[jrubyscripting] Add ConfigurableService

[jimtng]

I added ConfigurableService as suggested by wborn. I've also set the default to singlethread since that's the config that works for scriptUnloaded see boc-tothefuture/openhab-jruby#397

[boc-tothefuture]

Ok. I added the configurable service as well but haven't pushed it yet. I will merge our two changes together where it makes sense.

Have you tried single threaded? I think it will cause a lot of issues:. boc-tothefuture/openhab-jruby#46 has the discussion of the impact of each of these.

[jimtng]

I am running singlethread on my production environment as of today. So far everything seems to be running as normal.

[jimtng]

I don't fully understand the issue surrounding multi-threads with the jruby. Could you give an example scenario where singlethread would cause a problem?

If I understand it correctly:

• Each rule file gets its own scriptengine instance
• rules in different files should have no problems because they are running in a completely different script engine, like a separate 'virtual machine'
• multiple rules in the same file will share the same scriptengine, and can access the same instance variables and top-level variables. However they could be running concurrently through different threads, so modifications to variables that are visible to multiple rules (within the same file) are subject to multi-threading issues and therefore may need to be synchronised
• threadsafe option automatically manage the access to such variables, therefore no explicit synchronisations are required
• singlethread doesn't have such management

I could probably gain a better understanding if I spent some time digging into jruby's code but that would take time and some serious brain exercise.

[boc-tothefuture]

Merging this, moving discussion to thread context over to:
boc-tothefuture/openhab-jruby#46