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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-941) Datanode xceiver protocol should allow reuse of a connection
Date Thu, 24 Mar 2011 19:53:05 GMT

    [ https://issues.apache.org/jira/browse/HDFS-941?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13010879#comment-13010879
] 

stack commented on HDFS-941:
----------------------------

+1 on commit. Patch looks great though a bit hard to read because its mostly white-space changes.
 I like the tests.  I"m good w/ adding guava.

If a v6, here a few minor comment:

Javadoc on BlockReader is not properly formatted (will show as mess after html'ing) -- same
for class comment on DN.

gotEOS is odd name for a boolean, would think eos better?

Hard-codings like this, +    final int MAX_RETRIES = 3;, should be instead gotten from config.
even if not declared in hdfs-default.xml?  Same for DN_KEEPALIVE_TIMEOUT.

Why would we retry a socket that is throwing an IOE?  Why not close and move on with new socket?

Is SocketCache missing a copyright notice?

Is this the right thing to do?

{code}
+    SocketAddress remoteAddr = sock.getRemoteSocketAddress();
+    if (remoteAddr == null) {
+      return;
+    }
{code}

The socket is not cached because it does not have a remote address.  Why does it not have
a remote address.  Is there something wrong w/ the socket?  Should we throw and exception
or close and throw away the socket?

There is a tab at #1242 in patch:

{code}+	// restore normal timeout{code}






> Datanode xceiver protocol should allow reuse of a connection
> ------------------------------------------------------------
>
>                 Key: HDFS-941
>                 URL: https://issues.apache.org/jira/browse/HDFS-941
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: data-node, hdfs client
>    Affects Versions: 0.22.0
>            Reporter: Todd Lipcon
>            Assignee: bc Wong
>         Attachments: HDFS-941-1.patch, HDFS-941-2.patch, HDFS-941-3.patch, HDFS-941-3.patch,
HDFS-941-4.patch, HDFS-941-5.patch, hdfs941-1.png
>
>
> Right now each connection into the datanode xceiver only processes one operation.
> In the case that an operation leaves the stream in a well-defined state (eg a client
reads to the end of a block successfully) the same connection could be reused for a second
operation. This should improve random read performance significantly.

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