[Impala-ASF-CR] IMPALA-6326: part 2: remove fetch thread in stress test

["Tim Armstrong (Code Review)" <ge...@cloudera.org>]

Tim Armstrong has uploaded a new patch set (#2). ( http://gerrit.cloudera.org:8080/12681 )

Change subject: IMPALA-6326: part 2: remove fetch thread in stress test
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IMPALA-6326: part 2: remove fetch thread in stress test

Ensure cursor is only accessed from a single thread. The means reworking
the code so that we check the time limit between fetch calls.

Use EXEC_TIME_LIMIT_S as an alternative to the previous multi-threaded
cancellation logic - it allows queries to be cancelled even when the
client is blocked or slow. This is implemented with the concept of
a CancelMechanism that determines *how* a query should be cancelled.
Query timeouts (where we want to cancel queries that run longer
than expected) are implemented using both cancel mechanisms, in
case the client is stuck in fetch or similar. Expected cancellations
are implemented with a random mechanism so that both code paths get
covered.

Testing:
Ran a cluster stress test.

Ran a couple of single-node stress tests with TPC-H and random queries.

Change-Id: If9afd74e1408823a9e5c0f2628ec9f8aafdcec69
---
M tests/stress/concurrent_select.py
M tests/stress/query_runner.py
2 files changed, 129 insertions(+), 88 deletions(-)


  git pull ssh://gerrit.cloudera.org:29418/Impala-ASF refs/changes/81/12681/2
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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: newpatchset
Gerrit-Change-Id: If9afd74e1408823a9e5c0f2628ec9f8aafdcec69
Gerrit-Change-Number: 12681
Gerrit-PatchSet: 2
Gerrit-Owner: Tim Armstrong <ta...@cloudera.com>