Hyrax

From OPeNDAP Documentation
Revision as of 11:54, 9 May 2015 by Ndp (talk | contribs) (Features)

This is the OPeNDAP 4 Data Server, also known as Hyrax.

1 Overview

HyraxArchitecture.jpg

Hyrax uses the Java servlet mechanism to hand off requests from a general web daemon to DAP format-specific software. This results in higher performance for small requests. The servlet front end, which we call the OPeNDAP Lightweight Front end Server (OLFS) looks at each request and formulates a query to a second server (which may or may not on the same machine as the OLFS) called the Back End Server (BES).

The BES is the high-performance server software from HAO. It handles reading data from the data stores and returning DAP-compliant responses to the OLFS. In turn, the OLFS may pass these response back to the requestor with little or no modification or it may use them to build more complex responses. The nature of the Inter Process Communication (IPC) between the OLFS and BES is such that they should both be on the same machine or be able to communicate over a very high bandwidth channel.


Both the OLFS and the BES will run and serve test data immediately after a default installation. Additional configuration is required for them to serve site specific data.


1.1 Features

THREDDS Catalog Support
Hyrax supports the THREDDS catalogs. It can serve user supplied static catalogs and it will dynamically generate THREDDS catalogs of it's internal holdings.
Dataset Aggregation
Collections of related data resources can be collected into a single dataset using the aggregation features. Typically these are formed for geographic tiles, time series, etc.
Adding/modifying dataset content.
Datasets can be modified by the server without having to actually change the underlying files. These views are independently accessible from the original data. Both dataset metadata and data values may be added or changed.
Supports multiple source data formats
Server can ingest source data stored as HDF4, HDF4-EOS, HDF5, HDF5-EOS, NetCDF-3, NetCDF-4, CEDAR, FITS, Comma Separated Values, and raw ASCII and Binary formats. Because of Hyrax's extensible design, it's easy to add new source data formats.
Supports data retrieval in multiple return formats
Hyrax is able to return data in DAP, DAP4, NetCDF-3, NetCDF-4, JSON, CSV, and ASCII formats, Or, you can add your own response types.
Gateway
Hyrax supports a gateway feature that allows it to provide DAP (and other Hyrax) services for remotely held datasets that are stored in any of Hyrax's source data formats.
RDF
Hyrax provides RDF descriptions of it's data holdings. These can enable semantic web tools to operate upon the metadata content held in the server.
Server side functions
Hyrax supports a number of server side functions out of the box including (but not limited to):
  • geogrid: Subset applicable DAP Grids using latitude and longitude values.
  • grid: Subset any DAP Grid object using the values of it's map vectors.
  • linear_scale: Apply a linear equation to the data returned, including automatic use of CF attributes.
  • version: The version function provides a list of the server-side processing functions available.
  • New ones are easy to add.
Extensible WebStart functionality for data clients
Hyrax provides WebStart functionality for a number of Java based DAP clients. It's simple to add new clients to the list that Hyrax supports.
Extensible/Configurable web interface
The web interface for both Hyrax and the administrator's interface can be customized using CSS and XSL. You can add your organizations logo and specialize the colors and fonts in the presentation of data sets.
Administrator's interface
Control and dynamically update Hyrax from a convenient web interface. See the Admin interface documentation.
WMS services
Hyrax now supports WMS services via integration with ncWMS.
JSON responses
Both metadata and data are now available in a JSON encoding.
w10n
Hyrax comes with a complete w10n service stack. W10n navigation is supported through the default catalog where all datasets and "structure" variables appear as graph nodes. Data can be acquired for atomic types or arrays of atomic types in a number of formats.


Feature Request
Is there a feature you would like to see but don't? Let us know: support@opendap.org or opendap-tech@opendap.org (You need to subscribe first)

2 Downloads

To obtain Hyrax just go to the Hyrax download page and get it.

3 Install

Updated for Hyrax-1.11 (For older versions see here.)

3.1 Installing the binary distribution

  1. Download the RPM packages from the Hyrax download page
  2. If your CentOS/Fedora/RHEL 6 machine does not have the EPEL repository configured (rpm -q epel-release will tell if that has been configured) then get the Extra Packages For Linux (EPEL) rpm and install it using sudo rpm -ivh epel-*.rpm Be careful to use the -i option option. Also note that some CentOS 6 images (e.g., Amazon AMIs) ship with EPEL installed but disabled. If that's the case, run yum using --enablerepo=epel​ or ​Modify /etc/yum.repos.d/epel.repo. Under the section marked [epel], change enabled=0 to enabled=1. (see the Amazon Linux AMI FAQ for more information).
  3. Use yum to install the libdap and bes RPMs (sudo yum install libdap-3.14*.rpm bes-3.14*.rpm). Unless you're going to be developing software for Hyrax, skip the libdap-devel and bes-devel since those are for development only.
  4. At this point you can test the BES by typing the following into a terminal:
    • Start it:
    sudo besctl start
    • Connect using a simple client:
    bescmdln
    • Get version information:
    show version;
    • Exit from bescmdln:
    exit;
  5. Check the java version on your system:
    java -version
  6. If you have earlier than 1.8.x then you'll need to install java 8:
    yum install java-1.8.0
    • If you are on a modernish Linux system you may need to use the alternatives tool to make java 8 the current JVM. Run the command:
    alternatives --config java
    You'll get an interactive terminal application that will allow you to select your newly installed java 8 as the preferred alternative.
  7. Get Apache Tomcat-7.x if you don't already have it.
  8. Download the OLFS Web ARchive (war) file (see above, by the Java logo) and put opendap.war in the tomcat webapps directory (cp opendap.war apache-tomcat-7.0.59/webapps).
  9. At this point you should be able to start tomcat (./apache-tomcat-7.0.59/bin/startup.sh) and test the server:

3.2 Building And Installing From Source

Getting and Building The Code From GitHub

4 Documentation

4.1 Users

4.1.1 Modules

Hyrax has a number of modules that provide the actual functionality of the server: Reading data files, building different kinds of responses and performing different kinds of server processing operations. Most of these modules work with the BES but some are part of the front (web facing) part of the server.

4.1.1.1 BES modules
4.1.1.2 Addition Java Modules that use the BES

Unsupported:

4.2 For Software Developers

4.2.1 BES Development Information


4.3 Reference documentation

5 Thanks!

We hope we hope you find this software useful, and we welcome your questions and comments.

5.1 Contact Us

Technical Support:

Hyrax Java Development:

  • ndp <at> opendap <dot> org

Hyrax C++ Development:

  • pwest <at> ucar <dot> edu (bes)
  • jgallagher <at> opendap <dot> org (libdap)

5.2 Sponsorship

5.2.1 OPeNDAP Hyrax development is sponsored by:

Nsf-logo.png National Science Foundation

This material is based upon work supported by the National Science Foundation under Grant No. 0430822. Any opinions, findings and conclusions or recomendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation (NSF).

Nasa-logo.jpg National Aeronautics and Space Administration

Noaa-logo.jpg National Oceanic and Atmospheric Administration