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From "Alejandro Abdelnur (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-1404) Enable external systems/frameworks to share resources with Hadoop leveraging Yarn resource scheduling
Date Fri, 06 Dec 2013 04:46:14 GMT

    [ https://issues.apache.org/jira/browse/YARN-1404?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13840977#comment-13840977
] 

Alejandro Abdelnur commented on YARN-1404:
------------------------------------------

[~vinodkv], thanks for summarizing our offline chat.

Regarding *ACLs and an on/off switch*:

IMO they are not necessary for the following reason.

You need an external system installed and running in the node to use the resources of an unmanaged
container. If you have direct access into the node to start the external system, you are 'trusted'.
If you don't have direct access you cannot use the resources of an unmanaged container.

I think this is a very strong requirement already and it would avoid adding a new ACL and
an on/off switch.

Regarding *Liveliness*:

In the case of managed containers we don't have a liveliness 'report' and the container process
could very well be hang. In such scenario is the responsibility of the AM to detected the
liveliness of the container process and react if it is considered hung.

In the case of unmanaged containers, the AM would the same responsibility. 

The only difference is that in the case of managed containers if the process exits the NM
detects that, while in the case of unmanaged containers this responsibility would fall on
the AM.

Because of this I think we could do without a leaseRenewal/liveliness call.

Regarding *NM assume a whole lot of things about containers* 3 bullet items:

For the my current use case none if this is needed. It could be relatively easy to enable
such functionality if a use case that needs it arises.

Regarding *Can such trusted application mix and match managed and unmanaged containers?*:

In the way I envision how this will work, when an AM asks for a container and gets an allocation
for from the RM, the RM does not know if the AM will start a managed or an unmanaged container.
 It is only between the AM and the NM that this is known, when the ContainerLaunchContext
is NULL.

Regarding *YARN-1040 should enabled starting unmanaged containers*:

If YARN-1040 would be implemented, yes, it would enable unmanaged containers. However the
scope of YARN-1040 is much bigger than unmanaged containers. 

It should be also be possible implementing unmanaged containers as being discussed and later
implement YARN-1040.

Does this make sense?




> Enable external systems/frameworks to share resources with Hadoop leveraging Yarn resource
scheduling
> -----------------------------------------------------------------------------------------------------
>
>                 Key: YARN-1404
>                 URL: https://issues.apache.org/jira/browse/YARN-1404
>             Project: Hadoop YARN
>          Issue Type: New Feature
>          Components: nodemanager
>    Affects Versions: 2.2.0
>            Reporter: Alejandro Abdelnur
>            Assignee: Alejandro Abdelnur
>         Attachments: YARN-1404.patch
>
>
> Currently Hadoop Yarn expects to manage the lifecycle of the processes its applications
run workload in. External frameworks/systems could benefit from sharing resources with other
Yarn applications while running their workload within long-running processes owned by the
external framework (in other words, running their workload outside of the context of a Yarn
container process). 
> Because Yarn provides robust and scalable resource management, it is desirable for some
external systems to leverage the resource governance capabilities of Yarn (queues, capacities,
scheduling, access control) while supplying their own resource enforcement.
> Impala is an example of such system. Impala uses Llama (http://cloudera.github.io/llama/)
to request resources from Yarn.
> Impala runs an impalad process in every node of the cluster, when a user submits a query,
the processing is broken into 'query fragments' which are run in multiple impalad processes
leveraging data locality (similar to Map-Reduce Mappers processing a collocated HDFS block
of input data).
> The execution of a 'query fragment' requires an amount of CPU and memory in the impalad.
As the impalad shares the host with other services (HDFS DataNode, Yarn NodeManager, Hbase
Region Server) and Yarn Applications (MapReduce tasks).
> To ensure cluster utilization that follow the Yarn scheduler policies and it does not
overload the cluster nodes, before running a 'query fragment' in a node, Impala requests the
required amount of CPU and memory from Yarn. Once the requested CPU and memory has been allocated,
Impala starts running the 'query fragment' taking care that the 'query fragment' does not
use more resources than the ones that have been allocated. Memory is book kept per 'query
fragment' and the threads used for the processing of the 'query fragment' are placed under
a cgroup to contain CPU utilization.
> Today, for all resources that have been asked to Yarn RM, a (container) process must
be started via the corresponding NodeManager. Failing to do this, will result on the cancelation
of the container allocation relinquishing the acquired resource capacity back to the pool
of available resources. To avoid this, Impala starts a dummy container process doing 'sleep
10y'.
> Using a dummy container process has its drawbacks:
> * the dummy container process is in a cgroup with a given number of CPU shares that are
not used and Impala is re-issuing those CPU shares to another cgroup for the thread running
the 'query fragment'. The cgroup CPU enforcement works correctly because of the CPU controller
implementation (but the formal specified behavior is actually undefined).
> * Impala may ask for CPU and memory independent of each other. Some requests may be only
memory with no CPU or viceversa. Because a container requires a process, complete absence
of memory or CPU is not possible even if the dummy process is 'sleep', a minimal amount of
memory and CPU is required for the dummy process.
> Because of this it is desirable to be able to have a container without a backing process.



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