for cli fans, In DFS side - ./bin/hadoop dfsadmin -report In MR side - ./bin/hadoop job -list-active-trackers
hth, P On Tue, Oct 11, 2011 at 5:27 AM, Uma Maheswara Rao G 72686 < [email protected]> wrote: > Hello Raimon, > > In DFS to know the DN status you can use getDataNodeStats API from > Distributed fileSystem. > > In MR, to know the number of active trackers, you can use getClusterStatus > from jobclient. It will give other stats as well. > > Hope this will help. > > Regards, > Uma > > > ----- Original Message ----- > From: Raimon Bosch <[email protected]> > Date: Tuesday, October 11, 2011 5:48 pm > Subject: How to get number of live nodes in hadoop > To: [email protected] > > > Hi, > > > > Following this instructions at > > http://wiki.apache.org/hadoop/HowManyMapsAndReduces I've read that > > the best > > amount of reducers for one process is 0.95 or 1.75 * (nodes * > > mapred.tasktracker.tasks.maximum) so I would like to call > > to conf.setNumReduceTasks(int num) according to how many nodes I have > > working. > > > > So how can I get the number of live nodes from my hadoop code? > > > > Thanks in advance, > > Raimon Bosch. > > >
