how to write java Log file using the logger api while using hadoop

Hadoop comes with preconfigured log4j. All you have to do is import two classes:

import org.apache.commons.logging.Log;import org.apache.commons.logging.LogFactory;

And now you can define logger inside your mappers, reducers and wherever you want:

private static final Log LOG = LogFactory.getLog(MyClass.class);

And log what you need:

LOG.info("My message");

The messages will show up during job execution. You can tweak log4j configuration with

conf/log4j.properties

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