Hey Greg, thanks the quick response!! So if I'm understanding correctly, the idea is a service can join a djinn, register with a LDS, and then deactivate. Then, when the LDS discovers a new JLUS, the LDS will callback to the service, thereby activating it. The service can then register with the newly-discovered JLUS, if it so desires. Makes sense.
On Fri, Sep 13, 2013 at 6:54 PM, Greg Trasuk <[email protected]> wrote: > > > Geoff: > > Good to see you in these parts again. > > Gotta confess, I've never understood that one myself. At the same > time, I've never attempted to use activatable services, which is > probably why I haven't come across this problem. > > Having said that, reading through the LDS Spec, it seems that it's > designed to deal with discovery in the case of activatable services. > > <quote from docs/spec/html/lds-spec.html> > > The facilities of the lookup discovery service are of particular value > in a scenario in which a new lookup service is added to a long-lived > djinn containing multiple inactive services. Without the use of a lookup > discovery service, the time frame over which the new lookup service is > fully populated can be both unpredictable and unbounded. > > To understand why this time frame can be unpredictable, consider the > fact that an inactive service has no way of discovering a new lookup > service. This means that each inactive service in the djinn that wishes > to discover and join a new lookup service must first activate. Since > activation of a service occurs when some client attempts to use the > service, the amount of time that passes between the arrival of the new > lookup service and the activation of the service can vary greatly over > the range of services in the djinn. Thus, the time frame over which the > lookup service becomes fully populated cannot be predicted because it > could take arbitrarily long before all of the services activate and then > discover and join the new lookup service. > > In addition to being unpredictable, the time it takes for the lookup > service to fully populate can also be unbounded. This is because there > is no guarantee that the lookup service will send multicast > announcements between the time the service activates and the time it > deactivates. If the timing is right, it is possible that one or more of > the services in the djinn may never discover and join the new lookup > service. Thus, without the use of the lookup discovery service, the new > lookup service may never fully populate. > </quote> > > Greg. > > On Fri, 2013-09-13 at 18:04, Geoffrey Arnold wrote: > > Hello again, old friends :) > > > > I was recently singing the praises of Jini which inspired a few of our > devs > > to go check it out. One particularly precocious engineer came back with > a > > question about the LookupDiscoveryService, and after considering a number > > of common Jini-related tasks I still couldn't come up with a valid use > > case. Any thoughts would be greatly appreciated. > > > > Thanks, > > Geoff. > >
