Using Flask with Celery on Ubuntu

Celery Environment

  • backend: redis
  • broker: redis

Installation

  • redis server 
    $ apt-get install redis-server
  • python library
    $ pip install redis
$ pip install celery

Project Structure

project
  ├── __init__.py
  ├── web.py
  ├── work
    ├── __init__.py
    ├── worker.py
  ├── templates
    ├── index.html
  • worker.py
from celery import Celery

cel = Celery('work',
             backend='redis://127.0.0.1:6379/',
             broker='redis://127.0.0.1:6379/')

@cel.task
def expensive_function(x, y):
    return x + y
  • web.py
from flask import Flask, render_template
from work.worker import expensive_function

app = Flask(__name__)

@app.route('/', methods=['GET'])
def index():
    result = expensive_function.delay(3, 3)
    return render_template("index.html",
                           val=result.wait())

if __name__ == '__main__':
    app.run()
  • index.html
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Index</title>
</head>
<body>
<h1>The value from celery's expensive function is {{ val }}</h1>
</body>
</html>

Execution

  • If redis is not working, running redis.

    $ redis-server

  • Check redis is working.

    $ redis-cli ping
PONG

  • Start redis in interactive mode, you can know which ip and port is redis running.

    $ redis-cli                                                                
redis 127.0.0.1:6379>

  • Go to project directory

    $ cd /your_project_path/project

  • Run celery worker

    $ celery -A work.worker worker --loglevel=info --concurrency=2
    • --loglevel=info: print log on terminal
    • --concurrency=2: specify the number of threads

  • Run flask web app

    $ python web.py

  • Now, you can visit your web site, the web index will print The value from celery's expensive function is 6.

  • And, the celery log will print Received task successfully and return the 6 of computing result at same time.

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