[jira] [Commented] (HDFS-15250) Setting `dfs.client.use.datanode.hostname` to true can crash the system because of unhandled UnresolvedAddressException

["Stephen O'Donnell (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HDFS-15250?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17326902#comment-17326902 ] 

Stephen O'Donnell commented on HDFS-15250:
------------------------------------------

I am reviewing some backports and came across this one. The change here does not seem to fix anything as a couple of people have stated. Has anyone got a stack trace from an occurrence of this error so we can see where it fails exactly?

> Setting `dfs.client.use.datanode.hostname` to true can crash the system because of unhandled UnresolvedAddressException
> -----------------------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-15250
>                 URL: https://issues.apache.org/jira/browse/HDFS-15250
>             Project: Hadoop HDFS
>          Issue Type: Bug
>            Reporter: Ctest
>            Assignee: Ctest
>            Priority: Major
>             Fix For: 3.2.2, 3.3.1, 3.4.0, 3.1.5
>
>         Attachments: HDFS-15250-001.patch, HDFS-15250-002.patch
>
>
> *Problem:*
> `dfs.client.use.datanode.hostname` by default is set to false, which means the client will use the IP address of the datanode to connect to the datanode, rather than the hostname of the datanode.
> In `org.apache.hadoop.hdfs.client.impl.BlockReaderFactory.nextTcpPeer`:
>  
> {code:java}
>  try {
>    Peer peer = remotePeerFactory.newConnectedPeer(inetSocketAddress, token,
>        datanode);
>    LOG.trace("nextTcpPeer: created newConnectedPeer {}", peer);
>    return new BlockReaderPeer(peer, false);
>  } catch (IOException e) {
>    LOG.trace("nextTcpPeer: failed to create newConnectedPeer connected to"
>        + "{}", datanode);
>    throw e;
>  }
> {code}
>  
> If `dfs.client.use.datanode.hostname` is false, then it will try to connect via IP address. If the IP address is illegal and the connection fails, IOException will be thrown from `newConnectedPeer` and be handled.
> If `dfs.client.use.datanode.hostname` is true, then it will try to connect via hostname. If the hostname cannot be resolved, UnresolvedAddressException will be thrown from `newConnectedPeer`. However, UnresolvedAddressException is not a subclass of IOException so `nextTcpPeer` doesn’t handle this exception at all. This unhandled exception could crash the system.
>  
> *Solution:*
> Since the method is handling the illegal IP address, then the illegal hostname should be also handled as well. One solution is to add the handling logic in `nextTcpPeer`:
> {code:java}
>  } catch (IOException e) {
>    LOG.trace("nextTcpPeer: failed to create newConnectedPeer connected to"
>        + "{}", datanode);
>    throw e;
>  } catch (UnresolvedAddressException e) {
>    ... // handling logic 
>  }{code}
> I am very happy to provide a patch to do this.



--
This message was sent by Atlassian Jira
(v8.3.4#803005)

---------------------------------------------------------------------
To unsubscribe, e-mail: hdfs-issues-unsubscribe@hadoop.apache.org
For additional commands, e-mail: hdfs-issues-help@hadoop.apache.org