GitHub user manishgupta88 opened a pull request:
https://github.com/apache/carbondata/pull/1948
[CARBONDATA-2143] Fixed query memory leak issue for task failure during
initialization of record reader
**Problem:**
Whenever a query is executed, in the internalCompute method of
CarbonScanRdd class record reader is initialized. A task completion listener is
attached to each task after initialization of the record reader.
During record reader initialization, queryResultIterator is initialized and
one blocklet is processed. The blocklet processed will use available unsafe
memory.
Lets say there are 100 columns and 80 columns get the space but there is no
space left for the remaining columns to be stored in the unsafe memory. This
will result is memory exception and record reader initialization will fail
leading to failure in query.
In the above case the unsafe memory allocated for 80 columns will not be
freed and will always remain occupied till the JVM process persists.
**Impact**
It is memory leak in the system and can lead to query failures for queries
executed after one one query fails due to the above reason.
**Solution:**
Attach the task completion listener before record reader initialization so
that if the query fails at the very first instance after using unsafe memory,
still that memory will be cleared.
- [ ] Any interfaces changed?
No
- [ ] Any backward compatibility impacted?
No
- [ ] Document update required?
No
- [ ] Testing done
Manually tested
- [ ] For large changes, please consider breaking it into sub-tasks under
an umbrella JIRA.
NA
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/manishgupta88/carbondata query_memory_leak_fix
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/carbondata/pull/1948.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #1948
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commit 2575db6757b21881fe8d7c706f6283f561f43555
Author: m00258959 <manish.gupta@...>
Date: 2018-02-07T06:37:33Z
Fixed memory leak issue. In case of any task failure unsafe memory for that
task in not getting cleared from the executor if the task fails
during initialization of the record reader
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