Mailing-List: contact common-issues-help@hadoop.apache.org; run by ezmlm
Precedence: bulk
Reply-To: common-issues@hadoop.apache.org
Message-ID: <32681971.292061290624797101.JavaMail.jira@thor>
Date: Wed, 24 Nov 2010 13:53:17 -0500 (EST)
From: "Sanjay Radia (JIRA)" <jira@apache.org>
To: common-issues@hadoop.apache.org
Subject: [jira] Commented: (HADOOP-6904) A baby step towards inter-version
 communications between dfs client and NameNode
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit


    [ https://issues.apache.org/jira/browse/HADOOP-6904?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12935440#action_12935440 ] 

Sanjay Radia commented on HADOOP-6904:
--------------------------------------

On further thought, the Major-minor removes most of the switch statements. Having the list of the server method names simplifies the if statement:

With M-m:
{code}
  list() {
    if (m >= xxx)  {
        dfsclient.iterateList(..)
   } else {
       dfsclient.list(...)
  }
{code}

With method names
{code}
  if (server.hasMethod(iterateListSignature) {
        dfsclient.iterateList(..)
   } else {
       dfsclient.list(...)
  }
{code}
      

> A baby step towards inter-version communications between dfs client and NameNode
> --------------------------------------------------------------------------------
>
>                 Key: HADOOP-6904
>                 URL: https://issues.apache.org/jira/browse/HADOOP-6904
>             Project: Hadoop Common
>          Issue Type: New Feature
>          Components: ipc
>    Affects Versions: 0.22.0
>            Reporter: Hairong Kuang
>            Assignee: Hairong Kuang
>             Fix For: 0.22.0
>
>         Attachments: majorMinorVersion.patch, rpcVersion.patch, rpcVersion1.patch
>
>
> Currently RPC communications in Hadoop is very strict. If a client has a different version from that of the server, a VersionMismatched exception is thrown and the client can not connect to the server. This force us to update both client and server all at once if a RPC protocol is changed. But sometime different versions do not mean the client & server are not compatible. It would be nice if we could relax this restriction and allows us to support inter-version communications.
> My idea is that DfsClient catches VersionMismatched exception when it connects to NameNode. It then checks if the client & the server is compatible. If yes, it sets the NameNode version in the dfs client and allows the client to continue talking to NameNode. Otherwise, rethrow the VersionMismatch exception.

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.