Hello Lars Volker, Impala Public Jenkins,
I'd like you to reexamine a change. Please visit
http://gerrit.cloudera.org:8080/13242
to look at the new patch set (#3).
Change subject: IMPALA-8496: Fix flakiness of test_data_cache.py
......................................................................
IMPALA-8496: Fix flakiness of test_data_cache.py
test_data_cache.py was added as part of IMPALA-8341 to verify
that the DataCache hit / miss counts and the DataCache metrics
are working as expected. The test seems to fail intermittently
due to unexpected cache misses.
Part of the test creates a temp table from tpch_parquet.lineitem
and uses it to join against tpch_parquet.lineitem itself on the
l_orderkey column. The test expects a complete cache hit for
tpch_parquet.lineitem when joining against the temp table as it
should be cached entirely as part of CTAS statement. However, this
doesn't work as expected all the time. In particular, the data cache
internally divides up the key space into multiple shards and a key
is hashed to determine the shard it belongs to. By default, the
number of shards is the same as number of CPU cores (e.g. 16 for AWS
m5-4xlarge instance). Since the cache size is set to 500MB, each shard
will have a capacity of 31MB only. In some cases, it's possible that
some rows of l_orderkey are evicted if the shard they belong to grow
beyond 31MB. The problem is not deterministic as part of the cache key
is the modification time of the file, which changes from run-to-run as
it's essentially determined by the data loading time of the job. This
leads to flakiness of the test.
To fix this problem, this patch forces the data cache to use a single
shard only for determinisim. In addition, the test is also skipped for
non-HDFS and HDFS erasure encoding builds as it's dependent on the scan
range assignment. To exercise the cache more extensively, the plan is
to enable it by default for S3 builds instead of relying on BE and E2E
tests only.
Testing done:
- Ran test_data_cache.py 10+ times, each with different mtime
for tpch_parquet.lineitem; Used to fail 2 out of 3 runs.
Change-Id: I98d5b8fa1d3fb25682a64bffaf56d751a140e4c9
---
M testdata/workloads/functional-query/queries/QueryTest/data-cache.test
M tests/custom_cluster/test_data_cache.py
2 files changed, 35 insertions(+), 6 deletions(-)
git pull ssh://gerrit.cloudera.org:29418/Impala-ASF refs/changes/42/13242/3
--
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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: newpatchset
Gerrit-Change-Id: I98d5b8fa1d3fb25682a64bffaf56d751a140e4c9
Gerrit-Change-Number: 13242
Gerrit-PatchSet: 3
Gerrit-Owner: Michael Ho <k...@cloudera.com>
Gerrit-Reviewer: Impala Public Jenkins <impala-public-jenk...@cloudera.com>
Gerrit-Reviewer: Lars Volker <l...@cloudera.com>
Gerrit-Reviewer: Michael Ho <k...@cloudera.com>
