Distributed Python job queue with asyncio and redis
Project description
SAQ
SAQ (Simple Async Queue) is a simple and performant job queueing framework built on top of asyncio and redis. It can be used for processing background jobs with workers. For example, you could use SAQ to schedule emails, execute long queries, or do expensive data analysis.
It uses redis-py >= 4.2.
It is similar to RQ and heavily inspired by ARQ. Unlike RQ, it is async and thus significantly faster if your jobs are async. Even if they are not, SAQ is still considerably faster due to lower overhead.
SAQ optionally comes with a simple UI for monitor workers and jobs.
Install
# minimal install
pip install saq
# web + hiredis
pip install saq[web,hiredis]
Usage
usage: saq [-h] [--workers WORKERS] [--verbose] [--web]
[--extra-web-settings EXTRA_WEB_SETTINGS]
[--port PORT] [--check]
settings
Start Simple Async Queue Worker
positional arguments:
settings Namespaced variable containing
worker settings eg: eg
module_a.settings
options:
-h, --help show this help message and exit
--workers WORKERS Number of worker processes
--verbose, -v Logging level: 0: ERROR, 1: INFO,
2: DEBUG
--web Start web app. By default, this
only monitors the current
worker's queue. To monitor
multiple queues, see '--extra-
web-settings'
--extra-web-settings EXTRA_WEB_SETTINGS, -e EXTRA_WEB_SETTINGS
Additional worker settings to
monitor in the web app
--port PORT Web app port, defaults to 8080
--check Perform a health check
environment variables:
AUTH_USER basic auth user, defaults to admin
AUTH_PASSWORD basic auth password, if not specified, no auth will be used
Example
import asyncio
from saq import CronJob, Queue
# all functions take in context dict and kwargs
async def test(ctx, *, a):
await asyncio.sleep(0.5)
# result should be json serializable
# custom serializers and deserializers can be used through Queue(dump=,load=)
return {"x": a}
async def cron(ctx):
print("i am a cron job")
async def startup(ctx):
ctx["db"] = await create_db()
async def shutdown(ctx):
await ctx["db"].disconnect()
async def before_process(ctx):
print(ctx["job"], ctx["db"])
async def after_process(ctx):
pass
queue = Queue.from_url("redis://localhost")
settings = {
"queue": queue,
"functions": [test],
"concurrency": 10,
"cron_jobs": [CronJob(cron, cron="* * * * * */5")], # run every 5 seconds
"startup": startup,
"shutdown": shutdown,
"before_process": before_process,
"after_process": after_process,
}
To start the worker, assuming the previous is available in the python path
saq module.file.settings
Note:
module.file.settingscan also be a callable returning the settings dictionary.
To enqueue jobs
# schedule a job normally
job = await queue.enqueue("test", a=1)
# wait 1 second for the job to complete
await job.refresh(1)
print(job.results)
# run a job and return the result
print(await queue.apply("test", a=2))
# Run multiple jobs concurrently and collect the results into a list
print(await queue.map("test", [{"a": 3}, {"a": 4}]))
# schedule a job in 10 seconds
await queue.enqueue("test", a=1, scheduled=time.time() + 10)
Demo
Start the worker
python -m saq examples.simple.settings --web
Navigate to the web ui
Enqueue jobs
python examples/simple.py
Comparison to ARQ
SAQ is heavily inspired by ARQ but has several enhancements.
- Avoids polling by leveraging BLMOVE or RPOPLPUSH and NOTIFY
- SAQ has much lower latency than ARQ, with delays of < 5ms. ARQ's default polling frequency is 0.5 seconds
- SAQ is up to 8x faster than ARQ
- Web interface for monitoring queues and workers
- Heartbeat monitor for abandoned jobs
- More robust failure handling
- Storage of stack traces
- Sweeping stuck jobs
- Handling of cancelled jobs different from failed jobs (machine redeployments)
- Before and after job hooks
- Easily run multiple workers to leverage more cores
Development
python -m venv env
source env/bin/activate
pip install -e ".[dev,web]"
docker run -d -p 6379:6379 redis
docker run -d -p 5432:5432 -e POSTGRES_HOST_AUTH_METHOD=trust postgres
make lint test
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