Install redis in your dev environment:
apt-get install redis-server pip install redis
Then install ‘pymacaron-async’:
pip install pymacaron-async
And add it to your microservice dependencies:
echo 'pymacaron-async' >> requirements.txt
Instruct the pymacaron server to start celery workers by adding the following line in ‘pym-config.yaml’:
And make python methods asynchronous by decorating them as follows:
from pymacaron_async import asynctask from pymacaron_core.swagger.apipool import ApiPool # Make send_email_async() into an asynchronously # executable celery task, executed separately # a celery worker spawned by the PyMacaron framework @asynctask() def send_email_async(title): # Call 3-rd party emailing API pass pass # API endpoint, defined in your swagger API spec def do_signup_user(): do_stuff() # Schedule a task sending this email # and go on, not waiting for the result send_email_async('Welcome !') return ApiPool.myapi.model.Ok()
NOTE: it is a good idea to have a naming convention for methods decorated with @asynctask, such as appending ‘_async’ to their names. This will make your code easier to understand.
If you want to delay execution of the asynchronous task:
# Delay 1min (60secs) @asyntask(delay=60)
Arguments to the asynchronous methods should not be classes instances, since celery won’t serialize them correctly when passing them to the asynchronous task. Dicts, arrays and native python types work fine.
It is considered good behavior for a REST api endpoint to return as quickly as possible. Any long running task it needs to perform, such as image manipulation, 3rd party calls whose replies are not immediately needed, logging or analytics, should be executed asynchronously so as to not delay the HTTP response to the api caller.
Unfortunately, this is not trivially done. Except with pymacaron-async :-)
pymacaron-async adds asynchronous execution capability to pymacaron servers, by spawning in the background a celery worker in which all your api modules are loaded. The celery worker loads your swagger api files in just the same way as the pymacaron server, imports all the modules containing your endpoint implementations and emulates a Flask context including the current user’s authentication token. That way, code executed asynchronously in a celery task sees exactly the same context as code executing synchronously in the endpoint method.