[ http://issues.apache.org/jira/browse/HADOOP-178?page=all ]
Doug Cutting resolved HADOOP-178:
---------------------------------
Fix Version: 0.2
Resolution: Fixed
I just committed this. Thanks, Hairong!
> piggyback block work requests to heartbeats and move block
> replication/deletion startup delay from datanodes to namenode
> ------------------------------------------------------------------------------------------------------------------------
>
> Key: HADOOP-178
> URL: http://issues.apache.org/jira/browse/HADOOP-178
> Project: Hadoop
> Type: Improvement
> Components: dfs
> Reporter: Hairong Kuang
> Assignee: Hairong Kuang
> Fix For: 0.2
> Attachments: startupDelay.patch
>
> Currently each datanode sends at least two messages to namenode within a
> heartbeat interval. One is a heartbeat message and another is block work
> request. By piggybacking the block work request to a heartbeat can greatly
> cut the number of messages between a datanode and the namenode.
> Secondly each datanode waits for a configurable "StartupPeriod" before it
> sends a block work request in order to avoid uneccessary block replication at
> startup time. But if the namenode starts much later than datanodes, this
> scheme does not work. Furthermore, the namenode has more information to
> decide when to send block work to datanodes. For example, all datanodes send
> block reports etc. It is more resonable to move the startup delay from
> datanodes to the namenode
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