[ http://issues.apache.org/jira/browse/HADOOP-406?page=comments#action_12431047 ] Doug Cutting commented on HADOOP-406: -------------------------------------
The way this is currently supposed to work is that child processes log to standard output, and standard output is logged by the parent process (the task tracker). Is that not working for you? Longer-term, we probably do not want child processes opening log files directly. Rather, they should be configured with a logger that, for each line logged, makes an RPC to the parent process, passing the level and log message. Then the tasktracker can log things accordingly. > 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 <[EMAIL PROTECTED]> > 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> -- This message is automatically generated by JIRA. - If you think it was sent incorrectly contact one of the administrators: http://issues.apache.org/jira/secure/Administrators.jspa - For more information on JIRA, see: http://www.atlassian.com/software/jira
