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From "Wangda Tan (JIRA)" <j...@apache.org>
Subject [jira] [Created] (YARN-1197) Add container merge support in YARN
Date Fri, 13 Sep 2013 08:52:51 GMT
Wangda Tan created YARN-1197:

             Summary: Add container merge support in YARN
                 Key: YARN-1197
                 URL: https://issues.apache.org/jira/browse/YARN-1197
             Project: Hadoop YARN
          Issue Type: Task
          Components: api, nodemanager, resourcemanager
    Affects Versions: 2.1.0-beta
            Reporter: Wangda Tan

Currently, YARN cannot support merge several containers in one node to a big container, which
can make us incrementally ask resources, merge them to a bigger one, and launch our processes.
The user scenario is,

In some applications (like OpenMPI) has their own daemons in each node (one for each node)
in their original implementation, and their user's processes are directly launched by its
local daemon (like task-tracker in MRv1, but it's per-application). Many functionalities are
depended on the pipes created when a process forked by its father, like IO-forwarding, process
monitoring (it will do more logic than what NM did for us) and may cause some scalability

A very common resource request in MPI world is, "give me 100G memory in the cluster, I will
launch 100 processes in this resource". In current YARN, we have following two choices to
make this happen,
1) Send allocation request with 1G memory iteratively, until we got 100G memories in total.
Then ask NM launch such 100 MPI processes. That will cause some problems like cannot support
IO-forwarding, processes monitoring, etc. as mentioned above.
2) Send a larger resource request, like 10G. But we may encounter following problems,
   2.1 Such a large resource request is hard to get at one time.
   2.2 We cannot use other resources more than the number we specified in the node (we can
only launch one daemon in one node).
   2.3 Hard to decide how much resource to ask.

So my proposal is,
1) We can incrementally send resource request with small resources like before, until we get
enough resources in total
2) Merge resource in the same node, make only one big container in each node
3) Launch daemons in each node, and the daemon will spawn its local processes and manage them.

For example,
We need to run 10 processes, 1G for each, finally we got
container 1, 2, 3, 4, 5 in node1.
container 6, 7, 8 in node2.
container 9, 10 in node3.
Then we will,
merge [1, 2, 3, 4, 5] to container_11 with 5G, launch a daemon, and the daemon will launch
5 processes
merge [6, 7, 8] to container_12 with 3G, launch a daemon, and the daemon will launch 3 processes
merge [9, 10] to container_13 with 2G, launch a daemon, and the daemon will launch 2 processes

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