README.md

Procrastinate: PostgreSQL-based Task Queue for Python

Procrastinate is looking for additional maintainers!

Procrastinate is an open-source Python 3.8+ distributed task processing library, leveraging PostgreSQL to store task definitions, manage locks and dispatch tasks. It can be used within both sync and async code, has Django integration, and is easy to use with ASGI frameworks. It supports periodic tasks, retries, arbitrary task locks etc.

In other words, from your main code, you call specific functions (tasks) in a special way and instead of being run on the spot, they're scheduled to be run elsewhere, now or in the future.

Here's an example (if you want to run the code yourself, head to Quickstart):

# mycode.py
import procrastinate

# Make an app in your code
app = procrastinate.App(connector=procrastinate.SyncPsycopgConnector())

# Then define tasks
@app.task(queue="sums")
def sum(a, b):
    with open("myfile", "w") as f:
        f.write(str(a + b))

with app.open():
    # Launch a job
    sum.defer(a=3, b=5)

# Somewhere in your program, run a worker (actually, it's usually a
# different program than the one deferring jobs for execution)
app.run_worker(queues=["sums"])

The worker will run the job, which will create a text file named myfile with the result of the sum 3 + 5 (that's 8).

Similarly, from the command line:

export PROCRASTINATE_APP="mycode.app"

# Launch a job
procrastinate defer mycode.sum '{"a": 3, "b": 5}'

# Run a worker
procrastinate worker -q sums

Lastly, you can use Procrastinate asynchronously too (actually, it's the recommended way to use it):

import asyncio

import procrastinate

# Make an app in your code
app = procrastinate.App(connector=procrastinate.PsycopgConnector())

# Define tasks using coroutine functions
@app.task(queue="sums")
async def sum(a, b):
    await asyncio.sleep(a + b)

async with app.open_async():
    # Launch a job
    await sum.defer_async(a=3, b=5)

    # Somewhere in your program, run a worker (actually, it's often a
    # different program than the one deferring jobs for execution)
    await app.run_worker_async(queues=["sums"])

There are quite a few interesting features that Procrastinate adds to the mix. You can head to the Quickstart section for a general tour or to the How-To sections for specific features. The Discussion section should hopefully answer your questions. Otherwise, feel free to open an issue.

Note to my future self: add a quick note here on why this project is named "Procrastinate" ;) .

Where to go from here

The complete docs is probably the best place to learn about the project.

If you encounter a bug, or want to get in touch, you're always welcome to open a ticket.