Celery Beat无法正常调度任务并冻结问题求助

我最近碰到了Celery Beat的棘手问题——它没法正常调度任务，直接冻住了！用的是Celery 4.1.0版本，以下是我的相关配置、任务代码和运行日志，麻烦各位大佬帮忙看看怎么解决，万分感谢！

环境与配置 #

我的Celery配置如下：

CELERY_BROKER_URL = 'redis://127.0.0.1:6379'
CELERY_ACCEPT_CONTENT = ['application/json']
CELERY_RESULT_SERIALIZER = 'json'
CELERY_TASK_SERIALIZER = 'json'
CELERY_TIMEZONE = 'Asia/Kolkata'
CELERY_ACCEPT_CONTENT += ['pickle']
CELERYBEAT_SCHEDULE = {
    'testing_msg': {
        'task': 'modules.sms.tasks.testing_message',
        'schedule': crontab(minute=1),
    },
}

任务代码（tasks.py） #

对应的任务实现：

@task()
def testing_message(*args, **kwargs):
    SmsAPI().send_sms("Hello Shubham Message Time is {}".format(datetime.now().time()), "958xxxxxx")
    SmsAPI().send_sms("Hello Nishant Message Time is {}".format(datetime.now().time()), "971xxxxxx")

Celery Beat运行日志 #

启动Beat时的命令是celery -A config beat -l debug raven settings，日志输出如下：

shubham@shuboy2014:/media/shubham/BC161A021619BDF8/Nishant Project/Project1$ celery -A config beat -l debug raven settings
celery beat v4.1.0 (latentcall) is starting.
__ - ... __ - _
LocalTime -> 2018-01-04 14:57:53
Configuration ->
    . broker -> redis://127.0.0.1:6379//
    . loader -> celery.loaders.app.AppLoader
    . scheduler -> celery.beat.PersistentScheduler
    . db -> celerybeat-schedule
    . logfile -> [stderr]@%DEBUG
    . maxinterval -> 5.00 minutes (300s)
[2018-01-04 14:57:53,139: DEBUG/MainProcess] Setting default socket timeout to 30
[2018-01-04 14:57:53,139: INFO/MainProcess] beat: Starting...
[2018-01-04 14:57:53,334: DEBUG/MainProcess] Current schedule: <ScheduleEntry: celery.backend_cleanup celery.backend_cleanup() <crontab: 0 4 * * * (m/h/d/dM/MY)>
[2018-01-04 14:57:53,334: DEBUG/MainProcess] beat: Ticking with max interval->5.00 minutes
[2018-01-04 14:57:53,336: DEBUG/MainProcess] beat: Waking up in 5.00 minutes.

目前日志显示Beat启动后就一直处于"唤醒等待5分钟"的状态，到了我设定的调度时间（每分钟的第1分钟）也完全没触发testing_msg任务，完全没动静。有没有大佬遇到过类似问题？求指点可行的解决方案！

内容的提问来源于stack exchange，提问作者shuboy2014