Ah, that makes sense. Would it make sense to default the root logger to
the one defined in log4j.properties file instead of the static value in
the script then? That way an admin can set all logging properties
desired in the log4j.properties file, but can override with
HADOOP_ROOT_LOGGER to debug.
It feels a little black box-y that if HADOOP_ROOT_LOGGER isn't set then
the root logger set in log4j.properties is ignored.
Maybe this is all very well known and just a bit black box-y to me since
I'm new-ish to hadoop.
Rob
On 05/22/2014 03:41 PM, Colin McCabe wrote:
It's not always practical to edit the log4j.properties file. For one
thing, if you're using a management system, there may be many log4j
properties sprinkled around the system, and it could be difficult to figure
out which is the one you need to edit. For another, you may not (should
not?) have permission to do this on a production cluster.
Doing something like "HADOOP_ROOT_LOGGER="DEBUG,console" hadoop fs -cat
/foo" has helped me diagnose problems in the past.
best,
Colin
On Thu, May 22, 2014 at 6:34 AM, Robert Rati <rr...@redhat.com> wrote:
In my experience the default HADOOP_ROOT_LOGGER definition will override
any root logger defined in log4j.properties, which is where the problems
have arisen. If the HADOOP_ROOT_LOGGER definition in hadoop-config.sh were
removed, wouldn't the root logger defined in the log4j.properties file be
used? Or do the client commands not read that configuration file?
I'm trying to understand why the root logger should be defined outside of
the log4j.properties file.
Rob
On 05/22/2014 12:53 AM, Vinayakumar B wrote:
Hi Robert,
I understand your confusion.
HADOOP_ROOT_LOGGER is set to default value "INFO,console" if it hasn't set
for anything and logs will be displayed on the console itself.
This will be true for any client commands you run. For ex: "hdfs dfs -ls
/"
But for the server scripts (hadoop-daemon.sh, yarn-daemon.sh, etc)
HADOOP_ROOT_LOGGER will be set to "INFO, RFA" if HADOOP_ROOT_LOGGER env
variable is not defined.
So that all the log messages of the server daemons goto some log files and
this will be maintained by RollingFileAppender. If you want to override
all
these default and set your own loglevel then define that as env variable
HADOOP_ROOT_LOGGER.
For ex:
export HADOOP_ROOT_LOGGER="DEBUG,RFA"
export above env variable and then start server scripts or execute
client
commands, all logs goto files and will be maintained by
RollingFileAppender.
Regards,
Vinay
On Wed, May 21, 2014 at 6:42 PM, Robert Rati <rr...@redhat.com> wrote:
I noticed in hadoop-config.sh there is this line:
HADOOP_OPTS="$HADOOP_OPTS -Dhadoop.root.logger=${HADOOP_
ROOT_LOGGER:-INFO,console}"
which is setting a root logger if HADOOP_ROOT_LOGGER isn't set. Why is
this here.needed? There is a log4j.properties file provided that
defines a
default logger. I believe the line above will result in overriding
whatever is set for the root logger in the log4j.properties file. This
has
caused some confusion and hacks to work around this.
Is there a reason not to remove the above code and just have all the
logger definitions in the log4j.properties file? Is there maybe a
compatibility concern?
Rob
