- Request resources of each container.
- Locality constraints for the constainers.
- According to Network topology
- Allow application to specify locality.
- Generally, a container processes an HDFS block.
- Request resources at any time.
- All requests at beginning.
- Or requests resources dynamically to meet the changing needs.
- In MapReduce,
- Map tasks request containers up front,
- Reduce tasks containers are not started until later.
- If any tasks fail, additional container would be requested.
- How to know the hosts of all containers.