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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-312) Connections should not be cached
Date Wed, 23 Aug 2006 17:30:14 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-312?page=comments#action_12430052 ] 
Doug Cutting commented on HADOOP-312:

A few more issues:

The IS_CACHING_DISABLED field should not be all caps, since it is not a constant.

When connection caching is disabled then the connection threads should exit when there are
no outstanding responses.  Then the connections.remove(address) could also be moved to Connection.close(),
removing some duplicate logic.

Finally, the check of 'cachingDisabled' could be moved to be inside of incrementRef and decrementRef,
rather than around each call, changing these to something like:

private void incrementRef() {
  if (cachingDisabled) {
  synchronized (this) {

> 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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