Example using the Eventlet Pool

Introduction

This is a Celery application containing two example tasks.

First you need to install Eventlet, and also recommended is the dnspython module (when this is installed all name lookups will be asynchronous):

$ pip install eventlet
$ pip install dnspython
$ pip install requests

Before you run any of the example tasks you need to start the worker:

$ cd examples/eventlet
$ celery worker -l info --concurrency=500 --pool=eventlet

As usual you need to have RabbitMQ running, see the Celery getting started guide if you haven't installed it yet.

Tasks

• tasks.urlopen

This task simply makes a request opening the URL and returns the size of the response body:

$ cd examples/eventlet
$ python
>>> from tasks import urlopen
>>> urlopen.delay('http://www.google.com/').get()
9980

To open several URLs at once you can do:

$ cd examples/eventlet
$ python
>>> from tasks import urlopen
>>> from celery import group
>>> result = group(urlopen.s(url)
...                     for url in LIST_OF_URLS).apply_async()
>>> for incoming_result in result.iter_native():
...     print(incoming_result)

• webcrawler.crawl

This is a simple recursive web crawler. It will only crawl URLs for the current host name. Please see comments in the webcrawler.py file.