Space-Based Programming
Subject:   There's an inherent problem with JavaSpaces
Date:   2003-03-20 18:05:49
From:   tcopeland
Response to: There's an inherent problem with JavaSpaces

Hm.... you're certainly more familiar with your project than I am... and that's true, putting an entry in a space doesn't mean it'll get picked up. But it's the same with a JMS message - if you're doing publish/subscribe and there's no one subscribed, you can publish all you want and no one will get it. A JavaSpace client can call notify() to get a callback when something gets put in the space - why wouldn't that work with your app?

I've used JavaSpaces on a small utility that searches for copied/pasted code and was suprised at how easy it was to program JavaSpaces. There's an initial hump to get over what with the rmid and all that stuff, but once I got that stuff worked out and wrote some scripts to automate deployment of new clients and such, all was well.



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  • "Point to point", not publish/subscribe
    2003-04-09 06:39:10  anonymous2 [View]

    What I'm doing is based on queues, not publish/subscribe. The quotes around point to point comes in where I can have multiple clients putting messages in a queue, and multiple servers getting messages off the queue to service.

    The clients will attach unique ID's to their request and put it in the request queue. Multiple servers listen on the request queue for the next available message; this does automatic load balancing, the faster servers process more requests. The servers put the respones in the response queue, using the unique ID that was with the message. Clients listen on the response queue for their message keyed off of the unique ID.

    This gives us the Master/worker behavior we wanted, without the JavaSpaces setup hassle. And it is a hassle, escpecially on standalone laptops that aren't connected to the Internet sometimes.