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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-2346) DataNode should have timeout on socket writes.
Date Fri, 29 Feb 2008 20:14:51 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-2346?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12573932#action_12573932
] 

Tsz Wo (Nicholas), SZE commented on HADOOP-2346:
------------------------------------------------

- For ProviderInfo.next, I agreed that your implementation is more efficient and use less
memory.  +1 since this class is a low level class.

- >This won't work because most channels are both Readable and Writable.
Actually, I think the boolean variable read can be eliminated.  See below.

- > Can't really eliminate runtime checking. For e.g. SocketInputStream's channel should
be both SelectableChannel and a ReadableByteChannel. How do we enforce that without runtime
check?

In the constructor of SocketIOWithTimeout, you already enforce if read is true, channel must
be a ReadableByteChannel, otherwise, channel must be a WritableByteChannel.  I do not see
a good reason to put ReadableByteChannel and WritableByteChannel in the same class and use
a boolean to remember whether it is doing read or write.

I suggest to add two classes, say ReadableSocketIOWithTimeout and WritableSocketIOWithTimeout,
both extending SocketIOWithTimeout.  Then, the fields layout will become:
{code}
abstract class SocketIOWithTimeout {
  private long timeout;
  private boolean closed = false;
}

class ReadableSocketIOWithTimeout extends SocketIOWithTimeout {
  private ReadableByteChannel in;
}

class WritableSocketIOWithTimeout extends SocketIOWithTimeout {
  private WritableByteChannel out;
}
{code}

- Also found some typs in SocketIOWithTimeout.java 
line 59, /* => /**
line 119, mutliple => multiple
line 247, canceled => canceled


> DataNode should have timeout on socket writes.
> ----------------------------------------------
>
>                 Key: HADOOP-2346
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2346
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: dfs
>    Affects Versions: 0.15.1
>            Reporter: Raghu Angadi
>            Assignee: Raghu Angadi
>             Fix For: 0.17.0
>
>         Attachments: HADOOP-2346.patch, HADOOP-2346.patch, HADOOP-2346.patch, HADOOP-2346.patch,
HADOOP-2346.patch, HADOOP-2346.patch, HADOOP-2346.patch, HADOOP-2346.patch, HADOOP-2346.patch,
HADOOP-2346.patch, HADOOP-2346.patch
>
>
> If a client opens a file and stops reading in the middle, DataNode thread writing the
data could be stuck forever. For DataNode sockets we set read timeout but not write timeout.
I think we should add a write(data, timeout) method in IOUtils that assumes it the underlying
FileChannel is non-blocking.

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