[英]Cannot query for particular UUID with Python cassandra-driver
[英]Python cassandra-driver OperationTimeOut on every query in Celery task
我在 celery 任务中异步执行的每个插入查询(小查询)都有问题。 在同步模式下,当我将所有内容插入都做得很好,但是当它在 apply_async() 中执行时,我得到了这个:
OperationTimedOut('errors=errors=errors={}, last_host=***.***.*.***, last_host=None, last_host=None',)
追溯:
Traceback (most recent call last):
File "/var/nfs_www/***/env_v0/local/lib/python2.7/site-packages/celery/app/trace.py", line 240, in trace_task
R = retval = fun(*args, **kwargs)
File "/var/nfs_www/***/env_v0/local/lib/python2.7/site-packages/celery/app/trace.py", line 437, in __protected_call__
return self.run(*args, **kwargs)
File "/var/nfs_www/***/www_v1/app/mods/news_feed/tasks.py", line 26, in send_new_comment_reply_notifications
send_new_comment_reply_notifications_method(comment_id)
File "/var/nfs_www/***www_v1/app/mods/news_feed/methods.py", line 83, in send_new_comment_reply_notifications
comment_type='comment_reply'
File "/var/nfs_www/***/www_v1/app/mods/news_feed/models/storage.py", line 129, in add
CommentsFeed(**kwargs).save()
File "/var/nfs_www/***/env_v0/local/lib/python2.7/site-packages/cqlengine/models.py", line 531, in save
consistency=self.__consistency__).save()
File "/var/nfs_www/***/env_v0/local/lib/python2.7/site-packages/cqlengine/query.py", line 907, in save
self._execute(insert)
File "/var/nfs_www/***/env_v0/local/lib/python2.7/site-packages/cqlengine/query.py", line 786, in _execute
tmp = execute(q, consistency_level=self._consistency)
File "/var/nfs_www/***/env_v0/local/lib/python2.7/site-packages/cqlengine/connection.py", line 95, in execute
result = session.execute(query, params)
File "/var/nfs_www/***/env_v0/local/lib/python2.7/site-packages/cassandra/cluster.py", line 1103, in execute
result = future.result(timeout)
File "/var/nfs_www/***/env_v0/local/lib/python2.7/site-packages/cassandra/cluster.py", line 2475, in result
raise OperationTimedOut(errors=self._errors, last_host=self._current_host)
OperationTimedOut: errors={}, last_host=***.***.*.***
有没有人对问题有想法?
我发现这个当 cassandra-driver 执行查询时,cassandra-driver 返回错误 OperationTimedOut ,但我的查询很少,并且仅在 celery 任务中出现问题。
更新:
我做了一个测试任务,它也引发了这个错误。
@celery.task()
def test_task_with_cassandra():
from app import cassandra_session
cassandra_session.execute('use news_feed')
return 'Done'
更新2:做了这个:
@celery.task()
def test_task_with_cassandra():
from cqlengine import connection
connection.setup(app.config['CASSANDRA_SERVERS'], port=app.config['CASSANDRA_PORT'],
default_keyspace='test_keyspace')
from .models import Feed
Feed.objects.count()
return 'Done'
明白啦:
NoHostAvailable('Unable to connect to any servers', {'***.***.*.***': OperationTimedOut('errors=errors=Timed out creating connection, last_host=None, last_host=None',)})
从外壳我可以连接到它
更新 3 :从 github 问题上的已删除线程(在我的电子邮件中找到):(这对我也有用)实际上,我将 CQLengine 插入 Celery 的方法如下:
from celery import Celery
from celery.signals import worker_process_init, beat_init
from cqlengine import connection
from cqlengine.connection import (
cluster as cql_cluster, session as cql_session)
def cassandra_init():
""" Initialize a clean Cassandra connection. """
if cql_cluster is not None:
cql_cluster.shutdown()
if cql_session is not None:
cql_session.shutdown()
connection.setup()
# Initialize worker context for both standard and periodic tasks.
worker_process_init.connect(cassandra_init)
beat_init.connect(cassandra_init)
app = Celery()
这很粗糙,但有效。 我们应该在 FAQ 中添加这个片段吗?
我有一个类似的问题。 这似乎与在任务之间共享 Cassandra 会话有关。 我通过为每个线程创建一个会话来解决它。 确保从任务中调用get_session()
,然后执行以下操作:
thread_local = threading.local()
def get_session():
if hasattr(thread_local, "cassandra_session"):
return thread_local.cassandra_session
cluster = Cluster(settings.CASSANDRA_HOSTS)
session = cluster.connect(settings.CASSANDRA_KEYSPACE)
thread_local.cassandra_session = session
return session
受罗恩回答的启发,我想出了以下代码放入tasks.py:
import threading
from django.conf import settings
from cassandra.cluster import Cluster
from celery.signals import worker_process_init,worker_process_shutdown
thread_local = threading.local()
@worker_process_init.connect
def open_cassandra_session(*args, **kwargs):
cluster = Cluster([settings.DATABASES["cassandra"]["HOST"],], protocol_version=3)
session = cluster.connect(settings.DATABASES["cassandra"]["NAME"])
thread_local.cassandra_session = session
@worker_process_shutdown.connect
def close_cassandra_session(*args,**kwargs):
session = thread_local.cassandra_session
session.shutdown()
thread_local.cassandra_session = None
这个简洁的解决方案将在 celery 工作进程启动和停止时自动打开/关闭 cassandra 会话。
旁注:protocol_version=3,因为 Cassandra 2.1 仅支持协议版本 3 及更低版本。
其他答案对我不起作用,但问题的“更新 3”起作用了。 这是我的最终结果(对问题中的建议进行了小幅更新):
from celery.signals import worker_process_init
from cassandra.cqlengine import connection
from cassandra.cqlengine.connection import (
cluster as cql_cluster, session as cql_session)
def cassandra_init(*args, **kwargs):
""" Initialize a clean Cassandra connection. """
if cql_cluster is not None:
cql_cluster.shutdown()
if cql_session is not None:
cql_session.shutdown()
connection.setup(settings.DATABASES["cassandra"]["HOST"].split(','), settings.DATABASES["cassandra"]["NAME"])
# Initialize worker context (only standard tasks)
worker_process_init.connect(cassandra_init)
使用 django-cassandra-engine 以下为我解决了这个问题:
db_connection = connections['cassandra']
@worker_process_init.connect
def connect_db(**_):
db_connection.reconnect()
@worker_shutdown.connect
def disconnect(**_):
db_connection.connection.close_all()
看这里
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