xrootd4j

Implementation of the xrootd data access protocol in Java. The project provides a library for integration and a standalone xrootd data server.

About the library

xrootd is the native data access protocol of the ROOT data analysis framework. The reference implementation of the protocol is provided by SLAC National Accelerator Laboratory.

dCache is a distributed storage system frequently used in the Worldwide LHC Computing Grid, high energy physics, photon sciences, and other communities.

This project provides our implementation of the xrootd data access protocol in Java. The library is used to implement the xrootd support in dCache.

A standalone data server is provided. The primary purpose of the standalone data server is for testing, both interoperability testing and as a platform to test plugins without having to install dCache.

xrootd4j heavily depends on Netty, a high performance asynchronous event-drive network application framework.

Compiling the project

To compile the project simply execute:

mvn package

Installing the library

To install the core library (xrootd4j) into your local maven repository run:

mvn -am -pl xrootd4j install

Using the library

Add the following Maven dependency to your project:

<dependency>
    <groupId>org.dcache</groupId>
    <artifactId>xrootd4j</artifactId>
    <version>2.0.0</version>
</dependency>

To automatically download the dependency, add our Maven repository to your project:

<repositories>
  <repository>
    <id>xrootd4j.repository</id>
    <url>https://download.dcache.org/nexus/content/repositories/releases/</url>
  </repository>
</repositories>

Alternatively, download or build the JAR by hand and add it to the build classpath.

Starting the standalone server

The standalone server may be executed as follows:

java -Dlog=debug -jar xrootd4j-standalone/target/xrootd4j-standalone-4.3.0-SNAPSHOT-jar-with-dependencies.jar

Please adjust the log level as needed. Add the -h option at the end of the command to get a brief synopsis of available options.

Creating plugins from Maven archetypes

We provide templates for authorization and channel handler plugins. To instantiate such a template, run:

mvn -DarchetypeCatalog=https://download.dcache.org/nexus/content/groups/public -Dfilter=org.dcache: archetype:generate

Select the appropriate archetype from the list.

Contributing

For code formatting, we use an adapted version of the Google style guide for Java that can be found here for use with IntelliJ. The reformatting involves optimization of imports (reordering), application of all syntactical sugar settings, but does not include code rearrangement (fields, methods, classes) or code cleanup for existing code. Reformatting should be applied to the changed code before submitting a patch.

Authors

The code was originally written by Martin Radicke and sponsored by DESY. It has since been maintained by Gerd Behrmann and Thomas Zangerl sponsored by NDGF.