🔮 Crono

Crono is a programmatic time-based job scheduler that gives your application a sense of timing.

import crono
crono.request('POST', 'https://your.app/').after(hours=42)

Install

Install package:

pip install crono

Run the servers:

redis-server &
celery worker --app=crono.queue:queue --hostname=worker1@%h
celery beat --app=crono.queue:queue

Usage

Triggers

A trigger defines when a job will be executed. There are 4 types of triggers: after, on, every, and cron.

after

after specifies a countdown until the execution of a task. It will only occur once. It takes at least 1 keyword argument: hours, minutes, and/or seconds, of type . Those keywords arguments are cumulative (same for the every trigger). For example, hours=1, minutes=30 equals minutes=90.

crono.after(minutes=30).…

on specifies the execution of a task at a specific date and time. It will only occur once. It takes 1 positional argument of type <datetime.datetime>.

import datetime
date = datetime.datetime(2019, 7, 4)
crono.on(date).…

every

every specifies a frequency at which to execute a task. It will occur multiple times. It takes at least 1 keyword argument: hours, minutes, and/or seconds, of type . Those keywords arguments are cumulative (similarly to the after trigger). For example, hours=1, minutes=30 equals minutes=90.

crono.every(hours=1, minutes=30).…

cron

cron uses an expression to specify the execution time. It will occur mutiple times. It takes exactly 1 positional argument of type <str>.

crono.cron('0 6 * * 2').…

Tasks

A task defines what a job will do. There are 4 types of tasks: log, request, message, and email.

log

log uses the standard logging Python library.

crono.log('DEBUG', '{text}', *args, **kwargs)

request

request sends an HTTP request. It is powered by the Requests library.

crono.request('POST', '{url}', **kwargs).…

message

message sends an SMS. It is powered by Twilio. To use it, you will have to specify twilio_account_sid and twilio_auth_id.

Not implemented, yet.

email

email sends an email. It is powered by Postmark. To use it, you will have to specify postmark_api_key and postmark_sender.

Not implemented, yet.

Examples

import crono

# Timer
crono.request('POST', '{url}').after(minutes=1)

# Datetime
crono.log('DEBUG', '{text}').on(<datetime>)

# Interval
crono.email(…).every(hours=1) # `email` task not implemented (yet)

# Cron
crono.message(…).cron('0 6 * * 2') # `message` task not implemented (yet)

Configuration

Crono comes with sensible default values that you can override:

# Required
CELERY_BROKER

# Optional
CELERY_RESULT_BACKEND
REDIS_MAX_CONNECTIONS (default: 20)	
CELERY_BROKER_POOL_LIMIT (default: 0)
CELERY_TASK_IGNORE_RESULT (default: True)
CELERY_BEAT_MAX_LOOP_INTERVAL (default: 300)
CELERY_WORKER_MAX_TASKS_PER_CHILD (default: 100)

Test

python -m pytest

Development

Packaging

# Generating distribution archives
$ python setup.py sdist bdist_wheel

# Uploading the distribution archives
$ twine upload --skip-existing dist/*

gduverger/crono