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From "Chris Schneider (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-406) Tasks launched by tasktracker in separate JVM can't generate log output
Date Tue, 01 Aug 2006 16:47:18 GMT
     [ http://issues.apache.org/jira/browse/HADOOP-406?page=all ]

Chris Schneider updated HADOOP-406:

    Attachment: HADOOP-406.patch

Here's a patch that provides one solution to the problem.

I modified TaskRunner.java so that it supports elements like -Dhadoop.log.dir=@property[hadoop.log.dir]@
within the mapred.child.java.opts Hadoop configuration property (replacing @property[hadoop.log.dir]@
with this property value).

If others agree that this is the appropriate way to solve the problem, then we should probably
modify mapred.child.java.opts in hadoop-default.xml to include all 5 of the items in the default
$HADOOP_OPTS (hadoop.log.dir, hadoop.log.file, hadoop.home.dir, hadoop.id.str, and hadoop.root.logger),
using this method. A few notes, though:

1) This creates yet another dependency on the contents of $HADOOP_OPTS (i.e., anyone that
adds items to this should probably add them to mapred.child.java.opts as well.) This is less
than elegant.

2) It doesn't seem like hadoop.home.dir, hadoop.id.str, and hadoop.root.logger are actually
being used currently by the code. Both hadoop.home.dir and hadoop.id.str are loaded by LogFormatter.initFileHandler(),
but that method doesn't seem to be used by anyone. It doesn't seem like anyone is loading
hadoop.root.logger at all.

> Tasks launched by tasktracker in separate JVM can't generate log output
> -----------------------------------------------------------------------
>                 Key: HADOOP-406
>                 URL: http://issues.apache.org/jira/browse/HADOOP-406
>             Project: Hadoop
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.4.0
>            Reporter: Chris Schneider
>         Attachments: HADOOP-406.patch
> Child JVM's don't have access to logging config system properties. When the child JVM
gets launched, it doesn't inherit the Java system properties hadoop.log.dir and hadoop.log.file
(which are actually based on the Bash environment variables $HADOOP_LOG_DIR and $HADOOP_LOGFILE).
This means that you get no log messages from the actual map/reduce tasks that are executing.
> Stefan Groschupf reported this problem a while back:
> -------------------------------------------------------------------------
> To: hadoop-dev@lucene.apache.org
> From: Stefan Groschupf <sg@media-style.com>
> Subject: tasks can't log bug?
> Date: Tue, 25 Jul 2006 19:26:17 -0700
> X-Virus-Checked: Checked by ClamAV on apache.org
> Hi Hadoop developers,
> I'm confused about the way logging works within map or reduce tasks.
> Since tasks are launched in a new JVM  the java system properties "hadoop.log.dir" and
"hadoop.log.file" are not passed to the new JVM.
> This prevents the child process from logging properly. In fact you get:
>  java.io.FileNotFoundException: / (Is a directory)
>   at java.io.FileOutputStream.openAppend(Native Method)
>   at java.io.FileOutputStream.<init>(FileOutputStream.java:177)
>   at java.io.FileOutputStream.<init>(FileOutputStream.java:102)
>   at org.apache.log4j.FileAppender.setFile(FileAppender.java:289)
>   at org.apache.log4j.RollingFileAppender.setFile(RollingFileAppender.java:165)
>   at org.apache.log4j.FileAppender.activateOptions(FileAppender.java:163)
>   at org.apache.log4j.config.PropertySetter.activate(PropertySetter.java:256)
>   at org.apache.log4j.config.PropertySetter.setProperties(PropertySetter.java:132)
>   at org.apache.log4j.config.PropertySetter.setProperties(PropertySetter.java:96)
>   at org.apache.log4j.PropertyConfigurator.parseAppender(PropertyConfigurator.java:654)
>   at org.apache.log4j.PropertyConfigurator.parseCategory(PropertyConfigurator.java:612)
>   at org.apache.log4j.PropertyConfigurator.configureRootCategory(PropertyConfigurator.j
> 2006-07-25 15:59:07,553 INFO  mapred.TaskTracker (TaskTracker.java:main(993)) - Child
>   at org.apache.log4j.PropertyConfigurator.doConfigure(PropertyConfigurator.java:415)
>   at org.apache.log4j.PropertyConfigurator.doConfigure(PropertyConfigurator.java:441)
>   at org.apache.log4j.helpers.OptionConverter.selectAndConfigure(OptionConverter.java:4
>   at org.apache.log4j.LogManager.<clinit>(LogManager.java:122)
>   at org.apache.log4j.Logger.getLogger(Logger.java:104)
>   at org.apache.commons.logging.impl.Log4JLogger.getLogger(Log4JLogger.java:229)
>   at org.apache.commons.logging.impl.Log4JLogger.<init>(Log4JLogger.java:65)
>   at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
>   at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImp
>   at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAcc
>   at java.lang.reflect.Constructor.newInstance(Constructor.java:494)
>   at org.apache.commons.logging.impl.LogFactoryImpl.newInstance(LogFactoryImpl.java:529
>   at org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactoryImpl.java:235
>   at org.apache.commons.logging.LogFactory.getLog(LogFactory.java:370)
>   at org.apache.hadoop.mapred.TaskTracker.<clinit>(TaskTracker.java:44)
>   at org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:993)
> We see several ways to solve this problem. First retrieve the properties "hadoop.log.dir"
and "hadoop.log.file" from the mother JVM and then pass them to the child JVM as within the
args parameter.
> Second would be to  access the environment variables "$HADOOP_LOG_DIR" and "$HADOOP_LOGFILE"
using System.getEnv (java 1.5).
> Third there would be a more general solution. Taskrunner would resolve any environment
variables it found in "mapred.child.java.opts" by lookup the value using System.getEnv().
> Eg:
> unix:
> export MAX_MEMORY = 200
> hadoop-site.xml:
> <name>mapred.child.java.opts</name>
> <value>-Xmx${MAX_MEMORY}</value>

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