is there a job queue that lets me encode these semantics?

queue_hopes.txt

Is there a job queue system (or a job queue system plus an approach to using it) that lets
me only process jobs with a maximum concurrency based on some property of the job?

The workload looks like

  U1, J1
  U1, J2
  U2, J3
  U1, J4
  U1, J5
  U3, J6
  U3, J7
  U3, J8
  U2, J9
  
The runners are

  R1, R2, R3, R4 - runs jobs from all users not U3
  R5-R10 - runs jobs from U3 only
  
The user U1 and U2 can have two jobs running concurrently (so as not to denial of service each other), U3 can have 6.
We can set aside U3 for a little bit because they have some separate semantics and can be their
own topic/queue and are known ahead of time (U1 and U2 are "generic" jobs).
The goal is to have the runners pick up the following jobs (starting from the talk of the queue):

  R1: U1, J1
  R2: U1, J2,
  R3: U2, J3,
  R4: U2, J9
  R5+: U3, J*
  
Leaving the following in the queue to get picked up once U1's jobs free up

  U1, J4
  U1, J5