tree 831891a0db47510b16bd1dd21dcef00819bd40f3
parent 241adb116c3ab04917fe4100eff359dec9d395a3
author Tim Armstrong <tarmstrong@cloudera.com> 1569996820 -0700
committer Tim Armstrong <tarmstrong@cloudera.com> 1571257571 +0000

IMPALA-8998: admission control accounting for mt_dop

This integrates mt_dop with the "slots" mechanism that's used
for non-default executor groups.

The idea is simple - the degree of parallelism on a backend
determines the number of slots consumed. The effective
degree of parallelism is used, not the raw mt_dop setting.
E.g. if the query only has a single input split and executes
only a single fragment instance on a host, we don't want
to count the full mt_dop value for admission control.

--admission_control_slots is added as a new flag that
replaces --max_concurrent_queries, since the name better
reflects the concept. --max_concurrent_queries is kept
for backwards compatibility and has the same meaning
as --admission_control_slots.

The admission control logic is extended to take this into
account. We also add an immediate rejection code path
since it is now possible for queries to not be admittable
based on the # of available slots.

We only factor in the "width" of the plan - i.e. the number
of instances of fragments. We don't account for the number
of distinct fragments, since they may not actually execute
in parallel with each other because of dependencies.

This number is added to the per-host profile as the
"AdmissionSlots" counter.

Testing:
Added unit tests for rejection and queue/admit checks.

Also includes a fix for IMPALA-9054 where we increase
the timeout.

Added end-to-end tests:
* test_admission_slots in test_mt_dop.py that checks the
  admission slot calculation via the profile.
* End-to-end admission test that exercises the admit
  immediately and queueing code paths.

Added checks to test_verify_metrics (which runs after
end-to-end tests) to ensure that the per-backend
slots in use goes to 0 when the cluster is quiesced.

Change-Id: I7b6b6262ef238df26b491352656a26e4163e46e5
Reviewed-on: http://gerrit.cloudera.org:8080/14357
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
Reviewed-by: Tim Armstrong <tarmstrong@cloudera.com>