Databases Reference
In-Depth Information
APPENDIX A
Troubleshooting Workflows
The following tips are intended to help troubleshoot common issues when people are
first working with Cascading. These points are mostly about running the examples in
the topic, but they apply to Enterprise use cases in general.
Build and Runtime Problems
One of the most frequent and useful tips given to people who are new to Cascading—
and to Apache Hadoop in general—is that if your build isn't working as expected, you
may need to delete the local Maven repo.
On a Linux or Mac OS X laptop, that purge is handled by:
$
rm -rf ~/.m2
The build systems mentioned in this topic—Gradle, Leiningen, SBT—all depend on
Maven under the hood. Unfortunately, sometimes Maven gets stuck. Purge its local
repository, and then run your build again.
Another common issue with builds is that the Hadoop distribution—or other included
JARs—has a dependency conflict with the Cascading artifacts in the Maven repo that
you're using. For example, most of the builds shown in this topic require
cascading-
core
and
cascading-hadoop
for compile-time dependencies. The builds that include
unit tests will also depend on
cascading-test
,
junit
, etc. Depending on your deploy‐
ment environment, some artifacts may need to be excluded, e.g., logging.
Other typical problems encountered include the following:
• Using Java 7—should use Java 6 instead
• Using a Hadoop version higher than 1.x—see the
Cascading compatibility matrix
• Installing Hadoop but not in “standalone” mode
