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https://issues.apache.org/jira/browse/HADOOP-1093?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12486472
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dhruba borthakur commented on HADOOP-1093:
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I am not too inclined to check if the last block has achieved its minimum
replication factor before allocating the next block. The datanodes directly
send block confirmation to the namenode and a slow datanode for even one block
of the file is going to adversely impact write performance.
But I agree with you that we need to slow down the client if the namenode is
overloaded? If the addBlock() RPC times out, maybe the client should retry?
> NNBench generates millions of NotReplicatedYetException in Namenode log
> -----------------------------------------------------------------------
>
> Key: HADOOP-1093
> URL: https://issues.apache.org/jira/browse/HADOOP-1093
> Project: Hadoop
> Issue Type: Bug
> Components: dfs
> Affects Versions: 0.12.0
> Reporter: Nigel Daley
> Assigned To: dhruba borthakur
> Fix For: 0.13.0
>
> Attachments: nyr2.patch
>
>
> Running NNBench on latest trunk (0.12.1 candidate) on a few hundred nodes
> yielded 2.3 million of these exceptions in the NN log:
> 2007-03-08 09:23:03,053 INFO org.apache.hadoop.ipc.Server: IPC Server
> handler 0 on 8020 call error:
> org.apache.hadoop.dfs.NotReplicatedYetException: Not replicated yet
> at
> org.apache.hadoop.dfs.FSNamesystem.getAdditionalBlock(FSNamesystem.java:803)
> at org.apache.hadoop.dfs.NameNode.addBlock(NameNode.java:309)
> at sun.reflect.GeneratedMethodAccessor14.invoke(Unknown Source)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
> at java.lang.reflect.Method.invoke(Method.java:597)
> at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:336)
> at org.apache.hadoop.ipc.Server$Handler.run(Server.java:559)
> I run NNBench to create files with block size set to 1 and replication set to
> 1. NNBench then writes 1 byte to the file. Minimum replication for the
> cluster is the default, ie 1. If it encounters an exception while trying to
> do either the create or write operations, it loops and tries again. Multiply
> this by 1000 files per node and a few hundred nodes.
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