[jira] Updated: (HADOOP-5034) NameNode should send both both replication and deletion requests to DataNode in one reply to a heartbeat

["Hairong Kuang (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HADOOP-5034?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Hairong Kuang updated HADOOP-5034:
----------------------------------

    Attachment: blockTransferInvalidate.patch

Here is the patch that does the following:
1. ReplicationMonitor schedules both block replication and deletion in one iteration;
2. Heartbeat picks up both replication and deletion requests if both are scheduled;
3. BlockCommand is enhanced so that a command can carry both replication and deletion requests;
4. Datanode handles both replication and deletion requests when receive a heartbeat reply.

> NameNode should send both both replication and deletion requests to DataNode in one reply to a heartbeat
> --------------------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-5034
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5034
>             Project: Hadoop Core
>          Issue Type: New Feature
>          Components: dfs
>            Reporter: Hairong Kuang
>            Assignee: Hairong Kuang
>             Fix For: 0.21.0
>
>         Attachments: blockTransferInvalidate.patch
>
>
> Currently NameNode favors block replication requests over deletion requests. On reply to a heartbeat, NameNode does not send a block deletion request unless there is no block replication request. 
> This brings a problem when a near-full cluster loses a bunch of DataNodes. In react to the DataNode loss, NameNode starts to replicate blocks. However, replication takes a lot of cpu and a lot of replications fail because of the lack of disk space. So the administrator tries to delete some DFS files to free up space. However, block deletion requests get delayed for very long time because it takes a long time to drain the block replication requests for most DataNodes.
> I'd like to propose to let NameNode to send both replication requests and deletion requests to DataNodes in one reply to a heartbeat. This also implies that the replication monitor should schedule both replication and deletion work in one iteration.

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