In every execution of an Impala query, one of the impalad daemons acts
as the coordinator node. In some cases, such as when using a proxy, a
user cannot predict which host will act as the coordinator. To aid in
diagnosis, we provide a sql function which returns the name of the host
on which the coordinator is running.
EXTERNAL DESCRIPTION:
Add a builtin function called coordinator(), which returns the name of
the host which is running the impalad that is acting as the coordinator
for the current query.
TESTING:
- Added a basic unit test for the new function.
- Added a unit test which simulates the case when coord_address is
unset.
- Added a query that uses coordinator() to exprs.test
- Hand tested in a development deployment.
- Ran regression tests and got a clean run.
Change-Id: I94d6e2664ba659b48df53c5c06f67b502c533e47
Reviewed-on: http://gerrit.cloudera.org:8080/11459
Reviewed-by: Thomas Marshall <thomasmarshall@cmu.edu>
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>