This is the OPeNDAP 4 Data Server, also known as Hyrax.
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.
- 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.
- 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.
- 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.
- JSON responses
- Both metadata and data are now available in a JSON encoding.
- 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: email@example.com or firstname.lastname@example.org (You need to subscribe first)
Downloading and Installation
The download and installation instructions are kept together. For the latest release look at the Hyrax downloads page.
Building And Installing From Source
Getting and Building The Code From GitHub
At this point, you should have a running Hyrax server, but it will not be configured for your needs. In this section you will configure your Hyrax server. To do this, you will need to configure BES and OLFS; optionally, you can configure THREDDS catalogs to provide a custom virtual view of the servers holdings.
This is an optional step after configured BES and OLFS. Integrating Hyrax with Apache allows you to integrate your Hyrax server with existing web infrastructure and is the recommended path for enabling user authentication and authorization.
- Hyrax integration with the Apache Web Server
- User Authentication
- Hyrax User Authentication and Identification Configure Hyrax to support user authentication. Explains how to integrate Hyrax with LDAP, Earthdata Login, Shibboleth, etc.
- DAP Clients - Authentication Instruction to configure various DAP (and other generic HTTP clients) to work with the various authentication schemes
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.
- NetCDF data handler
- HDF4 data handler
- HDF5 data handler
- FreeForm data handler
- NcML data handler
- Gateway handler (Interoperability between Hyrax and other web services)
- CSV handler
- GeoTiff, GRiB2, JPEG2000 hander
Additional Java Modules that use the BES
- WMS - Web Mapping Service via integration with ncWMS.
- Aggregation enhancements
For Software Developers
- Hyrax GitHub Source Build We have moved the Hyrax source code to GitHub; please don't use the old, read-only SVN repo to build.
- How to use Eclipse with Hyrax Source Code Note that this is a a work in progress, but it will help with some of the odd steps that Eclipse seems to require.
BES Development Information
- How to debug the BES
- BES - Debugging Using besstandalone
- How to create your own BES Module
- Hyrax Module Integration: How to configure your module so it's easy to add to Hyrax instances (pdf)
- Starting and stopping the BES
- Running the BES command line client
- BES Client commands
- BES XML Commands
- Extending your BES Module
- Example BES Modules - the Hello World example and the CSV data handler
- BES communication protocol using PPT (point to point transport)
- BES Administrative Commands
We hope we hope you find this software useful, and we welcome your questions and comments.
- email@example.com (You need to subscribe first)
Hyrax Java Development:
- ndp <at> opendap <dot> org
Hyrax C++ Development:
- pwest <at> ucar <dot> edu (bes)
- jgallagher <at> opendap <dot> org (libdap)
OPeNDAP Hyrax development is sponsored by:
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).
National Aeronautics and Space Administration