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From "Xiaobing Zhou (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-10986) DFSAdmin should log detailed error message if any
Date Wed, 12 Oct 2016 00:01:45 GMT

    [ https://issues.apache.org/jira/browse/HDFS-10986?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15567015#comment-15567015
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Xiaobing Zhou commented on HDFS-10986:
--------------------------------------

Good catch for the hard coded ip and port, thanks for the patch. LGTM +1.

> DFSAdmin should log detailed error message if any
> -------------------------------------------------
>
>                 Key: HDFS-10986
>                 URL: https://issues.apache.org/jira/browse/HDFS-10986
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: tools
>            Reporter: Mingliang Liu
>            Assignee: Mingliang Liu
>         Attachments: HDFS-10986-branch-2.8.002.patch, HDFS-10986-branch-2.8.003.patch,
HDFS-10986.000.patch, HDFS-10986.001.patch, HDFS-10986.002.patch, HDFS-10986.003.patch
>
>
> There are some subcommands in {{DFSAdmin}} that swallow IOException and give very limited
error message, if any, to the stderr.
> {code}
> $ hdfs dfsadmin -getBalancerBandwidth 127.0.0.1:9866
> Datanode unreachable.
> $ hdfs dfsadmin -getDatanodeInfo localhost:9866
> Datanode unreachable.
> $ hdfs dfsadmin -evictWriters 127.0.0.1:9866
> $ echo $?
> -1
> {code}
> User is not able to get the exception stack even the LOG level is DEBUG. This is not
very user friendly. Fortunately, if the port number is not accessible (say 9999), users can
infer the detailed error message by IPC logs:
> {code}
> $ hdfs dfsadmin -getBalancerBandwidth 127.0.0.1:9999
> 2016-10-07 18:01:35,115 WARN util.NativeCodeLoader: Unable to load native-hadoop library
for your platform... using builtin-java classes where applicable
> 2016-10-07 18:01:36,335 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:9999.
Already tried 0 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10,
sleepTime=1000 MILLISECONDS)
> .....
> 2016-10-07 18:01:45,361 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:9999.
Already tried 9 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10,
sleepTime=1000 MILLISECONDS)
> 2016-10-07 18:01:45,362 WARN ipc.Client: Failed to connect to server: localhost/127.0.0.1:9999:
retries get failed due to exceeded maximum allowed retries number: 10
> java.net.ConnectException: Connection refused
> 	at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
> 	at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:717)
>         ...
> 	at org.apache.hadoop.hdfs.tools.DFSAdmin.run(DFSAdmin.java:2073)
> 	at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:76)
> 	at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:90)
> 	at org.apache.hadoop.hdfs.tools.DFSAdmin.main(DFSAdmin.java:2225)
> Datanode unreachable.
> {code}
> We should fix this by providing detailed error message. Actually, the {{DFSAdmin#run}}
already handles exception carefully, including:
> # set the exit ret value to -1
> # print the error message
> # log the exception stack trace (in DEBUG level)
> All we need to do is to not swallow exceptions without good reason.



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