private void validateNumberOfTasks ( int splits , int reduceTasks , JobConf conf ) throws IOException { int maxTasks = conf . getInt ( "mapred.jobtracker.maxtasks.per.job" , - 1 ) ; int totalTasks = splits + reduceTasks ; if ( ( maxTasks != - 1 ) && ( totalTasks > maxTasks ) ) { throw new IOException ( "The number of tasks for this job " + totalTasks + " exceeds the configured limit " + maxTasks ) ; } }
JobTrcker applies this limit against the sum of mappers and reducers .