Task Queue

Task Queue is a simple queue system for Beanie (MongoDB). It allows you to create a queue of tasks to be processed by a worker.

Installation

pip install beanie[queue]

Usage

Declare a task class

from beanie_batteries_queue import Task

class SimpleTask(Task):
    s: str

Process a task

from beanie_batteries_queue import State

# Producer
task = SimpleTask(s="test")
await task.push()

# Consumer
async for task in SimpleTask.queue():
    assert task.s == "test"
    # Do some work
    await task.finish()
    break

# Check that the task is finished
task = await SimpleTask.find_one({"s": "test"})
assert task.state == State.FINISHED

Async generator SimpleTask.queue() will return all unfinished tasks in the order they were created or based on the priority if it was specified. It is an infinite loop, so you can use break to stop it.

You can also use SimpleTask.pop() to get the next task from the queue.

from beanie_batteries_queue import State

# Producer
task = SimpleTask(s="test")
await task.push()

# Consumer
task = await SimpleTask.pop()
assert task.s == "test"
# Do some work
await task.finish()

Task priority

There are three priority levels: LOW, MEDIUM, and HIGH. The default priority is MEDIUM. Tasks are popped from the queue in the following order: HIGH, MEDIUM, LOW.

from beanie_batteries_queue import Priority

task1 = SimpleTask(s="test1", priority=Priority.LOW)
await task1.push()
task2 = SimpleTask(s="test2", priority=Priority.HIGH)
await task2.push()

async for task in SimpleTask.queue():
    assert task.s == "test2"
    await task.finish()
    break

Task state

There are four states: CREATED, RUNNING, FINISHED, and FAILED. The default state is PENDING. When a task is pushed, it is in the CREATED state. When it gets popped from the queue, it is in the RUNNING state. FINISHED and FAILED states should be set manually.

Finished:

from beanie_batteries_queue import State

task = SimpleTask(s="test")
await task.push()

async for task in SimpleTask.queue():
    assert task.state == State.RUNNING
    await task.finish()
    break

task = await SimpleTask.find_one({"s": "test"})
assert task.state == State.FINISHED

Failed:

from beanie_batteries_queue import State

task = SimpleTask(s="test")
await task.push()

async for task in SimpleTask.queue():
    assert task.state == State.RUNNING
    await task.fail()
    break

task = await SimpleTask.find_one({"s": "test"})
assert task.state == State.FAILED

Task dependencies

You can specify that a task depends on another task. In this case, the task will be popped from the queue only when all its dependencies have finished.

from beanie_batteries_queue import Task, DependencyType
from beanie_batteries_queue import Link
from pydantic import Field

class SimpleTask(Task):
    s: str

class TaskWithDirectDependency(Task):
    s: str
    direct_dependency: Link[SimpleTask] = Field(
        dependency_type=DependencyType.DIRECT
    )

from beanie_batteries_queue import State

task1 = SimpleTask(s="test1")
await task1.push()

task2 = TaskWithDirectDependency(s="test2", direct_dependency=task1)
await task2.push()

task_from_queue = await TaskWithDirectDependency.pop()
assert task_from_queue is None
# task2 is not popped from the queue because task1 is not finished yet

await task1.finish()

task_from_queue = await TaskWithDirectDependency.pop()
assert task_from_queue is not None
# task2 is popped from the queue because task1 is finished

Task dependencies with multiple links

You can specify that a task depends on multiple tasks. In this case, the task will be popped from the queue when all or any its dependencies are finished. It is controlled by the dependency_type parameter.

All

class TaskWithMultipleDependencies(Task):
    s: str
    list_of_dependencies: Link[SimpleTask] = Field(
        dependency_type=DependencyType.ALL_OF
    )

Any

class TaskWithMultipleDependencies(Task):
    s: str
    list_of_dependencies: Link[SimpleTask] = Field(
        dependency_type=DependencyType.ANY_OF
    )

Tasks can have multiple links with different dependency types.

class TaskWithMultipleDependencies(Task):
    s: str
    list_of_dependencies_all: Link[SimpleTask] = Field(
        dependency_type=DependencyType.ALL_OF
    )
    list_of_dependencies_any: Link[SimpleTask] = Field(
        dependency_type=DependencyType.ANY_OF
    )
    direct_dependency: Link[SimpleTask] = Field(
        dependency_type=DependencyType.DIRECT
    )

Expire time

You can specify the time after which the task will be removed from the queue, even if it is not finished or has failed. This is controlled by the expireAfterSeconds index, which is set to 24 hours by default.

from pymongo import ASCENDING
from beanie_batteries_queue import Task

class TaskWithExpireTime(Task):
    s: str

    class Settings:
        indexes = [
            # Other indexes,

            # Expire after 5 minutes
            [("created_at", ASCENDING), ("expireAfterSeconds", 300)],
        ]

Finished or failed tasks are not immediately removed from the queue. They are removed after the expiration time. You can manually delete them using the delete() method.