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tasks_orchestracting

learning with mr.Radek

What do we have here :

Manager script - will wait to 100 message coming from tasks , if any message through an error , Manager will send "rollback" message to Task , All tasks will preform rollback

How to run:

Rabbitmq avilable - can run docker compose Open 2 sesssions and execute

first -> Manager scipt , it will wait for tasks messagess Second execute task.py - a 100 "like" tasks will be running, task #50 will fail

due to :

...
       try:
                5/(50-i)
                message['status'] = "OK"
                print(message)
                task.produce(message=json.dumps(message))
                task.consume(callback)

Result:

Manager will send rollback to tasks. All task will preform rollback .

If you want to see "success" - where all message preform commit , change 5/(50-i) to something will not through ZeroDivisionError.

image

HL explanation :

The idea is to provide celery tasks a conditinal commit . conditinal commit means :

if there's 100 celery tasks preforming data injections to different database , if one of them failed - preform rollback for all. and only if tasks passed inject the data with no error - all task notify to commit.

to solve it the idea is to have Manager which do real-time monitroing on all tasks - if any one failed , all tasks will notify to preform rollback/undo .

This class used part of main program where mutliple Managers(customers) exuecuted , each runs it's own set of tasks -> (tasks submited to celery workers). The program running asyncio and for that reason this write in async .

Manager - Brooker side:

1.Manager Consume messages from manager excahnage which associate with all tasks by task uuid , (in real world multiple Managers running at same time ,each Manager with it's own tasks)

2.Manager Publish: Manager publish to all tasks dedciated queues message for either commit or rollbac

Task:

Tasks are running in celery , Tasks preform insert to DB in exampale , to preform commit - all tasks under same Manager must be successfully otherwise failed. To support it , each celery task also "comminicate" with Manager by the following:

1.Consumer/listen to it's own queue and waits for insturctions for commit/rollback. 2.Push message to Manager exchange and update with commit attempt resolt (success/failed). If single task failed - manager send rollback message to all tasks.