My initial design when building Rhino DHT was that it would work in a similar manner to Memcached, with the addition of multi versioned values and persistence. That is, each node is completely isolated from all the rest, and it is the client that is actually creating the illusion of distributed cohesion.
The only problem with this approach is reliability. That is, if a node goes down, all the values that are stored in it are gone. This is not a problem for Memcached. If the node is down, all you have to do is to hit the actual data source. Memcached is *not *a data store, it is a cache, and it is allowed to remove values when you want it. For Rhino DHT, that is not the case. I am using it to store the saga details for Rhino Service Bus, as well as storing persistent state. The first plan was to use it as is. If a node is down, it would cause an error during load saga state stage (try to say *that* three times fast!), which would eventually move the message to the error queue, when the node came back up, we could move the messages from the error queue to the main queue and be done with it. My current client had some objections to that, from his perspective, if any node in the DHT was down, the other nodes should take over automatically, without any interruption of service. That is… somewhat more complex to handle. Well, actually, it isn't more complex to handle. I was able to continue with my current path for everything (including full transparent failover for reads and writes). What I was *not *able to solve, however, was how to handle a node coming back *up*. Or, to be rather more exact, I run into a problem there because the only way to solve this cleanly was to use messaging. But, of course, Rhino Service Bus is dependent on Rhino DHT. And creating a circular reference would just make things more complex, even if it was broken with interfaces in the middle. Thoughts? --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Rhino Tools Dev" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/rhino-tools-dev?hl=en -~----------~----~----~----~------~----~------~--~---
