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From "Thomas Graves (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-1670) aggregated log writer can write more log data then it says is the log length
Date Fri, 21 Mar 2014 19:49:45 GMT

    [ https://issues.apache.org/jira/browse/YARN-1670?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13943464#comment-13943464

Thomas Graves commented on YARN-1670:

Good catch Jon.  Yep I think you are correct here.  We can actually still write more then
we should. It should be checking to make sure the curRead + len read is < fileLength before
writing and if its not only writing the difference.  

> aggregated log writer can write more log data then it says is the log length
> ----------------------------------------------------------------------------
>                 Key: YARN-1670
>                 URL: https://issues.apache.org/jira/browse/YARN-1670
>             Project: Hadoop YARN
>          Issue Type: Bug
>    Affects Versions: 3.0.0, 0.23.10, 2.2.0
>            Reporter: Thomas Graves
>            Assignee: Mit Desai
>            Priority: Critical
>             Fix For: 2.4.0
>         Attachments: YARN-1670-b23.patch, YARN-1670-v2-b23.patch, YARN-1670-v2.patch,
YARN-1670-v3-b23.patch, YARN-1670-v3.patch, YARN-1670.patch, YARN-1670.patch
> We have seen exceptions when using 'yarn logs' to read log files. 
> at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
>        at java.lang.Long.parseLong(Long.java:441)
>        at java.lang.Long.parseLong(Long.java:483)
>        at org.apache.hadoop.yarn.logaggregation.AggregatedLogFormat$LogReader.readAContainerLogsForALogType(AggregatedLogFormat.java:518)
>        at org.apache.hadoop.yarn.logaggregation.LogDumper.dumpAContainerLogs(LogDumper.java:178)
>        at org.apache.hadoop.yarn.logaggregation.LogDumper.run(LogDumper.java:130)
>        at org.apache.hadoop.yarn.logaggregation.LogDumper.main(LogDumper.java:246)
> We traced it down to the reader trying to read the file type of the next file but where
it reads is still log data from the previous file.  What happened was the Log Length was written
as a certain size but the log data was actually longer then that.  
> Inside of the write() routine in LogValue it first writes what the logfile length is,
but then when it goes to write the log itself it just goes to the end of the file.  There
is a race condition here where if someone is still writing to the file when it goes to be
aggregated the length written could be to small.
> We should have the write() routine stop when it writes whatever it said was the length.
 It would be nice if we could somehow tell the user it might be truncated but I'm not sure
of a good way to do this.
> We also noticed that a bug in readAContainerLogsForALogType where it is using an int
for curRead whereas it should be using a long. 
>       while (len != -1 && curRead < fileLength) {
> This isn't actually a problem right now as it looks like the underlying decoder is doing
the right thing and the len condition exits.

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