AgentResource类位于org.apache.ambari.server.agent.rest包下，如下图：
AgentResource类位于Ambari-Server下，它为Ambari-Agent提供API(REST API)，以获取集群配置更改，以及报告在集群节点上运行的服务的节点属性和状态。
源代码如下（添加了部分注释）
package org.apache.ambari.server.agent.rest; import javax.servlet.http.HttpServletRequest; import javax.ws.rs.Consumes; import javax.ws.rs.GET; import javax.ws.rs.POST; import javax.ws.rs.Path; import javax.ws.rs.PathParam; import javax.ws.rs.Produces; import javax.ws.rs.WebApplicationException; import javax.ws.rs.core.Context; import javax.ws.rs.core.MediaType; import org.apache.ambari.server.AmbariException; import org.apache.ambari.server.agent.ComponentsResponse; import org.apache.ambari.server.agent.HeartBeat; import org.apache.ambari.server.agent.HeartBeatHandler; import org.apache.ambari.server.agent.HeartBeatResponse; import org.apache.ambari.server.agent.Register; import org.apache.ambari.server.agent.RegistrationResponse; import org.apache.ambari.server.state.fsm.InvalidStateTransitionException; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import com.google.inject.Inject; import org.apache.ambari.server.agent.RegistrationStatus; /** * Agent Resource represents Ambari agent controller. * 代理资源表示Ambari代理控制器。 * It provides API for Ambari agents to get the cluster configuration changes * as well as report the node attributes and state of services running the on * the cluster nodes * 它为Ambari代理提供API(REST API)，以获取集群配置更改，以及报告在集群节点上运行的服务的节点属性和状态 */ @Path("/") public class AgentResource { private static HeartBeatHandler hh; private static Log LOG = LogFactory.getLog(AgentResource.class); @Inject public static void init(HeartBeatHandler instance) { hh = instance; //hh.start(); } /** * Explicitly start HH * 显式启动HH(HeartBeatHandler) */ public static void statHeartBeatHandler() { hh.start(); } /** * Register information about the host (Internal API to be used for * Ambari Agent) * 注册有关主机的信息（用于Ambari代理的内部API） * * @response.representation.200.doc This API is invoked by Ambari agent running * on a cluster to register with the server. * 此API由集群上运行的Ambari代理调用以向服务器注册 * * @response.representation.200.mediaType application/json * @response.representation.406.doc Error in register message format * @response.representation.408.doc Request Timed out * @param message Register message * @throws InvalidStateTransitionException * @throws AmbariException * @throws Exception */ @Path("register/{hostName}") @POST @Consumes(MediaType.APPLICATION_JSON) @Produces({MediaType.APPLICATION_JSON}) public RegistrationResponse register(Register message, @Context HttpServletRequest req) throws WebApplicationException, InvalidStateTransitionException { /* Call into the heartbeat handler 调用心跳处理程序 */ RegistrationResponse response = null; try { //注册并返回响应 response = hh.handleRegistration(message); LOG.debug("Sending registration response " + response); } catch (AmbariException ex) { response = new RegistrationResponse(); response.setResponseId(-1); response.setResponseStatus(RegistrationStatus.FAILED); response.setExitstatus(1); response.setLog(ex.getMessage()); return response; } return response; } /** * Update state of the node (Internal API to be used by Ambari agent). * 更新节点的状态（Ambari代理使用的内部API）。 * * @response.representation.200.doc This API is invoked by Ambari agent running * on a cluster to update the state of various services running on the node. * 此API由集群上运行的Ambari代理调用，以更新节点上运行的各种服务的状态。 * * @response.representation.200.mediaType application/json * @response.representation.406.doc Error in heartbeat message format * @response.representation.408.doc Request Timed out * @param message Heartbeat message * @throws Exception */ @Path("heartbeat/{hostName}") @POST @Consumes(MediaType.APPLICATION_JSON) @Produces({MediaType.APPLICATION_JSON}) public HeartBeatResponse heartbeat(HeartBeat message) throws WebApplicationException { if (LOG.isDebugEnabled()) { LOG.debug("Received Heartbeat message " + message); } HeartBeatResponse heartBeatResponse; try { //处理心跳并返回响应 heartBeatResponse = hh.handleHeartBeat(message); if (LOG.isDebugEnabled()) { LOG.debug("Sending heartbeat response with response id " + heartBeatResponse.getResponseId()); LOG.debug("Response details " + heartBeatResponse); } } catch (Exception e) { LOG.warn("Error in HeartBeat", e); throw new WebApplicationException(500); } return heartBeatResponse; } /** * Retrieves the components category map for stack used on cluster * (Internal API to be used by Ambari agent). * 检索集群上使用的堆栈的组件类别映射（Ambari代理使用的内部API）。 * * @response.representation.200.doc This API is invoked by Ambari agent running * on a cluster to update the components category map of stack used by this cluster * 此API由集群上运行的Ambari代理调用，以更新此集群使用的堆栈的组件类别映射 * * @response.representation.200.mediaType application/json * @response.representation.408.doc Request Timed out * @param clusterName of cluster * @throws Exception */ @Path("components/{clusterName}") @GET @Produces({MediaType.APPLICATION_JSON}) public ComponentsResponse components( @PathParam("clusterName") String clusterName) { if (LOG.isDebugEnabled()) { LOG.debug("Received Components request for cluster " + clusterName); } ComponentsResponse componentsResponse; try { componentsResponse = hh.handleComponents(clusterName); if (LOG.isDebugEnabled()) { LOG.debug("Sending components response"); LOG.debug("Response details " + componentsResponse); } } catch (Exception e) { LOG.warn("Error in Components", e); throw new WebApplicationException(500); } return componentsResponse; } }