yarn查询/cluster/nodes均返回localhost

背景:

　　1、已禁用ipv6。

　　2、所有节点的/etc/hosts正确配置，任务在ResourceManager提交。

　　3、yarn-site.xml中指定了

　　　　yarn.resourcemanager.hostname=Master
　　　　yarn.nodemanager.aux-services=mapreduce_shuffle
　　　　并在各NodeManager配置了相应的yarn.nodemanager.hostname

 4、mapred-site.xml中指定了mapreduce.framework.name=yarn

现象：

　　提交MR任务的连接拒绝的堆栈，其中连接的container地址为localhost，与实际需要的不一致。

ser:	root
Name:	Bigdata-Hadoop-1.0-SNAPSHOT.jar
Application Type:	MAPREDUCE
Application Tags:
YarnApplicationState:	FAILED
Queue:	default
FinalStatus Reported by AM:	FAILED
Started:	Thu Nov 22 21:59:31 +0800 2018
Elapsed:	6mins, 1sec
Tracking URL:	History
Diagnostics:	Application application_1542889591013_0006 failed 2 times due to Error launching appattempt_1542889591013_0006_000002. Got exception: java.net.ConnectException: Call From localhost/127.0.0.1 to localhost:33070 failed on connection exception: java.net.ConnectException: Connection refused; For more details see: http://wiki.apache.org/hadoop/ConnectionRefused at sun.reflect.GeneratedConstructorAccessor59.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:423) at org.apache.hadoop.net.NetUtils.wrapWithMessage(NetUtils.java:792) at org.apache.hadoop.net.NetUtils.wrapException(NetUtils.java:732) at org.apache.hadoop.ipc.Client.call(Client.java:1480) at org.apache.hadoop.ipc.Client.call(Client.java:1413) at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:229) at com.sun.proxy.$Proxy83.startContainers(Unknown Source) at org.apache.hadoop.yarn.api.impl.pb.client.ContainerManagementProtocolPBClientImpl.startContainers(ContainerManagementProtocolPBClientImpl.java:96) at sun.reflect.GeneratedMethodAccessor19.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:191) at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:102) at com.sun.proxy.$Proxy84.startContainers(Unknown Source) at org.apache.hadoop.yarn.server.resourcemanager.amlauncher.AMLauncher.launch(AMLauncher.java:119) at org.apache.hadoop.yarn.server.resourcemanager.amlauncher.AMLauncher.run(AMLauncher.java:250) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748) Caused by: java.net.ConnectException: Connection refused at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method) at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:717) at org.apache.hadoop.net.SocketIOWithTimeout.connect(SocketIOWithTimeout.java:206) at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:531) at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:495) at org.apache.hadoop.ipc.Client$Connection.setupConnection(Client.java:615) at org.apache.hadoop.ipc.Client$Connection.setupIOstreams(Client.java:713) at org.apache.hadoop.ipc.Client$Connection.access$2900(Client.java:376) at org.apache.hadoop.ipc.Client.getConnection(Client.java:1529) at org.apache.hadoop.ipc.Client.call(Client.java:1452) ... 15 more . Failing the application.

同时在底部的两次尝试时，driver地址也为localhost

通过查询发现yarn返回的集群节点信息中，所有的NodeManager地址均为localhost。

以上均证实通过yarn查询到的NodeManager地址异常，无法远程调用NodeManager来启动Container，直接导致MR任务失败。

方案：

　　1、四方博客，撸遍全网，无果。

　　2、游走各群，虚心请教，无果。

　　3、自力更生，强撸源码，待续 ... ...

源码：

　　找不到入口就别看了。

　　org/apache/hadoop/yarn/server/resourcemanager/webapp/RMWebServices.java:252

  @GET
  @Path("/nodes")
  @Produces({ MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML })
  public NodesInfo getNodes(@QueryParam("states") String states) {
    init();
    ResourceScheduler sched = this.rm.getResourceScheduler();
    if (sched == null) {
      throw new NotFoundException("Null ResourceScheduler instance");
    }

    EnumSet<NodeState> acceptedStates;
    if (states == null) {
      acceptedStates = EnumSet.allOf(NodeState.class);
    } else {
      acceptedStates = EnumSet.noneOf(NodeState.class);
      for (String stateStr : states.split(",")) {
        acceptedStates.add(
            NodeState.valueOf(StringUtils.toUpperCase(stateStr)));
      }
    }

    Collection<RMNode> rmNodes = RMServerUtils.queryRMNodes(this.rm.getRMContext(),
        acceptedStates);
    NodesInfo nodesInfo = new NodesInfo();
    for (RMNode rmNode : rmNodes) {
      NodeInfo nodeInfo = new NodeInfo(rmNode, sched);
      if (EnumSet.of(NodeState.LOST, NodeState.DECOMMISSIONED, NodeState.REBOOTED)
          .contains(rmNode.getState())) {
        nodeInfo.setNodeHTTPAddress(EMPTY);
      }
      nodesInfo.add(nodeInfo);
    }

    return nodesInfo;
  }

　　这里在生成的节点信息。

　　org/apache/hadoop/yarn/server/resourcemanager/webapp/dao/NodeInfo.java:57

public NodeInfo(RMNode ni, ResourceScheduler sched) {
    NodeId id = ni.getNodeID();
    SchedulerNodeReport report = sched.getNodeReport(id);
    this.numContainers = 0;
    this.usedMemoryMB = 0;
    this.availMemoryMB = 0;
    if (report != null) {
      this.numContainers = report.getNumContainers();
      this.usedMemoryMB = report.getUsedResource().getMemory();
      this.availMemoryMB = report.getAvailableResource().getMemory();
      this.usedVirtualCores = report.getUsedResource().getVirtualCores();
      this.availableVirtualCores = report.getAvailableResource().getVirtualCores();
    }
    this.id = id.toString();
    this.rack = ni.getRackName();
    this.nodeHostName = ni.getHostName();
    this.state = ni.getState();
    this.nodeHTTPAddress = ni.getHttpAddress();
    this.lastHealthUpdate = ni.getLastHealthReportTime();
    this.healthReport = String.valueOf(ni.getHealthReport());

　　三个关键信息全是ni这个怪胎来的，那就看你怎么来的行不。

　　org/apache/hadoop/yarn/server/resourcemanager/RMServerUtils.java:63

 public static List<RMNode> queryRMNodes(RMContext context,
      EnumSet<NodeState> acceptedStates) {
    // nodes contains nodes that are NEW, RUNNING OR UNHEALTHY
    ArrayList<RMNode> results = new ArrayList<RMNode>();
    if (acceptedStates.contains(NodeState.NEW) ||
        acceptedStates.contains(NodeState.RUNNING) ||
        acceptedStates.contains(NodeState.UNHEALTHY)) {
      for (RMNode rmNode : context.getRMNodes().values()) {
        if (acceptedStates.contains(rmNode.getState())) {
          results.add(rmNode);
        }
      }
    }

　　看来这个context里有点东西，具体怎么初始化这个context下回再研究，先看里面对RMNodes的操作。

　　接下的时间里就是在跟Yarn挣扎，但是事实证明并不能找到这个hostname究竟是怎么成了localhost，而不是期望的工作节的hostname。毕竟代码量不少，里面错综复杂，还需要点时间缕缕，那就下次接着看源码。不过在了解了一定原理后，搂一遍源码确实对理解原理还是蛮有效的。

　　虽然看源码没有得到想要的结果，但是有个大胆想法：通过IP解析hostname是取hosts文件里IP匹配上的第一个hostname（待确认）。因此就将工作节点的ip和hostname挪到第一行，重启yarn集群，MR任务瞬间畅通。