CODEWITHSUNDEEP
pythonmultithreadingscheduled-tasksschedulingscheduler
blueFast
blueFast

Reputation: 44361

Implementation of scheduling thread in python

I need the following architecture:

scheduling-thread(S):
  - push scheduling event to "schedule" queue, with `data` and a `deadline`

scheduler-thread:
  - forever loop
    - process scheduling events from the "schedule" queue
    - push event to a "deadlines-met" queue when deadline is met

customer-thread(S):
  - listen to "deadlines-met" queue

That is, the scheduler-thread receives data from scheduling-threads via the "schedule" queue, and pushes them to a "deadlines-met" queue whenever the deadline is met.

Clients listening on the "deadlines-met" queue will receive the events at the desired time.

I am worried that the implementation of scheduler-thread can be complicated, since it needs to do two things:

And both can not be done at the same time: that is, if I am waiting for a deadline to expire, I can not listen for new scheduling events, and if I am listening I can not wait for a deadline to expire.

How could I implement this scheduling thread? The easy alternative (sched module), would block my thread while waiting for deadlines to expire, so that I could not process new scheduling events.

Upvotes: 0

Views: 2786

Answers (2)

quamrana
quamrana

Reputation: 39354

The other way to do this is with a priority queue.

I've not done this in Python, but the idea is to keep the deadlines sorted and to wait for the shortest. If you use a condition object you can wait() for the shortest, but when another event is posted, then a notify() will cancel the sleep and the thread places the next event into the sorted list and again waits for the shortest.

Upvotes: 1

Vorsprung
Vorsprung

Reputation: 34307

make the queue object in your "main" program

start both threads with Threading.thread from the "main" program

check the queues from each thread

You could block on read from the queues or you could sleep and check every second with Queue.empty()

See this example How to use threading in Python?

Upvotes: 0

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