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From "Devaraj Das (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-312) Connections should not be cached
Date Thu, 24 Aug 2006 06:50:26 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-312?page=comments#action_12430160 ] 
            
Devaraj Das commented on HADOOP-312:
------------------------------------

>Threads should be cheap to create, but keeping too many 
>around can be expensive. Again, I think the life of the thread 
>should be the same as the life of the connection.

There are not many threads in the system. It is one per server (in the current version of
hadoop, it is a single digit number, maybe, 2 or 3). If connection life is 1 sec and if the
thread's life is same as the life of the connection, then a thread is destroyed/created ~once/second
per server. I really wanted to avoid creating/destroying threads that often.

> Connections should not be cached
> --------------------------------
>
>                 Key: HADOOP-312
>                 URL: http://issues.apache.org/jira/browse/HADOOP-312
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: ipc
>            Reporter: Devaraj Das
>         Assigned To: Devaraj Das
>         Attachments: no_conn_caching.patch, no_conn_caching.patch, no_conn_caching.patch,
no_connection_caching.patch, no_connection_caching.patch
>
>
> Servers and clients (client include datanodes, tasktrackers, DFSClients & tasks)
should not cache connections or maybe cache them for very short periods of time. Clients should
set up & tear down connections to the servers everytime they need to contact the servers
(including the heartbeats). If connection is cached, then reuse the existing connection for
a few subsequent transactions until the connection expires. The heartbeat interval should
be more so that many more clients (order of  tens of thousands) can be accomodated within
1 heartbeat interval.

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