使用HttpRequestHandler接收http请求消息，最终会在executeHandler()方法中调用getHandler()方法获取path对应的handler
public class RestController extends AbstractLifecycleComponent<RestController> {
void executeHandler(RestRequest request, RestChannel channel) throws Exception {
final RestHandler handler = getHandler(request);
if (handler != null) {
handler.handleRequest(request, channel);
} else {
if (request.method() == RestRequest.Method.OPTIONS) {
channel.sendResponse(new BytesRestResponse(OK));
} else {
channel.sendResponse(new BytesRestResponse(BAD_REQUEST,
"No handler found for uri [" + request.uri() + "] and method [" + request.method() + "]"));
}
}
}
}
在getHandler()方法中，主要是根据method和path获取在RestXxxAction中添加的handler
public class RestController extends AbstractLifecycleComponent<RestController> {
private RestHandler getHandler(RestRequest request) {
String path = getPath(request);
RestRequest.Method method = request.method();
if (method == RestRequest.Method.GET) {
return getHandlers.retrieve(path, request.params());
} else if (method == RestRequest.Method.POST) {
return postHandlers.retrieve(path, request.params());
} else if (method == RestRequest.Method.PUT) {
return putHandlers.retrieve(path, request.params());
} else if (method == RestRequest.Method.DELETE) {
return deleteHandlers.retrieve(path, request.params());
} else if (method == RestRequest.Method.HEAD) {
return headHandlers.retrieve(path, request.params());
} else if (method == RestRequest.Method.OPTIONS) {
return optionsHandlers.retrieve(path, request.params());
} else {
return null;
}
}
}
elasticsearch在path对应获取Handler后，就执行该handler的handleRequest()方法，作为rest逻辑入口
2 Action与对应TransportAction
在ActionModule中，会将Action和对应的TransportAction注册到actions对象中
public class ActionModule extends AbstractModule {
@Override
protected void configure() {
registerAction(XxxAction.INSTANCE, TransportXxxAction.class);
}
public <Request extends ActionRequest, Response extends ActionResponse> void registerAction(
GenericAction<Request,
Response> action, Class<? extends TransportAction<Request, Response>> transportAction,
Class... supportTransportActions) {
actions.put(action.name(), new ActionEntry<>(action, transportAction, supportTransportActions));
}
}
在RestXxxAction中，最终会调用AbstractClient的xxx方法，并传入Action参数为XxxAction.INSTANCE，即为在ActionModule中注册的Action类
public abstract class AbstractClient implements Client {
@Override
public void xxx(final SuggestRequest request, final ActionListener<SuggestResponse> listener) {
execute(XxxAction.INSTANCE, request, listener);
}
}
在NodeClient中会根据传入的Action参数从actions获取在ActionModule中注册的TransportAction，并执行其execute()方法
public class NodeClient extends AbstractClient {
@Override
public <Request extends ActionRequest, Response extends ActionResponse, RequestBuilder extends ActionRequestBuilder<Request, Response, RequestBuilder, Client>> void execute(Action<Request, Response, RequestBuilder, Client> action, Request request, ActionListener<Response> listener) {
headers.applyTo(request);
TransportAction<Request, Response> transportAction = actions.get((ClientAction)action);
transportAction.execute(request, listener);
}
}
在TransportAction类图个execute()方法中可以看出：
① TransportXxxAction都继承自TransportAction类
② TransportAction的execute()方法仅调用了doExecute()方法
④ TransportXxxAction重写了TransportAction的doExecute()方法
因此，在最终的对应关系为在ActionModule中注册的Action调用的为TransportXxxAction的doExecute()方法
TransportAction类图
TransportAction的execute()方法仅调用了需要子类重写的抽象方法doExecute()
public abstract class TransportAction<Request extends ActionRequest, Response extends ActionResponse> extends AbstractComponent {
protected abstract void doExecute(Request request, ActionListener<Response> listener);
public final void execute(Request request, ActionListener<Response> listener) {
// ...
if (filters.length == 0) {
try {
// TransportAction 子类都要重写这个方法
doExecute(request, listener);
} catch(Throwable t) {
logger.trace("Error during transport action execution.", t);
listener.onFailure(t);
}
} else {
RequestFilterChain requestFilterChain = new RequestFilterChain<>(this, logger);
requestFilterChain.proceed(actionName, request, listener);
}
}
}
3 节点间用Action匹配Handler
如果elasticsearch要请求的节点不是当前节点，则需要将请求发送到对应的节点上执行
在TransportXxxAction中会将ACTION和对应的Handler注册到对应的serverHandlers对象中，在使用transportService发送请求后，MessageChannelHandler.messageReceived()会接受到信息，然后在handleRequest()方法中获取注册的Handler，执行其messageReceived()方法或者交给线程池处理
public class TransportXxxAction {
private final TransportService transportService;
private final SearchService searchService;
@Inject
public TransportXxxAction(Settings settings,
ThreadPool threadPool,
TransportService transportService,
ClusterService clusterService,
XxxService xxxService) {
this.transportService = transportService;
transportService.registerHandler(XXX_ACTION_NAME, new XxxTransportHandler());
this.xxxService= xxxService;
}
public void executeXxx(DiscoveryNode node, final XxxTransportRequest request, final XxxListener listener) {
// 如果shard所在的节点id和当前节点id相同
if (clusterService.state().nodes().localNodeId().equals(node.id())) {
// 当前节点执行逻辑
XxxService.execute(request);
} else {
// shard 所在节点不是当前节点, 发送请求执行远程节点搜索
// node是要发送的节点
transportService.sendRequest(node, XXX_ACTION_NAME, request, new BaseTransportResponseHandler() {
@Override
public QueryXxxResult newInstance() {
return new QueryXxxResult();
}
@Override
public void handleResponse(XxxProvider response) {
listener.onResult(response);
}
@Override
public void handleException(TransportException exp) {
listener.onFailure(exp);
}
@Override
public String executor() {
return ThreadPool.Names.SAME;
}
});
}
}
private class XxxTransportHandler extends BaseTransportRequestHandler {
/**
* 接收远程端口的tcp 请求, 执行Xxx 逻辑
* @param request TransportRequest
* @param channel TransportChannel
* @throws Exception Exception
*/
@Override
public void messageReceived(TransportRequest request, TransportChannel channel) throws Exception {
// 远程节点待执行逻辑
XxxProvider result = XxxService.execute(request);
// 将Query结果响应发送给调用节点
channel.sendResponse(result);
}
@Override
public String executor() {
return ThreadPool.Names.Xxx;
}
}
}
在transportServiceAdapter.handler()方法中，即根据注册的action获取对应的TransportHandler，如果executor是same则执行handler的messageReceived()方法，否则交给线程池执行
public class MessageChannelHandler extends SimpleChannelUpstreamHandler {
protected String handleRequest(Channel channel, StreamInput buffer, long requestId, Version version) throws IOException {
final String action = buffer.readString();
transportServiceAdapter.onRequestReceived(requestId, action);
final NettyTransportChannel transportChannel = new NettyTransportChannel(transport, transportServiceAdapter, action, channel, requestId, version, profileName);
try {
final TransportRequestHandler handler = transportServiceAdapter.handler(action, version);
if (handler == null) {
throw new ActionNotFoundTransportException(action);
}
final TransportRequest request = handler.newInstance();
request.remoteAddress(new InetSocketTransportAddress((InetSocketAddress) channel.getRemoteAddress()));
request.readFrom(buffer);
if (ThreadPool.Names.SAME.equals(handler.executor())) {
//noinspection unchecked
handler.messageReceived(request, transportChannel);
} else {
threadPool.executor(handler.executor()).execute(new RequestHandler(handler, request, transportChannel, action));
}
} catch (Throwable e) {
try {
transportChannel.sendResponse(e);
} catch (IOException e1) {
logger.warn("Failed to send error message back to client for action [" + action + "]", e);
logger.warn("Actual Exception", e1);
}
}
return action;
}
}
下面讲另外一种情况，在ActionModule中注册的Action也都会注册到handler中
public class TransportXxxAction extends HandledTransportAction {
@Inject
public TransportXxxAction (Settings settings, ThreadPool threadPool) {
super(settings, XxxAction.NAME, threadPool);
}
在TransportAction类中同样使用transportService.registerHandler()方法注册handler
public abstract class HandledTransportAction<Request extends ActionRequest, Response extends ActionResponse> extends TransportAction<Request,Response>{
protected HandledTransportAction(Settings settings, String actionName, ThreadPool threadPool, TransportService transportService, ActionFilters actionFilters){
super(settings, actionName, threadPool, actionFilters);
transportService.registerHandler(actionName, new TransportHandler() {
@Override
public Request newInstance(){
return newRequestInstance();
}
});
}
}
因此在InternalTransportClient中，主要是回调proxy.execute()
public class InternalTransportClient extends AbstractClient {
@Inject
public InternalTransportClient(
TransportClientNodesService nodesService,
InternalTransportAdminClient,
Map<String, GenericAction> actions,
Headers headers) {
MapBuilder<Action, TransportActionNodeProxy> actionsBuilder = new MapBuilder<>();
for (GenericAction action : actions.values()) {
if (action instanceof Action) {
actionsBuilder.put((Action) action, new TransportActionNodeProxy(settings, action, transportService));
}
}
this.actions = actionsBuilder.immutableMap();
}
@Override
public void execute(final Action action, final Request request, ActionListener listener) {
headers.applyTo(request);
final TransportActionNodeProxy<Request, Response> proxy = actions.get(action);
nodesService.execute(new TransportClientNodesService.NodeListenerCallback<Response>() {
@Override
public void doWithNode(DiscoveryNode node, ActionListener<Response> listener) {
proxy.execute(node, request, listener);
}
}, listener);
}
}
transportService.sendRequest()中的action.name()即为Action的Name参数，已被注册到对应的handler中了
public class TransportActionNodeProxy extends AbstractComponent {
public void execute(DiscoveryNode node,
final Request request,
final ActionListener<Response> listener) {
ActionRequestValidationException validationException = request.validate();
if (validationException != null) {
listener.onFailure(validationException);
return;
}
transportService.sendRequest(node, action.name(),
request, transportOptions,
new BaseTransportResponseHandler<Response>() {
@Override
public Response newInstance() {
return action.newResponse();
}
@Override
public String executor() {
if (request.listenerThreaded()) {
return ThreadPool.Names.LISTENER;
}
return ThreadPool.Names.SAME;
}
@Override
public void handleResponse(Response response) {
listener.onResponse(response);
}
@Override
public void handleException(TransportException exp) {
listener.onFailure(exp);
}
});
}
}
