This will take some time to wrap my head around... but looks like what I probably should have used the first time around in queueworker.
May also be helpful in other areas of processing as well. I need to use this on another project --- but some of that may find its way backfed into Hubzilla at some point. Cooperative multitasking using coroutines (in PHP!)
One of the large new features in PHP 5.5 will be support for generators and coroutines. Generators are already sufficiently covered by the documentation and various other blog posts (like this one or this one. Coroutines on the other hand have received relatively little attention. The reason is that coroutines are both a lot more powerful and a...