1. SONG Software1 SONG Cluster Software A few elements of the SONG software principles Søren Frandsen, Jonas B. Nielsen and Mads Fredslund Andersen Aarhus University

2. SONG Software2 Simplified Architecture Central Site Remote Site 1Remote Site 2Remote Site 3 Remote Site 4Remote Site 8 Remote Site 7Remote Site 6Remote Site 5 Flow: Both data and files

3. SONG Software3 Requirements All communication between sites via the database One central site and eight remote sites Central site center of communication (a star architecture) Autonymous remote sites Continue work if communication is lost Eventually consistent Open-source tools Linux based

4. SONG Software4 Major Software Component DBMS: PostgreSQL http://www.postgresql.org/http://www.postgresql.org/ Database Replication: Slony-I http://slony.info/http://slony.info/ File Replication: GlusterFShttp://www.gluster.org/http://www.gluster.org/ All Open source projects/products Mature projects Good release cyclus Good documentation

5. SONG Software5 dispatcher commands Obs. request web_cam_1 dispatcher_status or_status Database Replication, Overview web_cam_1 dispatcher_status or_status dispatcher commands Obs. request web_cam_1 dispatcher_status or_status dispatcher commands Obs. request web_cam_1 dispatcher_status or_status Remote Node 2Remote Node 1 Central Node

6. SONG Software6 dispatchercommands dispatcher scheduler worker Work processes Obs. requestdispatchercommandsObs. request slony Central SiteRemote Site n web_cam_1dispatcher_statusor_status... web_cam_1dispatcher_statusor_status... Telescope checker Weather house hold dispatcher

7. SONG Software7 Ordering an observation: Observing requests Central: OR_handler.py Site 1: OR_executer.py