使用Java SDK从AWS EMR集群获取主公共DNS值

我需要通过Java SDK获取主公共DNS值。在应用程序开始时，我将获得的唯一信息是ClusterName，它是静态的

到目前为止，我已经能够提取出我需要的所有其他信息，除了这个和这个，不幸的是，对于应用程序的成功至关重要

这是我目前正在使用的代码：

List<ClusterSummary> summaries = clusters.getClusters();
        for (ClusterSummary cs: summaries) {
            if (cs.getName().equals("test") && WHITELIST.contains(cs.getStatus().getState())) {
                ListInstancesResult instances = emr.listInstances(new ListInstancesRequest().withClusterId(cs.getId()));
                clusterHostName = instances.getInstances().get(0).toString();
                jobFlowId = cs.getId();
            }
        }

---

不要使用ListInstances。相反，使用DescribeCluster，它作为MasterPublicDnsName字段之一返回。

来扩展Jonathon提到的内容：

        AmazonEC2Client ec2 = new AmazonEC2Client(cred);
    DescribeInstancesResult describeInstancesResult = ec2.describeInstances(new DescribeInstancesRequest().withInstanceIds(clusterInstanceIds));
    List<Reservation> reservations = describeInstancesResult.getReservations();
    for (Reservation res : reservations) {
        for (GroupIdentifier group : res.getGroups()) {
            if (group.getGroupName().equals("ElasticMapReduce-master")) { // yaaaaaaaaah, Wahay!
                masterDNS = res.getInstances().get(0).getPublicDnsName();
            }
        }
    }

AmazonEC2Client ec2=新的AmazonEC2Client（cred）；
DescribeInstancesResult DescribeInstancesResult=ec2.describeInstances（新的DescribeInstancesRequest（）。带有InstanceId（ClusterInstanceId））；
List reservations=descripbeinstancesresult.getReservations（）；
对于（预订：预订）{
对于（GroupIdentifier组：res.getGroups（））{
如果（group.getGroupName（）.equals（“ElasticMapReduce master”）{//yaaaaaaaah，哇！
masterDNS=res.getInstances（）.get（0.getPublicDnsName（）；
}
}
}

---

下面是获取公共DNS名称的工作代码。

是的，我应该早点结束这个问题，谢谢！

        AmazonEC2Client ec2 = new AmazonEC2Client(cred);
    DescribeInstancesResult describeInstancesResult = ec2.describeInstances(new DescribeInstancesRequest().withInstanceIds(clusterInstanceIds));
    List<Reservation> reservations = describeInstancesResult.getReservations();
    for (Reservation res : reservations) {
        for (GroupIdentifier group : res.getGroups()) {
            if (group.getGroupName().equals("ElasticMapReduce-master")) { // yaaaaaaaaah, Wahay!
                masterDNS = res.getInstances().get(0).getPublicDnsName();
            }
        }
    }

 AWSCredentials credentials_profile = null;
 credentials_profile = new 
 DefaultAWSCredentialsProviderChain().getCredentials();

 AmazonElasticMapReduceClient emr = new 
 AmazonElasticMapReduceClient(credentials_profile);
    Region euWest1 = Region.getRegion(Regions.US_EAST_1);
    emr.setRegion(euWest1);
 DescribeClusterFunction fun = new DescribeClusterFunction(emr);
    DescribeClusterResult res = fun.apply(new 
 DescribeClusterRequest().withClusterId(clusterId));
    String publicDNSName =res.getCluster().getMasterPublicDnsName();