python - 我是一个 celery 初学者，只限于基本用法……甚至无法进入task.delay()

Question

我试图以 flask 初学者的身份将Celery异步功能添加到我的简单 flask Web项目中。在设法安装并启动了celery，redis和相关的python pip东西之后，我从一开始就为delay()苦苦挣扎。看来我什至无法进入delay()。我很沮丧，你能帮我吗？

我的flask项目下有app.py和tasks.py。 (起初，我将所有内容都写在app.py中，然后将 celery 对象分割开了，这没有帮助)

task.py:

from celery import Celery

celery = Celery('app', broker='redis://localhost:6379/0', backend='redis://localhost:6379/1')


@celery.task
def modeling_task():
    print('yes')

app.py:

@app.route('/train', methods=['GET', 'POST'])
def train():
    if request.method == "GET":
        return render_template('train.html')
    else:  # when request POST
        # check if the post request has the file part
        if 'file' not in request.files:
            return jsonify({"code": 500, "status": 'No file is uploaded!'})

        if file and allowed_file(file.filename):
            print(request.files['file'].filename)
            print('before task')
            task = modeling_task.delay()
            print('after task')

            return jsonify({"code": 200, "status": 'model training', "task_id": task.id})

        return 'Uploading file is wrong'

如果一切正常，则服务器收到上传文件后，控制台上的打印结果应为

Car_TEST.csv
before task
yes
after task

但是，控制台结果就是这样

 * Detected change in 'C:\\Users\\headmaster\\Desktop\\WEB\\tasks.py', reloading
 * Restarting with stat
 * Debugger is active!
 * Debugger PIN: 308-608-393
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
127.0.0.1 - - [22/Apr/2020 11:39:22] "GET /train HTTP/1.1" 200 -
Car_TEST.csv
before task

并且服务器卡在这里，不断地运行。

因此，似乎服务器甚至没有运行“task = modeling_task.delay()”，否则它应该在控制台上打印“yes”，对吗？

它会在另一个地方打印"is"吗？为什么卡住了？
celery report输出:

(base) C:\Users\headmaster\Desktop\WEB>celery -A tasks report

software -> celery:4.4.2 (cliffs) kombu:4.6.8 py:3.7.4
            billiard:3.6.3.0 redis:3.4.1
platform -> system:Windows arch:64bit, WindowsPE
            kernel version:10 imp:CPython
loader   -> celery.loaders.app.AppLoader
settings -> transport:redis results:redis://localhost:6379/1

broker_url: 'redis://localhost:6379/0'
result_backend: 'redis://localhost:6379/1'

下面是 celery 信息:

(base) C:\Users\headmaster\Desktop\WEB>celery worker -A tasks.celery --loglevel=info

 -------------- celery@LAPTOP-KLKJCK2F v4.4.2 (cliffs)
--- ***** -----
-- ******* ---- Windows-10-10.0.18362-SP0 2020-04-22 10:55:13
- *** --- * ---
- ** ---------- [config]
- ** ---------- .> app:         app:0x2526977ac08
- ** ---------- .> transport:   redis://localhost:6379/0
- ** ---------- .> results:     redis://localhost:6379/1
- *** --- * --- .> concurrency: 4 (prefork)
-- ******* ---- .> task events: OFF (enable -E to monitor tasks in this worker)
--- ***** -----
 -------------- [queues]
                .> celery           exchange=celery(direct) key=celery


[tasks]
  . tasks.modeling_task

[2020-04-22 10:55:15,501: INFO/SpawnPoolWorker-1] child process 6692 calling self.run()
[2020-04-22 10:55:15,511: INFO/SpawnPoolWorker-2] child process 17736 calling self.run()
[2020-04-22 10:55:15,518: INFO/SpawnPoolWorker-3] child process 16320 calling self.run()
[2020-04-22 10:55:15,571: INFO/SpawnPoolWorker-4] child process 5608 calling self.run()
[2020-04-22 10:55:15,972: INFO/MainProcess] Connected to redis://localhost:6379/0
[2020-04-22 10:55:20,332: INFO/MainProcess] mingle: searching for neighbors
[2020-04-22 10:55:27,369: INFO/MainProcess] mingle: all alone
[2020-04-22 10:55:35,402: INFO/MainProcess] celery@LAPTOP-KLKJCK2F ready.

Redis信息:

PS D:\Applications\Redis> redis-server redis.conf
                _._
           _.-``__ ''-._
      _.-``    `.  `_.  ''-._           Redis 3.2.100 (00000000/0) 64 bit
  .-`` .-```.  ```\/    _.,_ ''-._
 (    '      ,       .-`  | `,    )     Running in standalone mode
 |`-._`-...-` __...-.``-._|'` _.-'|     Port: 6379
 |    `-._   `._    /     _.-'    |     PID: 21420
  `-._    `-._  `-./  _.-'    _.-'
 |`-._`-._    `-.__.-'    _.-'_.-'|
 |    `-._`-._        _.-'_.-'    |           http://redis.io
  `-._    `-._`-.__.-'_.-'    _.-'
 |`-._`-._    `-.__.-'    _.-'_.-'|
 |    `-._`-._        _.-'_.-'    |
  `-._    `-._`-.__.-'_.-'    _.-'
      `-._    `-.__.-'    _.-'
          `-._        _.-'
              `-.__.-'

[21420] 22 Apr 10:38:22.506 # Server started, Redis version 3.2.100
[21420] 22 Apr 10:38:22.508 * DB loaded from disk: 0.000 seconds
[21420] 22 Apr 10:38:22.508 * The server is now ready to accept connections on port 6379
[21420] 22 Apr 10:43:23.025 * 10 changes in 300 seconds. Saving...
[21420] 22 Apr 10:43:23.030 * Background saving started by pid 6204
[21420] 22 Apr 10:43:23.231 # fork operation complete
[21420] 22 Apr 10:43:23.232 * Background saving terminated with success
[21420] 22 Apr 10:51:18.099 * 10 changes in 300 seconds. Saving...
[21420] 22 Apr 10:51:18.103 * Background saving started by pid 10116
[21420] 22 Apr 10:51:18.305 # fork operation complete
[21420] 22 Apr 10:51:18.306 * Background saving terminated with success
[21420] 22 Apr 10:56:19.022 * 10 changes in 300 seconds. Saving...
[21420] 22 Apr 10:56:19.026 * Background saving started by pid 11748
[21420] 22 Apr 10:56:19.227 # fork operation complete
[21420] 22 Apr 10:56:19.227 * Background saving terminated with success

Answer 1

因此，这有点陈旧，但希望能对您有所帮助。
基本上，flask可能会阻止该过程，并且甚至在利用此处的信息https://www.distributedpython.com/2018/08/21/celery-4-windows/时，即使在设置了fork过程的情况下，也不允许在开发环境中的Windows上执行celery函数调用/任务。
如果您有生产设置，则要移植到Windows，则可能看不到该问题。我建议在Windows的开发环境中为flask应用程序安装wsgi包装器。
创建一个名为wsgi.py的文件

from gevent.pywsgi import WSGIServer # <--- install gevent if you dont have it
from app import app # <--- flask app

http_server = WSGIServer(('', <port>), app)
http_server.serve_forever()

在Windows上使用 celery 4.4.6和Windows的 redis端口进行了测试