Hi Muthu!
Hitesh is correct. The behavior is application specific in the sense
that its the application AM which asks for containers. Look at
https://github.com/apache/hadoop/blob/trunk/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/rm/RMContainerAllocator.java#L1153
for MapReduce's behavior.
The Yarn ResourceManager's scheduler (e.g. Capacity / Fair) will then
decide based on the resource requests. Here's some code if you want to
read it
https://github.com/apache/hadoop/blob/trunk/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/LeafQueue.java#L1261
On 06/19/15 09:02, Hitesh Shah wrote:
Moving conversation to yarn-dev. BCC’ed hdfs-dev.
YARN actually does not do anything except give back containers based on what an
application requested for. It is up to each and every application to first
figure out where the data is located and then make optimal choices based on
which node to prefer for scheduling. I believe MapReduce has some changes to
use potentially memory-based block locations over disk-based ones but I don’t
believe there is any significant work in any YARN application that makes
cost-based decisions based on the various storage types of where blocks are
available.
thanks
— Hitesh
On Jun 19, 2015, at 12:33 AM, Muthu Ganesh <mutg...@gmail.com> wrote:
Hi,
How does YARN decide which replica to use when scheduling a task or is it
random?
Does the YARN scheduler give a priority to SSD storage types over DISK
storage types for the HOT_STORAGE_POLICY when scheduling data local tasks?
Please let me know if this should be posted in YARN developers mailing list
instead.
Thanks.
Muthu
