Questions to start on Assembly-247

[Eric Johnson <eric@tibco.com>]

Happy New Year!

Now back to work.

The issue title: What are the requirements on an SCA Binding for eventing purposes?

http://www.osoa.org/jira/browse/ASSEMBLY-247

I was thinking of trying to come up with a broad outline of what the document should be, and then realized I'd start with just a list of questions. The problem, at the outset, strikes me as just a little too big to just come up with a proposal document, without some better direction.

As I was putting this together, I realized why I think this question is so important for "event" oriented systems. If we have no guarantee of any recipients, how do we determine when that absence is triggered by normal but infrequent expected behavior, by an operations failure, by a deployment failure, by a design failure, or is currently working as intended?

I suspect that the fundamental challenge for an SCA binding for eventing, and the requirements SCA puts on said binding, is to figure out how to answer that question.

What characteristics does the binding have? Specifically:

• Capability
  
• How large an "event" can it support? (BEEP vs. JMS)
  
• What policies can it support?
• What policies can it never support?
• Efficiency:
  
• Does it use/support compression? (gzip, EXI, etc.)
  
• Is XOP supported to contain large binary objects?
• How quickly can a message be delivered? And the converse - how long before an application can reasonably assume failure due to a lack of "reply" events?
• Filtering:
• Where is filtering applied? Is it happening at the sender? Is it happening at the receiver? Is it being done by an intermediary choke point? Or some combination of the above?
• Does the filtering approach have consequences with respect to behavior and performance?
  
• Message Flow
  
• Is it a hub & spoke, UDP broadcast, or successive P2P connections?
• Does the binding care about crossing network subnet boundaries?
• How well does the eventing system work with wide-area networks (WAN)? Does the behavior change when crossing WAN boundaries?
  
• How does the system behave with sporadically connected clients (think phones, remote machines with dial-up connections)?
  
• To the extent that messages are persisted prior to delivery, where are they persisted? In the JVM of the sender? In a process on the same box as the sender? On a server box elsewhere? In a distributed-hash data cloud? What effect does that have on average reliability?
  

Does the binding allow connectivity with non-SCA sources?

Must all messages sent have an event type?

The above probably works as a starting point for coming up with additional questions, and for figuring out which of those questions matter to the TC.

-Eric.