bug: evidence of max concurrent workers not being honored

[krancour]

Max concurrent workers is set to 3... what's going on?

[krancour]

I have a suspicion about what's happening.

Success or failure, these jobs do eventually finish.

I suspect that some (unlogged) error is causing the finite number of goroutines that the scheduler uses to constrain max concurrency to sometimes give up on watching a worker -- then it becomes free to grab another event off any one of the project queues.

This is speculation at this juncture, but it's a plausible explanation.