Wangda Tan created YARN-1197:
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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 issues.
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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