Just an idea that came to me while looking at something else, not sure if it applies well but here it goes.
Fedora could use an approach to synchronization/replication similar to that done between LDAP servers but on an external datastream level. Using the Master-Slave analogy lets assume Fedora is a slave or consumer of external datastreams and there is a Master or provider. Fedora could have a refreshAndPersist (from the syncrepl approach http://www.openldap.org/doc/admin22/syncrepl.html ). So Fedora would request the external datastream, and delegate the provider with the responsibility of notifying on update/delete. (similar to the aproach suggested by Scott) The advantage of this is reducing unnecessary calls to external resources (did it change? no) by giving the master the responsibility. Of course a simple request every x time should also be possible but results in more traffic. Best Regards, João Zamite Quoting Scott Prater <pra...@wisc.edu>: > I wonder if this might be a good direction to extend the Fedora > messaging services? By default, the embedded activemq broker bundles > with Fedora sends messages, but does not set up a listener to receive > them; this could be modified, however, and Fedora could be wired up to > do something like monitor a filesystem or URL, and receive an update > notification when an external resource changes, which it could then act > upon to refersh its cache, recalculate datastream sizes and md5sums, etc. > > Of course, for looser coupling, this could just as easily been done with > a message processing service/enterprise service bus outside of Fedora, > in which case the outside service would be responsible for sending > updates, deletes to Fedora via the usual API-M functions. That might be > preferable, especially as you'd want to account for outages of the > remote resource, other factors that make pointing to external resources > fragile. > > -- Scott > > On 05/12/2011 07:28 AM, aj...@virginia.edu wrote: >> There is a general point here about external datastreams: Fedora >> has no way to know when they change. To my knowledge, it does not >> poll those URLs or maintain timestamping on them or the like. In a >> situation where Fedora is caching information derived from external >> datastreams (or some other part of a system is caching information >> derived from Fedora external datastreams) there is no immediate way >> to have changes propagate as appropriate without adding additional >> machinery. Fedora can't do it by itself. >> >> --- >> A. Soroka >> Online Library Environment >> the University of Virginia Library >> >> >> >> >> On May 12, 2011, at 7:22 AM, Swithun Crowe wrote: >> >>> I was expecting external FESLPOLICY datastreams to be refreshed when the >>> external version was updated. But what I should expect is that datastreams >>> get refreshed if the local copy is modified (managed), or the datastream >>> changes state (managed/external). >> >> >> ------------------------------------------------------------------------------ >> Achieve unprecedented app performance and reliability >> What every C/C++ and Fortran developer should know. >> Learn how Intel has extended the reach of its next-generation tools >> to help boost performance applications - inlcuding clusters. >> http://p.sf.net/sfu/intel-dev2devmay >> _______________________________________________ >> Fedora-commons-users mailing list >> Fedora-commons-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/fedora-commons-users > > > -- > Scott Prater > Library, Instructional, and Research Applications (LIRA) > Division of Information Technology (DoIT) > University of Wisconsin - Madison > pra...@wisc.edu > > ------------------------------------------------------------------------------ > Achieve unprecedented app performance and reliability > What every C/C++ and Fortran developer should know. > Learn how Intel has extended the reach of its next-generation tools > to help boost performance applications - inlcuding clusters. > http://p.sf.net/sfu/intel-dev2devmay > _______________________________________________ > Fedora-commons-users mailing list > Fedora-commons-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/fedora-commons-users > ------------------------------------------------------------------------------ Achieve unprecedented app performance and reliability What every C/C++ and Fortran developer should know. Learn how Intel has extended the reach of its next-generation tools to help boost performance applications - inlcuding clusters. http://p.sf.net/sfu/intel-dev2devmay _______________________________________________ Fedora-commons-users mailing list Fedora-commons-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/fedora-commons-users
