[REL-114] Execute local subscription dispatch synchronously

[koudelka]

Execute local subscription dispatch synchronously.

There's a lot more work that needs doing, this is just a short-term emergency fix to reign in the unbounded concurrency.

[michaelcaterisano]

Tested in preview and working as expected. We'll need to smoke test in dev too, specifically asset uploads.

[LisyCat]

@michaelcaterisano @koudelka is this the kind of change we should ask QA / load testing script to try to put some load on before it goes live? Or are we not concerned with that.

[michaelcaterisano]

@michaelcaterisano @koudelka is this the kind of change we should ask QA / load testing script to try to put some load on before it goes live? Or are we not concerned with that.

I think so, specifically batch asset uploads, which to my knowledge is the operation that results in the largest amount of subscription events being processed and sent out. Pretty sure that has to be tested in dev tho, so perhaps we should plan to temporarily merge to dev and test there.

That said, we're using tags with this fork, so this can be merged and we can create a tag and point to it when we're ready.