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Question

我正在尝试编写一个类，ChangeBackStatusOnErrorTask，它完全符合其名称的含义。

class ChangeBackStatusOnErrorTask(Task):
abstract = True
def on_failure(self, exc, task_id, args, kwargs, einfo):
server = Server.query.get(server_id)
server.status = RemoteStatus.ERROR
db.session.commit()

@celery.task(bind=True, base=ChangeBackStatusOnErrorTask)
def deploy_server(self, server_id):
try:
server.status = RemoteStatus.LAUNCHING
db.session.commit()
host = server.ssh_user + '@' + server.ip
execute(fabric_deploy_server, self, server, hosts=host)
server.status = RemoteStatus.LAUNCHED
db.session.commit()
except Exception as e:
server.status = RemoteStatus.ERROR
db.session.commit()
traceback.print_exc()
raise e

但是，由于ChangeBackStatusOnErrorTask未绑定到我的Flask上下文，因此此代码不起作用：

File "/Users/vng/.virtualenvs/AutomataHeroku/lib/python2.7/site-packages/celery/app/trace.py", line 367, in trace_task
R = retval = fun(*args, **kwargs)
File "/Users/vng/.virtualenvs/AutomataHeroku/lib/python2.7/site-packages/celery/app/trace.py", line 622, in __protected_call__
return self.run(*args, **kwargs)
File "/Users/vng/Dropbox/Code/Affiliate/AutomataHeroku/automata/server/tasks.py", line 59, in deploy_server
server = Server.query.get(server_id)
File "/Users/vng/.virtualenvs/AutomataHeroku/lib/python2.7/site-packages/flask_sqlalchemy/__init__.py", line 498, in __get__
return type.query_class(mapper, session=self.sa.session())
File "/Users/vng/.virtualenvs/AutomataHeroku/lib/python2.7/site-packages/sqlalchemy/orm/scoping.py", line 78, in __call__
return self.registry()
File "/Users/vng/.virtualenvs/AutomataHeroku/lib/python2.7/site-packages/sqlalchemy/util/_collections.py", line 990, in __call__
return self.registry.setdefault(key, self.createfunc())
File "/Users/vng/.virtualenvs/AutomataHeroku/lib/python2.7/site-packages/sqlalchemy/orm/session.py", line 2861, in __call__
return self.class_(**local_kw)
File "/Users/vng/.virtualenvs/AutomataHeroku/lib/python2.7/site-packages/flask_sqlalchemy/__init__.py", line 143, in __init__
self.app = app = db.get_app()
File "/Users/vng/.virtualenvs/AutomataHeroku/lib/python2.7/site-packages/flask_sqlalchemy/__init__.py", line 957, in get_app
'application not registered on db instance and no application'
RuntimeError: application not registered on db instance and no application bound to current context

我该如何解决这个问题？

Answer 1

我假设您使用sqlachemy和flask-sqlalchemy扩展。并且您从某个专用模块获取db对象，并且该对象也绑定到烧瓶实例(请编辑您的问题以澄清这一点(。

在app模块中声明您的芹菜配置：

app = Flask(__name__)
app.config[CELERY_BROKER_URL] = 'redis://localhost:6379'
app.config[CELERY_RESULT_BACKEND] = 'redis://localhost:6379'

然后在您的芹菜模块中，您需要将其绑定到烧瓶中：

from celery import Celery
from app import current_app as app
def bound_celery(app): 
celery = Celery(
app.import_name,
backend=app.config['CELERY_RESULT_BACKEND'],      
broker=app.config['CELERY_BROKER_URL']
)
celery.conf.update(app.config)    
TaskBase = celery.Task 
class ContextTask(TaskBase): 
abstract = True 
def __call__(self, *args, **kwargs): 
with app.app_context(): 
return TaskBase.__call__(self, *args, **kwargs)
celery.Task = ContextTask
return celery
celery = bound_celery(app)

最后使用celery创建的对象来装饰您的任务：

@celery.task(bind=True, base=ChangeBackStatusOnErrorTask) 
def deploy_server(self, server_id):
...

来源：烧瓶文档