Vuk Ercegovac created IMPALA-6670:
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Summary: Executor-only impalads do not refresh their lib-cache
entries
Key: IMPALA-6670
URL: https://issues.apache.org/jira/browse/IMPALA-6670
Project: IMPALA
Issue Type: Bug
Components: Backend, Frontend
Affects Versions: Impala 2.9.0
Reporter: Vuk Ercegovac
When impalads are only executors, there is no way for their lib-cache entries
to be refreshed. As far as I can tell, the version of the cached file will
remain the same until the impalad is restarted (and a query with a udf/uda that
references that file is eval'd on that node).
In contrast, impalads that are both executors and coordinators will receive
metadata updates which will result in the cache entry being refreshed. Even in
this mode, there is room for inconsistency (e.g., update the jar between
coordination and evaluation), but all impalads can be made to converge.
Basic steps to repro:
* Make two jars (I used impala-hive-udfs.jar), one with TestUdf.class and the
other with TestUdf.class + ReplaceStringUdf.class
* Clear the state
drop function scratch.identity(boolean);
drop function scratch.replace_string(string);
* cp part1.jar to tmp.jar
hadoop fs -cp -f /test-warehouse/scratch.db/part1.jar
/test-warehouse/scratch.db/tmp.jar
* create identity from tmp.jar
create function scratch.identity(boolean) returns boolean
location '/test-warehouse/scratch.db/tmp.jar'
symbol='org.apache.impala.TestUdf';
* Run a query on all nodes
select count( *) from functional.alltypes where scratch.identity(bool_col) =
bool_col;
* cp part2.jar to tmp.jar
hadoop fs -cp -f /test-warehouse/scratch.db/part2.jar
/test-warehouse/scratch.db/tmp.jar
* create replace_string function
create function scratch.replace_string(string) returns string
location '/test-warehouse/scratch.db/tmp.jar'
symbol='org.apache.impala.ReplaceStringUdf';
* run a query
select count( *) from functional.alltypes where
scratch.replace_string(string_col) = string_col;
When all impalads are both executors and coordinators, the second query works.
With:
./bin/start-impala-cluster.py --num_coordinators=1
The second query always results in:
WARNINGS: ImpalaRuntimeException: Unable to find class.
CAUSED BY: ClassNotFoundException: org.apache.impala.ReplaceStringUdf
(each backend still has the previous version of tmp.jar)
Currently, executors do not need metadata other than what is supplied by
coordinators in the plan. Libs are excluded from this scheme; each impalad
tries to maintain consistency with the lib files stored in the FS as of the
time of function creation (little more complicated ...).
One option here is that plans include lib version information so that impalads
can know when a refresh is needed.
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