The number of map and reduce slots determines the number of concurrent map/reduce tasks for a TaskTracker, which forks multiple JVMs to run these tasks. In this recipe, we will give you a general view of setting proper number of these slots for the TaskTracker.
We assume that the Hadoop cluster has been properly configured and all the daemons are running without any issues.
Log in from the Hadoop cluster administrator machine to the cluster master node using the following command:
ssh hduser@master
Use the following steps to configure map/reduce slots for a TaskTracker:
Stop the MapReduce cluster with the following command:
stop-mapred.sh
Configure the map slots by adding the following property into the
$HADOOP_HOME/conf/mapred-site.xml
file:<property> <name>mapred.takstracker.map.tasks.maximum</name> <value>4</value> </property>