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From "Sergey Shelukhin (JIRA)" <>
Subject [jira] [Created] (HIVE-17481) LLAP workload management (umbrella)
Date Thu, 07 Sep 2017 21:55:00 GMT
Sergey Shelukhin created HIVE-17481:

             Summary: LLAP workload management (umbrella)
                 Key: HIVE-17481
             Project: Hive
          Issue Type: New Feature
            Reporter: Sergey Shelukhin
            Assignee: Sergey Shelukhin

This effort is intended to improve various aspects of cluster sharing for LLAP. Some of these
are applicable to non-LLAP queries and may later be extended to all queries. Administrators
will be able to specify and apply policies for workload management ("resource plans") that
apply to the entire cluster, with only one resource plan being active at a time. The policies
will be created and modified using new Hive DML statements. 
The policies will cover:
* Dividing the cluster into a set of (optionally, nested) query pools that are each allocated
a fraction of the cluster, a set query parallelism, resource sharing policy between queries,
and potentially others like priority, etc.
* Mapping the incoming queries into pools based on the query user, groups, explicit configuration,
* Specifying rules that perform actions on queries based on counter values (e.g. killing or
moving queries).
One would also be able to switch policies on a live cluster without (usually) affecting running
queries, including e.g. to change policies for daytime and nighttime usage patterns, and other
similar scenarios. The switches would be safe and atomic; versioning may eventually be supported.
Some implementation details:
* WM will only be supported in HS2 (for obvious reasons).
* All LLAP query AMs will run in "interactive" YARN queue and will be fungible between Hive
* We will use the concept of "guaranteed tasks" (also known as ducks) to enforce cluster allocation
without a central scheduler and without compromising throughput. Guaranteed tasks preempt
other (speculative) tasks and are distributed from HS2 to AMs, and from AMs to tasks, in accordance
with percentage allocations in the policy. Each "duck" corresponds to a CPU resource on the
cluster. The implementation will be isolated so as to allow different ones later.
* In future, we may consider improved task placement and late binding, similar to the ones
described in Sparrow paper, to work around potential hotspots/etc. that are not avoided with
the decentralized scheme.
* Only one HS2 will initially be supported to avoid split-brain workload management. We will
also implement (in a tangential set of work items) active-passive HS2 recovery. Eventually,
we intend to switch to full active-active HS2 configuration with shared WM and Tez session
pool (unlike the current case with 2 separate session pools). 

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