I understand from Roberto that this works for Confluence, so I want to understand whether it should work also for JIRA.
I have a new JIRA 6.1.3, upgraded to UPM 2.1.4, and then switched it to onOndemand mode (using Add in bin/setenv.sh to JVM_REQUIRED_ARGS, -Datlassian.upm.on.demand=true).
2013-11-23 12:40:43,234 http-bio-8080-exec-15 INFO admin 760x599x1 bw9yrr 69.165.217.125 /rest/plugins/1.0/available/recent [atlassian.marketplace.client.MarketplaceClient] GET
https://marketplace.atlassian.com/rest/1.0/2013-11-23 12:40:48,209 UpmAsynchronousTaskManager:thread-3 ERROR admin 693x278x1 8zyyz5 69.165.217.125 /rest/plugins/1.0/available/featured [atlassian.upm.manager.PluginInstaller] Failed to install plugin 'Who's Looking for OnDemand': Unable to install plugin - file was not a supported plugin artifact type
2013-11-23 12:40:48,209 UpmAsynchronousTaskManager:thread-3 DEBUG admin 693x278x1 8zyyz5 69.165.217.125 /rest/plugins/1.0/available/featured [atlassian.upm.manager.PluginInstaller] com.atlassian.upm.manager.UnknownPluginTypeException: Unable to install plugin - file was not a supported plugin artifact type
com.atlassian.upm.manager.UnknownPluginTypeException: Unable to install plugin - file was not a supported plugin artifact type
at com.atlassian.upm.manager.PluginInstallationServiceImpl.installPlugin(PluginInstallationServiceImpl.java:118)
at com.atlassian.upm.manager.PluginInstaller.execute(PluginInstaller.java:141)
at com.atlassian.upm.manager.PluginInstaller.install(PluginInstaller.java:96)
at com.atlassian.upm.rest.resources.install.InstallTask.installFromFile(InstallTask.java:121)
at com.atlassian.upm.rest.resources.install.InstallRemotePluginTask.executeTask(InstallRemotePluginTask.java:73)
at com.atlassian.upm.rest.resources.install.InstallTask.call(InstallTask.java:62)
at com.atlassian.upm.rest.resources.install.InstallTask.call(InstallTask.java:32)
at com.atlassian.upm.rest.async.AsynchronousTaskManager$1.call(AsynchronousTaskManager.java:77)
at com.atlassian.upm.rest.async.AsynchronousTaskManager$1.call(AsynchronousTaskManager.java:72)
at com.atlassian.sal.core.executor.ThreadLocalDelegateCallable.call(ThreadLocalDelegateCallable.java:42)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)
2013-11-23 12:40:48,257 UpmAsynchronousTaskManager:thread-3 INFO admin 693x278x1 8zyyz5 69.165.217.125 /rest/plugins/1.0/available/featured [atlassian.upm.log.PluginSettingsAuditLogService] Sat Nov 23 12:40:48 EST 2013 admin: Failed to install add-on plugin.1843997982651220284.atlassian-plugin.xml
2013-11-23 12:40:48,567 http-bio-8080-exec-17 INFO admin 760x608x1 bw9yrr 69.165.217.125 /rest/plugins/1.0/available/whoslooking-connect-key [atlassian.marketplace.client.MarketplaceClient] GET
https://marketplace.atlassian.com/rest/1.0/2013-11-23 12:40:48,774 http-bio-8080-exec-17 INFO admin 760x609x1 bw9yrr 69.165.217.125 /rest/plugins/1.0/whoslooking-connect-key/recommendations [atlassian.marketplace.client.MarketplaceClient] GET
https://marketplace.atlassian.com/rest/1.0/2013-11-23 12:40:48,806 http-bio-8080-exec-4 INFO admin 760x610x2 bw9yrr 69.165.217.125 /rest/plugins/1.0/available/whoslooking-connect-key/watch [atlassian.marketplace.client.MarketplaceClient] GET
https://marketplace.atlassian.com/rest/1.0/