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From Eric Baldeschwieler <eri...@yahoo-inc.com>
Subject Re: [jira] Assigned: (HADOOP-96) name server should log decisions that affect data: block creation, removal, replication
Date Fri, 31 Mar 2006 00:30:11 GMT
do we have an easy way of loading the some of the name nodes (and  
data nodes) local directories into HDFs space?  This is an easy trick  
that would make it trivial to apply map-reduce to distributed log  
grepping.  Should we add that?  Had good success with this sort of  
thing with previous systems.

EG.

hdfs://blah:6666/SYSTEM/namenodes/<host:port>/logs/

just points allows one to HDFS browse the logs directory of a name  
node.  Can then use the plan-9 trick of putting all kinds of API info  
into "files" on the data nodes (be they real files or CGI equivalents).

Should I file a bug on this?


On Mar 30, 2006, at 4:08 PM, Yoram Arnon (JIRA) wrote:

>      [ http://issues.apache.org/jira/browse/HADOOP-96?page=all ]
>
> Yoram Arnon reassigned HADOOP-96:
> ---------------------------------
>
>     Assign To: Hairong Kuang
>
>> name server should log decisions that affect data: block creation,  
>> removal, replication
>> --------------------------------------------------------------------- 
>> ------------------
>>
>>          Key: HADOOP-96
>>          URL: http://issues.apache.org/jira/browse/HADOOP-96
>>      Project: Hadoop
>>         Type: Improvement
>>   Components: dfs
>>     Versions: 0.1
>>     Reporter: Yoram Arnon
>>     Assignee: Hairong Kuang
>>     Priority: Critical
>
>>
>> currently, there's no way to analyze and debug DFS errors where  
>> blocks disapear.
>> name server should log its decisions that affect data, including  
>> block creation, removal, replication:
>> - block <b> created, assigned to datanodes A, B, ...
>> - datanode A dead, block <b> underreplicated(1), replicating to  
>> datanode C
>> - datanode B dead, block <b> underreplicated(2), replicating to  
>> datanode D
>> - datanode A alive, block <b> overreplicated, removing from  
>> datanode D
>> - block <removed> from datanodes C, D, ...
>> that will enable me to track down, two weeks later, a block that's  
>> missing from a file, and to debug the name server.
>> extra credit:
>> - rotate log file, as it might grow large
>> - make this behaviour optional/configurable
>
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