I'm having trouble overriding the maximum number of map tasks that run on a given machine in my cluster. The default value of mapred.tasktracker.map.tasks.maximum is set to 2 in hadoop-default.xml. When running my job I passed
-jobconf mapred.tasktracker.map.tasks.maximum=1 to limit map tasks to one per machine but each machine was still allocated 2 map tasks (simultaneously). The only way I was able to guarantee a maximum of one map task per machine was to change the value of the property in hadoop-site.xml. This is unsatisfactory since I'll often be changing the maximum on a per job basis. Any hints? On a different note, when I attempt to pass params via -D I get a usage message; when I use -jobconf the command goes through (and works in the case of mapred.reduce.tasks=0 for example) but I get a deprecation warning). Thanks, John
