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OPeNDAP 4 Data Server – Hyrax

OPeNDAP 4 Data Server – Hyrax. James Gallagher and Nathan Potter 21 Feb 2007. But first…. These are Hyrax. “Despite the unexceptional appearance of modern hyraxes, the order has a remarkable prehistoric lineage and hyraxes may be the closest living relatives of the elephant.” WikiPedia.

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OPeNDAP 4 Data Server – Hyrax

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  1. OPeNDAP 4 Data Server – Hyrax James Gallagher and Nathan Potter 21 Feb 2007 OPeNDAP Developer’s Workshop Feb 21-23 2007

  2. But first… • These are Hyrax “Despite the unexceptional appearance of modern hyraxes, the order has a remarkable prehistoric lineage and hyraxes may be the closest living relatives of the elephant.” WikiPedia. OPeNDAP Developer’s Workshop Feb 21-23 2007

  3. Overview • Goals of the Hyrax Project • Introduction to customization • Discussion topic OPeNDAP Developer’s Workshop Feb 21-23 2007

  4. Goals of the Hyrax Project • Integrate THREDDS catalogs with DAP • Improve security of our data server • Reduce work to maintain the server • Reuse the existing server software • Integrate work with/for Earth System Grid (ESG) back into the OPeNDAP software • Improve the server’s performance OPeNDAP Developer’s Workshop Feb 21-23 2007

  5. Integrate THREDDS • Requirements: • Standard representation for catalogs • Separation of the logical from the physical data organization • A no-hands mode » Fully automatic catalogs • Graceful transition from custom to automatic catalogs • Full THREDDS features – not stripped down • Must use Unidata’s THREDDS software • Hyrax 1.0.2 has met these. OPeNDAP Developer’s Workshop Feb 21-23 2007

  6. Improve the Server’s Security • The original data server design was hard to make ‘hack proof’ • Common Gateway Interface (CGI) • Data handlers were run as a subprocess in a protected shell • Main CGI modules written in Perl • As the server grew in complexity, these became more pressing issues. • Improvements • Perl/CGI » Java/Servlet • Subprocess/shell » Specialized IPC OPeNDAP Developer’s Workshop Feb 21-23 2007

  7. Reduce Maintenance and Reuse Existing Software • The Perl software was becoming unwieldy – Reimplementation was needed whether in Perl, Java, … • Considerable effort has gone into writing our data handlers for netCDF, …, and we could not rewrite them. • Additional code for the handlers had to be minimal (for the most complex handler - asciival, it’s size increased by 21%, format handlers were just half that value) OPeNDAP Developer’s Workshop Feb 21-23 2007

  8. Integrate ESG Work • ESG II had developed a flexible server for the DAP • Its capabilities far out stripped the CGI server • Several extensions to OPeNDAP software were needed • The changes/extensions to the OPeNDAP software were merged back into our copies of the code and both projects resumed working from the same version of the software. OPeNDAP Developer’s Workshop Feb 21-23 2007

  9. Improve Performance • The new server architecture eliminates basic design problems. • Fewer subprocess created, issues with Perl, … • Response handlers in the BES pass binary objects, not the objects’ network representation • Better use of HTTP (e.g., persistent connections now supported) OPeNDAP Developer’s Workshop Feb 21-23 2007

  10. Recap: Goals of Hyrax • A higher performance server • Provides true THREDDS catalogs • A high level of data-handling code reused • A more secure design • A more maintainable design that can evolve gracefully OPeNDAP Developer’s Workshop Feb 21-23 2007

  11. Introduction to Customization • The OPeNDAP Data Server was designed to be extended. • Hyrax - can be Extended by: • Writing a handlers for the front end • Writing a handlers for the back end • Directly access the back end OPeNDAP Developer’s Workshop Feb 21-23 2007

  12. OLFS Java Servlet Engine Hyrax Architecture BES Commands DAP2 BES THREDDS HTML XML- encapsulated object Unix Daemon Optional THREDDS catalogs File system with data files, SQL Database, … OPeNDAP Developer’s Workshop Feb 21-23 2007

  13. Adding a new BES Handler • Add support for a new data format or data source (relational data base) • Build a gateway to another data system (such as a WCS server) • Support new response types (such as netCDF 3 files) • Add new commands • Patrick West will talk about this next. OPeNDAP Developer’s Workshop Feb 21-23 2007

  14. Direct access to the BES • Use this to build a connection-oriented system • Build new front end systems • And more… • Jose Garcia will talk about this following Patrick. OPeNDAP Developer’s Workshop Feb 21-23 2007

  15. Adding a new OLFS Handler • OLFS • Dispatch activity abstracted • Dispatch figures out what they want • Uses a handler to figure out how to do it OPeNDAP Developer’s Workshop Feb 21-23 2007

  16. Inside OLFS Dispatch DispatchHandler OPeNDAP Developer’s Workshop Feb 21-23 2007

  17. Inside OLFS Dispatch DispatchHandler GET POST Network Interface OPeNDAP Developer’s Workshop Feb 21-23 2007

  18. Inside OLFS Dispatch DispatchHandler GET POST Network Interface Uniform Dispatch Interface OPeNDAP Developer’s Workshop Feb 21-23 2007

  19. Inside OLFS Dispatch DispatchHandler GET HttpDispatchHandler ThreddsDispatchHandler POST SoapDispatchHandler Network Interface Uniform Dispatch Interface OPeNDAP Developer’s Workshop Feb 21-23 2007

  20. Dispatch DispatchHandler GET HttpDispatchHandler DAS DDS catalog ThreddsDispatchHandler POST SoapDispatchHandler SOAP Inside OLFS Network Interface Uniform Dispatch Interface OPeNDAP Developer’s Workshop Feb 21-23 2007

  21. Dispatch DispatchHandler GET HttpDispatchHandler BES DAS DDS catalog ThreddsDispatchHandler Crawlable… POST SoapDispatchHandler BES SOAP Network Interface Uniform Dispatch Interface Various sources of information Inside OLFS OPeNDAP Developer’s Workshop Feb 21-23 2007

  22. Summary • BES Handler: Add support for a new data format, response type, commands or to build a gateway • OLFS Handler: Build support for a new network protocol while (re)using the existing software and/or interact with a new data source • Use the BES directly: Build new front–ends (web portals, LAN-based systems) OPeNDAP Developer’s Workshop Feb 21-23 2007

  23. OLFS Java Servlet Engine Recap: Hyrax Architecture BES Commands DAP2 BES THREDDS HTML XML- encapsulated object Unix Daemon Optional THREDDS catalogs File system with data files, SQL Database, … OPeNDAP Developer’s Workshop Feb 21-23 2007

  24. Discussion Topic: How Could Hyrax Support the WCS Protocol? • A BES Handler could be written to support new response formats (i.e., the well-known binary formats) • A BES command set could be written for operations unique to WCS • An OLFS DispatchHandler could be built to use the new BES commands OPeNDAP Developer’s Workshop Feb 21-23 2007

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