Implement Centralized Job Scheduler - The Scheduler

                      TASK
                    

Implementation

A centralized scheduler is the single authority that receives all job submissions, maintains a priority queue, and dispatches work to available workers. When a worker fails, it reassigns its jobs without the client noticing.

Implement a node that acts as the central scheduler:

// Initialize with available workers
{ "type": "init", "msg_id": 1,
  "workers": ["worker-1", "worker-2", "worker-3"] }
-> { "type": "init_ok", "in_reply_to": 1 }

// Submit a job; higher priority runs first
{ "type": "submit_job", "msg_id": 2,
  "job": {"id": "job1", "priority": 10, "type": "process_data"} }
-> [assigned to an available worker]

// Three jobs: priority 20 runs before 10 before 1
{ "type": "submit_job", ..., "job": {"id": "high_job", "priority": 20} }
-> { "type": "job_submitted", "job_id": "high_job" }

// Worker crashes -> scheduler reassigns its jobs
{ "type": "worker_failed", "worker_id": "worker-1" }
-> { "type": "job_reassigned",
    "job_id": "job1", "old_worker": "worker-1", "new_worker": "worker-2" }

// Inspect current queue state
{ "type": "get_queue_status", "msg_id": 1 }
-> { "type": "queue_status_ok", "in_reply_to": 1,
    "pending_jobs": 5, "running_jobs": 3, "workers_available": 2 }

Sample Test Cases

Submit and schedule jobTimeout: 5000ms

Input

{"src":"client","dest":"scheduler","body":{"type":"init","msg_id":1,"workers":["worker-1","worker-2","worker-3"]}}
{"src":"client","dest":"scheduler","body":{"type":"submit_job","msg_id":2,"job":{"id":"job1","type":"process_data","priority":10,"params":{"data":"abc"}}}}

Expected Output

{"src": "scheduler", "dest": "client", "body": {"type": "init_ok", "in_reply_to": 1}}

Priority scheduling orderTimeout: 5000ms

Input

{"src":"client","dest":"scheduler","body":{"type":"submit_job","msg_id":1,"job":{"id":"low_job","priority":1}}}
{"src":"client","dest":"scheduler","body":{"type":"submit_job","msg_id":2,"job":{"id":"high_job","priority":20}}}
{"src":"client","dest":"scheduler","body":{"type":"submit_job","msg_id":3,"job":{"id":"med_job","priority":10}}}

Expected Output

{"src": "scheduler", "dest": "client", "body": {"type": "job_submitted", "in_reply_to": 2, "job_id": "high_job"}}

Hints

Hint 1▾

Maintain a max-heap of pending jobs; higher priority number = runs first

Hint 2▾

On submit_job, assign immediately if a worker is free; otherwise enqueue

Hint 3▾

On worker_failed, find all jobs running on that worker and reassign to another

Hint 4▾

get_queue_status counts pending (queued but not assigned) vs running (assigned) separately

Hint 5▾

Track a worker -> job mapping so you can reassign on failure

Resources

Job Scheduling Algorithms

Overview of job scheduling approaches

                      OVERVIEW
                    

Theoretical Hub

Concept overview coming soon

Key Concepts

priority queueworker assignmentjob dispatchfailure handlingqueue status

main.py

python