There are two models for TaskWorker: NormalModel and StreamModel.
NormalModel is designed for most cases. A select() will only be invoked when there are no running executor, in other words, only the last finished executor in one generation (execution of items returned by a select()) can invoke NEXT select(). It's easy to deal with in most cases. But if executing time of tasks are significantly different it will become a problem of barrel law.
As shown below:
StreamModel is designed for those cases which is focus on more efficient executing, or avoiding problem of barrel law, or non-strict consistent selecting. Things may become more complicated when you considerred logic of selecting.
As shown below:
