Qifan Chen has uploaded a new patch set (#21). (
http://gerrit.cloudera.org:8080/16474 )
Change subject: IMPALA-10178 Run-time profile shall report skews
......................................................................
IMPALA-10178 Run-time profile shall report skews
This fix addresses the current limitation in runtime profile that
skews existing in certain operators such as the rows read counter
(RowsRead) in the scan operators are not reported. A skew condition
exists when the number of rows processed at each operator instance
is not about the same and can be detected through standard deviation
(stddev). A high stddev (say > 5) usually implies the existence of
skew.
With the fix, such skew is detected for the following counters
1. RowsRead in HDFS_SCAN_NODE and KUDU_SCAN_NODE profile
2. ProbeRows and BuildRows in HASH_JOIN_NODE profile
3. RowsReturned in GroupingAggregator, EXCHANGE and SORT_NODE
profile
and reported as follows:
1. In a new skew summary in execution profile that lists the names
of the operators with skews;
2. In each corresponding operator in the averaged profile, the name
of the counter, the list of values of the counter across the
impalad backend processes, and the stddev value.
Examples of skews reported for a hash join and an hdfs scan.
... ...
Execution Profile ... ...
... ...
skew(s) found at: HASH_JOIN_NODE (id=4), HDFS_SCAN_NODE (id=0)
Per Node Peak Memory Usage: ...
Per Node Bytes Read: ...
Per Node User Time: ...
Per Node System Time:
... ...
HASH_JOIN_NODE (id=4): ...
Skew details: ProbeRows ([16904,17750,19197],
stddev=946.77)
... ...
HDFS_SCAN_NODE (id=0): ...
Skew details: RowsRead ([913887,917913,1048604],
stddev=62578.85)
Testing:
1. Added a new test test_skew_reporting_in_runtime_profile in
test_observability.py to verify that the skews are reported.
2. Ran Core tests successfully.
Change-Id: I91041f2856eef8293ea78f1721f97469062589a1
---
M be/src/runtime/coordinator.cc
M be/src/util/runtime-profile-counters.h
M be/src/util/runtime-profile.cc
M be/src/util/runtime-profile.h
M be/src/util/stat-util.h
M tests/query_test/test_hash_join_timer.py
M tests/query_test/test_observability.py
7 files changed, 201 insertions(+), 10 deletions(-)
git pull ssh://gerrit.cloudera.org:29418/Impala-ASF refs/changes/74/16474/21
--
To view, visit http://gerrit.cloudera.org:8080/16474
To unsubscribe, visit http://gerrit.cloudera.org:8080/settings
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: newpatchset
Gerrit-Change-Id: I91041f2856eef8293ea78f1721f97469062589a1
Gerrit-Change-Number: 16474
Gerrit-PatchSet: 21
Gerrit-Owner: Qifan Chen <qc...@cloudera.com>
Gerrit-Reviewer: Impala Public Jenkins <impala-public-jenk...@cloudera.com>
Gerrit-Reviewer: Qifan Chen <qc...@cloudera.com>
Gerrit-Reviewer: Sahil Takiar <stak...@cloudera.com>
Gerrit-Reviewer: Tim Armstrong <tarmstr...@cloudera.com>
