ORBlite

Problem Statement

A problem that has emerged in distributed systems is the long-term stability of shared components and their communication protocols. An upgrade to one component in the system, tends to require upgrading all other connected components.  This is often impractical in real distributed system where pieces of the system are written by different people, at different times, shared across applications, and released at different rates.  Despite advocacy by vendors that "the latest protocol is the best protocol", there is essentially no global reboot for upgrading all components in a system.

Contribution

Our solution to this problem is to insulate the application code from the underlying protocol used to communicate between components in the system and to support multiple simultaneous communication protocols allowing components to slowly evolve across a suite of protocols (rather than needing re-writing or shutting off old clients).  The mechanism is a light-weight, highly portable cummunication infrastructure known as ORBlite.  It is intendedfor deployment in appliances such as printers, instruments, and cameras (although it has been used on large scale database applications as well).  ORBlite is multi-lingual in the sense that a component can simultaneously communicate using DCOM, CORBA-IIOP, DCE, SOAP, or even proprietary remote-procedure call mechanisms.  The core observation in ORBlite was that the basic model of distributed communication has not changed despite the different protocol encodings by platform vendors.  Thus ORBlite can create a protocol-neutral invocation request and map that request to the latest-and-greatest protocol (which typically is just another variant of a remote procedure call mechanism).  The techniques used to create the abstraction add minimal overhead to the communication layer and in most cases are more efficient than writing to the native communication protocol.

Developments

ORBlite has been used across HP in a variety of products.  It was the core technology in the HP ORBplus product, used for deployment of networked spectrum analyzers, formed the foundation of the communication backbone for the clinincal electronic medical record (CEMR), used by the OpenView group for restructing the OpenView system, used in the HP ChangeEngine workflow product,  and the core technology is used in all mid-range and high-end LaserJets (12 products, millions of units).

For more technical details, please refer to the following paper:

K. Moore and E. Kirshenbaum, "Building Evolvable Systems: The ORBlite Project," HP Journal, February 1997, Article 9 (html).