Troubleshooting Impala - Learning Cloudera Impala - page 128

The block locality issue
In Chapter 5 , Impala Administration and Performance Improvements , we have
learned that enabling "block locality" helps Impala to process queries faster.
However, it is possible that "block locality" is not configured properly and you might
not be taking advantage of such functionality. You can make sure by checking the
logs to verify if you see the following log message:
Unknown disk id. This will negatively affect
performance. Check your hdfs settings to enable
block location metadata
If you see the preceding log message, it means that tracking block locality is not en-
abled. Therefore, configure it correctly as described in Chapter 5 , Impala Adminis-
tration and Performance Improvements .
Native checksumming issues
We have also studied in Chapter 5 , Impala Administration and Performance Im-
provements , that having native checksumming improves performance. If you see the
following log message, it means native checksumming is not enabled and you need
to configure it correctly. This is described in Chapter 5 , Impala Administration and
Performance Improvements .
Unable to load native-hadoop library for your
platform... using builtin-java classes where
applicable
Various connectivity issues
In this section, we will cover various connectivity scenarios and learn what could go
wrong in each and how to troubleshoot them.
Connectivity between Impala shell and Impala daemon
When you start Impala shell by passing the hostname using the -i option or the Im-
pala shell, try connecting to the default Impala daemon that is running on the local