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https://issues.apache.org/jira/browse/HDFS-3990?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13508889#comment-13508889
]
Chris Nauroth commented on HDFS-3990:
-------------------------------------
The problem I observe is that a server accepts a client socket connection, gets
the connection's InetAddress, and then getHostName returns "127.0.0.1". Below
is a short code sample that demonstrates the problem. This is a very rough
approximation of the IPC Server/Connection and DatanodeManager logic. When I
run this server on Mac, it prints "connection from hostName = localhost,
hostAddress = 127.0.0.1, canonicalHostName = localhost" for any client
connection. On Windows, it prints "connection from hostName = 127.0.0.1,
hostAddress = 127.0.0.1, canonicalHostName = 127.0.0.1".
{code}
package cnauroth;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.channels.ServerSocketChannel;
class Main {
public static void main(String[] args) throws Exception {
ServerSocket ss = ServerSocketChannel.open().socket();
ss.bind(new InetSocketAddress("localhost", 1234), 0);
System.out.println("ss = " + ss);
for (;;) {
Socket s = ss.accept();
InetAddress addr = s.getInetAddress();
System.out.println("connection from hostName = " + addr.getHostName() +
", hostAddress = " + addr.getHostAddress() + ", canonicalHostName = " +
addr.getCanonicalHostName());
PrintWriter pw = new PrintWriter(s.getOutputStream());
pw.println("hello");
pw.close();
s.close();
}
}
}
{code}
> NN's health report has severe performance problems
> --------------------------------------------------
>
> Key: HDFS-3990
> URL: https://issues.apache.org/jira/browse/HDFS-3990
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Affects Versions: 0.23.0, 2.0.0-alpha, 3.0.0
> Reporter: Daryn Sharp
> Assignee: Daryn Sharp
> Priority: Critical
> Fix For: 3.0.0, 2.0.3-alpha, 0.23.5
>
> Attachments: HDFS-3990.branch-0.23.patch,
> HDFS-3990.branch-0.23.patch, HDFS-3990.patch, HDFS-3990.patch,
> HDFS-3990.patch, HDFS-3990.patch, HDFS-3990.patch, HDFS-3990.patch,
> HDFS-3990.patch, HDFS-3990.patch, hdfs-3990.txt, hdfs-3990.txt
>
>
> The dfshealth page will place a read lock on the namespace while it does a
> dns lookup for every DN. On a multi-thousand node cluster, this often
> results in 10s+ load time for the health page. 10 concurrent requests were
> found to cause 7m+ load times during which time write operations blocked.
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