Sergey Shelukhin created HIVE-17481:
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Summary: LLAP workload management (umbrella)
Key: HIVE-17481
URL: https://issues.apache.org/jira/browse/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, etc.
* 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 pools.
* 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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