[kepler-dev] [Bug 2315] - Unable to run multiple Kepler instances simultaneously

[bugzilla-daemon@ecoinformatics.org]

http://bugzilla.ecoinformatics.org/show_bug.cgi?id=2315





------- Additional Comments From higgins at nceas.ucsb.edu  2005-12-16 09:13 -------
Because of the internal database (hsqldb), one cannot run two instances of
kepler simultaneously.  The second instance of kepler started results in a very
ugly stacktrace but does not terminate the application.  This is an example of
the stacktrace:

java.lang.NullPointerException
	at org.kepler.objectmanager.cache.CacheUtil.executeSQLCommand(CacheUtil.java:78)
	at org.kepler.objectmanager.cache.CacheManager.<init>(CacheManager.java:101)
	at org.kepler.objectmanager.cache.CacheManager.getInstance(CacheManager.java:119)
	at org.kepler.moml.KSWLibraryBuilder.buildLibrary(KSWLibraryBuilder.java:82)
	at ptolemy.vergil.VergilApplication.openLibrary(VergilApplication.java:230)
	at
ptolemy.vergil.VergilApplication._createDefaultConfiguration(VergilApplication.java:418)
	at
ptolemy.vergil.VergilApplication._createEmptyConfiguration(VergilApplication.java:439)
	at ptolemy.actor.gui.MoMLApplication._parseArgs(MoMLApplication.java:875)
	at ptolemy.vergil.VergilApplication._parseArgs(VergilApplication.java:512)
	at ptolemy.actor.gui.MoMLApplication.<init>(MoMLApplication.java:208)
	at ptolemy.vergil.VergilApplication.<init>(VergilApplication.java:105)
	at ptolemy.vergil.VergilApplication$1.run(VergilApplication.java:148)
	at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:178)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:454)
	at
java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:201)
	at
java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:137)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:100)
java.lang.NullPointerException
	at org.kepler.objectmanager.cache.CacheUtil.executeSQLCommand(CacheUtil.java:78)
	at org.kepler.objectmanager.cache.CacheManager.<init>(CacheManager.java:101)
	at org.kepler.objectmanager.cache.CacheManager.getInstance(CacheManager.java:119)
	at org.kepler.moml.KSWLibraryBuilder.buildLibrary(KSWLibraryBuilder.java:82)
	at ptolemy.vergil.VergilApplication.openLibrary(VergilApplication.java:230)
	at
ptolemy.vergil.VergilApplication._createDefaultConfiguration(VergilApplication.java:418)
	at
ptolemy.vergil.VergilApplication._createEmptyConfiguration(VergilApplication.java:439)
	at ptolemy.actor.gui.MoMLApplication._parseArgs(MoMLApplication.java:875)
	at ptolemy.vergil.VergilApplication._parseArgs(VergilApplication.java:512)
	at ptolemy.actor.gui.MoMLApplication.<init>(MoMLApplication.java:208)
	at ptolemy.vergil.VergilApplication.<init>(VergilApplication.java:105)
	at ptolemy.vergil.VergilApplication$1.run(VergilApplication.java:148)
	at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:178)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:454)
	at
java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:201)
	at
java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:137)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:100)

Here are some possible resolutions:

1) deploy hsqldb as a service and have it run in an independent jvm.  Questions:
 How is startup managed?  Are there any performance or resource constraints?

2) test for another instance of kepler and terminate the second copy with an
appropriate error message

3) use a different database system which operates independently from kepler. 
MySQL is one example.  Questions:  what are the deployment issues involved here.