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Date: Mon, 10 Jul 2017 10:30:01 +0000 (UTC)
From: "Weiwei Yang (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.13085880.1499677645000.206153.1499682601527@Atlassian.JIRA>
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Subject: [jira] [Commented] (HDFS-12108) Hdfs tail -f command keeps printing
 the last line in loop when more data is not available
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archived-at: Mon, 10 Jul 2017 10:38:51 -0000


    [ https://issues.apache.org/jira/browse/HDFS-12108?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16080130#comment-16080130 ] 

Weiwei Yang commented on HDFS-12108:
------------------------------------

Hi [~nitiraj.rathore]

Thanks for reporting this issue. I am trying to reproduce it but seem cannot 

{noformat}
[wwei@localhost]$ echo "this is a line without ending char" > /tmp/test.log
[wwei@localhost]$ tr -d '\n' < /tmp/test.log > /tmp/test1.log
[wwei@localhost]$ cat -A /tmp/test1.log
this is a line without ending char[wwei@localhost]$

// put to hdfs and then tail
[wwei@localhost]$ ./bin/hdfs dfs -tail -f /test1.log
this is a line without ending char
{noformat}

can you help to provide more steps how to reproduce this? Thanks


> Hdfs tail -f command keeps printing the last line in loop when more data is not available
> -----------------------------------------------------------------------------------------
>
>                 Key: HDFS-12108
>                 URL: https://issues.apache.org/jira/browse/HDFS-12108
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs-client
>    Affects Versions: 2.7.3
>            Reporter: Nitiraj Singh Rathore
>
> I tried to do the simple tail -f expecting that new data will keep appearing on console, but I found out that in the absence of new data the last line of the file keeps printing again and again. See the below output. For clarification I have also pasted the output of cat command for the same file.
> bq. [hdfs@c6401 lib]$ hdfs dfs -tail -f /ats/active/application_1499594381431_0001/appattempt_1499594381431_0001_000001/domainlog-appattempt_1499594381431_0001_000001
> bq. {"id":"Tez_ATS_application_1499594381431_0001","readers":"*","writers":"hive"}
> bq. {"id":"Tez_ATS_application_1499594381431_0001_1","readers":"*","writers":"hive"}
> bq. {"id":"Tez_ATS_application_1499594381431_0001_1","readers":"*","writers":"hive"}
> bq. {"id":"Tez_ATS_application_1499594381431_0001_1","readers":"*","writers":"hive"}
> bq. {"id":"Tez_ATS_application_1499594381431_0001_1","readers":"*","writers":"hive"}
> bq. 
> bq. [hdfs@c6401 lib]$ hdfs dfs -cat  /ats/active/application_1499594381431_0001/appattempt_1499594381431_0001_000001/domainlog-appattempt_1499594381431_0001_000001
> bq. {"id":"Tez_ATS_application_1499594381431_0001","readers":"*","writers":"hive"}
> bq. {"id":"Tez_ATS_application_1499594381431_0001_1","readers":"*","writers":"hive"}[hdfs@c6401 lib]$


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