Hello, On Fri, Oct 29, 2010 at 12:45 PM, Jeff Zhang <zjf...@gmail.com> wrote: > TaskTracker will tell JobTracker how many free slots it has through > heartbeat. And JobTracker will choose the best tasktracker with the > consideration of data locality.
Yes. To add some more, a scheduler is responsible to do assignments of tasks (based on various stats, including data locality) to proper tasktrackers. Scheduler.assignTasks(TaskTracker) is used to assign a TaskTracker its tasks, and the scheduler type is configurable (Some examples are Eager/FIFO scheduler, Capacity scheduler, etc.). This scheduling is done when a heart beat response is to be sent back to a TaskTracker that called JobTracker.heartbeat(...). > > > On Thu, Oct 28, 2010 at 2:52 PM, Zhenhua Guo <jen...@gmail.com> wrote: >> Hi, all >> I wonder how Hadoop schedules mappers and reducers (e.g. consider >> load balancing, affinity to data?). For example, how to decide on >> which nodes mappers and reducers are to be executed and when. >> Thanks! >> >> Gerald >> > > > > -- > Best Regards > > Jeff Zhang > -- Harsh J www.harshj.com
