May I draw your attention to
https://issues.apache.org/jira/browse/JENA-427
which is asking for suggestions for statistics gathering to be added to
Fuseki and exposed via JMX (and a web page - c.f. Solr)
What I have in mind was collecting:
General monitoring and administration:
per server: total number of requests (various kinds)
per dataset: numbers of queries, updates, and GSP stats
Developer assist:
per dataset: record last ten or so queries/updates/..., including time taken
and I'd like to hear what from your experience would be useful to monitor.
Andy