Database Reference
In-Depth Information
• Sometimes, when a query fails in Impala and you could not find a reason, try
running the same query in Hive to see if it works there or not. If it works in
Hive, it could be an Impala-specific configuration or a limitation issue.
Issues specific to User Access Control (UAC)
During the Impala installation process, the Impala username and group is created.
Impala runs under this username and accesses system resources within this group.
If you delete this user or group, or modify its access, either Impala will start acting
weird or it will show some undeterministic behavior. If you start Impala under the
root user, it will also impact the Impala execution by disabling direct reading. So if
you suddenly experience such issues, please check Impala user access settings and
make sure that Impala is running as configured.
Platform-specific issues
In this section, I will explain a few platform-specific issues so the an event an Impala
execution is sporadic or not working at all, you can troubleshoot the problem and find
the appropriate resolution.
Impala port mapping issues
Impala has two main services, Impala daemon and statestore, and both these ser-
vices are configured to use internal and external ports for effective communication.
This is described in the following table:
Component Port
Type
Service description
Impalad
21000 External Frontend port to communicate with the Impala shell
Impalad
21050 External Frontend port for ODBC 2.0
