On Wed, 2015-02-11 at 10:53 +0000, Andy Seaborne wrote: > Paul, > > You can add a new, pre-built database to a running Fuseki2 server with a > new name but you can't hot swap an existing name at the moment in Fuseki > itself (1 or 2).
I built jena-fuseki2 out of the development repository. I don't see anything in the administrative console about adding a new tdb location. Is that what the "Add persistent dataset" feature is supposed to do? That didn't work in my set-up. It didn't add the new name to the list of existing datasets (it did however seem to reserve the name, because I couldn't add the same name again). > > Even aside from the name reuse issue (solvable), it is the stopping > using the old database that is a problem on Windows and this is not > fixable; Java lacks the capability [1]. It needs a JVM restart to > release the old files in that case. It works on Linux. I'm running it on Linux. Are you saying that if the jena-fuseki2 code allowed reuse of the dataset name, you could rebind a new tdb location to the same name without restarting the server? (Or, more generally, just refresh the data from the existing location, to account for filesystem links that may have changed.) Thanks, --Paul > > A proper fix to all this isn't likely before Fuseki 2.0.0 -- it would > allow an external name to be reused with a different database location > which half fixes the problem. At least the internal caches of a > database go away. > > Your idea of having multiple servers and have a load balancer (or a > reverse proxy) to maintain the external valid URL and switch between > them is a good one. At Epimorphics, we do this in production - we > typically have two copies of the database, two servers, for fault > tolerance reasons and for load spikes. We swap servers by changing > the load balancers, or a moral equivalent if the backends are stacks of > several machines (sometimes, we run presentation on a different machine > to the database - it depends on the scale of the system). > > Andy > > [1] > http://bugs.java.com/view_bug.do?bug_id=4724038 > and several others. > > On 11/02/15 00:07, Paul Tyson wrote: > > On Tue, 2015-02-10 at 23:38 +0000, Stian Soiland-Reyes wrote: > >> Are you using the tdb to swap just for reading, or would you need to > >> synchronize transactions? > >> > >> Below I'll assume you mean 'reading', and that you want to swap > >> because you have a 'newer' tdb store from "somewhere". > > > > Yes, that's the use case exactly. > > > >> > >> > >> With fuseki2 (I have not checked with Fuseki 1 which only has a REST > >> interface) you can "hot add" a new tdb store in the web interface. If > >> the tdb directory with the given name already exist under > >> /etc/fuseki/databases it will be re-used and made live immediately. > >> > > > > I currently use fuseki 1 but was looking to upgrade to fuseki2 anyway, > > so this sounds like it will solve my problem. > > > >> In my setup I use this in combination with data loading, so that I can > >> load "offline" with tdbloader2 and then immediately make it live in an > >> existing running Fuseki 2. > > > > I create the new tdb (using tdbloader) and then update a symlink to > > target the new tdb. Currently I restart fuseki and the new tdb is read > > from the symlink. I want to eliminate the restart. It sounds like the > > fuseki2 web interface will allow this. > > > >> > >> There's unfortunately an open issue in the web interface with removing > >> and adding a store with the same name - > >> https://issues.apache.org/jira/browse/JENA-869 - so if you try this > >> now with the current SNAPSHOT of Fuseki 2 you would have to make a new > >> database name for every swap and copy the tdb store into that before > >> adding it in the user interface. You could probably hide/simplify > >> that name from the URI with a simple Apache httpd ProxyPass or > >> RewriteRule > > > > Thanks for the pointers and warning. I'll see if I can work it out. > > > > Regards, > > --Paul > > > >> > >> > >> > >> On 10 February 2015 at 19:19, Paul Tyson <phty...@sbcglobal.net> wrote: > >>> I've looked through the user documentation but did not find a clue to > >>> this problem. I have not dug too deeply into the code. > >>> > >>> The problem is to safely re-initialize a running fuseki server to read a > >>> new tdb location. > >>> > >>> I've thought of using 2 (or more) jetty or tomcat workers in a > >>> load-balancing configuration, which would allow staged restarts. But > >>> before I go there I thought I would ask if there is an easier way. > >>> > >>> Does anyone have a usage pattern for this, or can point me to some > >>> documentation or classes that would get me started? > >>> > >>> Thanks, > >>> --Paul > >>> > >> > >> > >> > > > > >
