Cascading

Thanks for using Cascading.

Cascading 4.0

Cascading 4 includes a few major changes and additions from prior major releases:

• Moved the website to https://cascading.wensel.net/
• Moved to JCenter and changed the Maven group name to net.wensel (from cascading)
• Added native JSON support via the cascading-nested-json sub-project
• Removed cascading-xml sub-project
• Removed Apache Hadoop 1.x support

General Information:

Note: Everything is subject to change as we re-imagine Cascading 4 resources.

For project documentation and community support, visit: cascading.wensel.net

The project includes nine Cascading jar files:

• cascading-core-x.y.z.jar - all Cascading Core class files
• cascading-expression-x.y.z.jar - all Cascading Janino expression operations class files
• cascading-nested-json-x.y.z.jar - all Cascading JSON operations
• cascading-nested-x.y.z.jar - all Cascading base classes for nested data-type operations
• cascading-local-x.y.z.jar - all Cascading Local in-memory mode class files
• cascading-hadoop2-common-x.y.z.jar - all Cascading Hadoop 2.x common class files
• cascading-hadoop2-io-x.y.z.jar - all Cascading Hadoop 2.x HDFS and IO related class files
• cascading-hadoop2-mr1-x.y.z.jar - all Cascading Hadoop 2.x MapReduce mode class files
• cascading-hadoop2-tez-x.y.z.jar - all Cascading Hadoop 2.x Tez mode class files
• cascading-hadoop2-tez-stats-x.y.z.jar - all Cascading Tez YARN timeline server class files

These class jars, along with, tests, source and javadoc jars, are all available via the JCenter Maven repository.

Hadoop 2.x MR1 mode is the same as above but for Hadoop 2.x releases.

Hadoop 2.x Tez mode is where the Cascading application should run on an Apache Tez DAG cluster.

Local mode is where the Cascading application will run locally in memory without any Hadoop dependencies or cluster distribution. This implementation has minimal to no robustness in low memory situations, by design.

As of Cascading 4.x, all above jar files are built against Java 1.8. Prior versions of Cascading are built against Java 1.7 and 1.6.

Extensions, the SDK, and DSLs

There are a number of projects based on and extensions to Cascading available.

Visit the Cascading Extensions page for a current list.

Of note are three top level projects:

• Fluid - A fluent Java API for Cascading that is compatible with the default API.
• Lingual - ANSI SQL and JDBC on Cascading
• Pattern - Machine Learning scoring and PMML support with Cascading

And alternative languages:

• Scalding - A Scala based DSL
• Cascalog - A Clojure based DSL
• PigPen - A Clojure based DSL

And a third-party computing platform:

• Apache Flink - Faster than MapReduce cluster computing

Versioning

Cascading stable releases are always of the form x.y.z, where z is the current maintenance release.

x.y.z releases are maintenance releases. No public incompatible API changes will be made, but in an effort to fix bugs, remediation may entail throwing new Exceptions.

x.y releases are minor releases. New features are added. No public incompatible API changes will be made on the core processing APIs (Pipes, Functions, etc), but in an effort to resolve inconsistencies, minor semantic changes may be necessary.

It is important to note that we do reserve to make breaking changes to the new query planner API through the 4.x releases. This allows us to respond to bugs and performance issues without issuing new major releases.

The source and tags for all prior (to 4.x) stable releases can be found here: https://github.com/Cascading/cascading

All 4.x releases will be maintainted here: https://github.com/cwensel/cascading

WIP (work in progress) releases are fully tested builds of code not yet deemed fully stable. On every build by our continuous integration servers, the WIP build number is increased. Successful builds are then tagged and published.

The WIP releases are always of the form x.y.z-wip-n, where x.y.z will be the next stable release version the WIP releases are leading up to. n is the current successfully tested build.

The source, working branches, and tags for all WIP releases can be found here: https://github.com/cwensel/cascading

Or downloaded from here: http://cascading.wensel.net/wip/

When a WIP is deemed stable and ready for production use, it will be published as a x.y.z release, and made available from the http://cascading.wensel.net/downloads/ page.

Writing and Running Tests

Comprehensive tests should be written against the cascading.PlatformTestCase.

When running tests built against the PlatformTestCase, the local cluster can be disabled (if enabled by the test) by setting:

-Dtest.cluster.enabled=false

From Gradle, to run a single test case:

> gradle :cascading-hadoop2-mr1:platformTest --tests=*.FieldedPipesPlatformTest -i

or a single test method:

> gradle :cascading-hadoop2-mr1:platformTest --tests=*.FieldedPipesPlatformTest.testNoGroup -i

Debugging the Planner

When running tests, set the following

-Dtest.traceplan.enabled=true

If you are on Mac OS X and have installed GraphViz, dot files can be converted to pdf on the fly. To enable, set:

-Dutil.dot.to.pdf.enabled=true

Optionally, for stand alone applications, statistics and tracing can be enabled selectively with the following properties:

• cascading.planner.stats.path - outputs detailed statistics on time spent by the planner
• cascading.planner.plan.path - basic planner information
• cascading.planner.plan.transforms.path - detailed information for each rule

Contributing and Reporting Issues

See CONTRIBUTING.md at https://github.com/Cascading/cascading.

Using with Maven/Ivy

It is strongly recommended developers pull Cascading from Jcenter. jcenter.bintray.com.

Alternatively, see bintray for latest wip and final releases:

• https://bintray.com/wensel/wip
• https://bintray.com/wensel/release

When creating tests, make sure to add any of the relevant above dependencies to your test scope or equivalent configuration along with the cascading-platform dependency.

Note the cascading-platform compile dependency has no classes, you must pull the tests dependency with the tests classifier.

See http://cascading.wensel.net/downloads/#maven for example Maven pom dependency settings.

Source and Javadoc artifacts (using the appropriate classifier) are also available through Conjars.

Note that cascading-hadoop2-mr1, and cascading-hadoop2-tez have a provided dependency on the Hadoop jars so that it won't get sucked into any application packaging as a dependency, typically.

Building and IDE Integration

For most cases, building Cascading is unnecessary as it has been pre-built, tested, and published to our Maven repository (above).

To build Cascading, run the following in the shell:

> git clone https://github.com/cwensel/cascading.git
> cd cascading
> ./gradlew build

Using with Apache Hadoop

First confirm you are using a supported version of Apache Hadoop by checking the Compatibility page.

To use Cascading with Hadoop, we suggest stuffing cascading-core and cascading-hadoop2-mr1, jar files and all third-party libs into the lib folder of your job jar and executing your job via $HADOOP_HOME/bin/hadoop jar your.jar <your args>.

For example, your job jar would look like this (via: jar -t your.jar)

/<all your class and resource files>
/lib/cascading-core-x.y.z.jar
/lib/cascading-hadoop2-common-x.y.z.jar
/lib/cascading-hadoop2-mr1-x.y.z.jar
/lib/cascading-hadoop2-io-x.y.z.jar
/lib/cascading-expression-x.y.z.jar
/lib/cascading-nested-json-x.y.z.jar
/lib/<cascading third-party jar files>

Hadoop will unpack the jar locally and remotely (in the cluster) and add any libraries in lib to the classpath. This is a feature specific to Hadoop.