Python Cassandra无法对任何主机完成该操作

我正在尝试使用Python在ApacheCassandra上运行一些插入查询。我想插入json文件中的数据，下面是我的代码：

import logging
from cassandra.cluster import Cluster

import json

logging.basicConfig(level=logging.INFO)


def connect_db():
    """Func to connect to cassandra db"""

    cluster = Cluster(['127.0.0.1'], port=9042)
    session = cluster.connect()

    # session.execute("DROP TABLE player_session.events")
    # session.execute("DROP TABLE player_session.startevents ")
    # session.execute("DROP TABLE player_session.endevents ")

    return session


def execute_query():
    """Func to execute query in cassandra """
    session = connect_db()

    print("Creating KEYSPACE")
    session.execute("""
        CREATE KEYSPACE IF NOT EXISTS player_session 
        WITH REPLICATION = 
        { 'class' : 'NetworkTopologyStrategy', 'data_center' : 1 }
    """)

    print("Creating player_session table")
    session.execute("""
    CREATE TABLE IF NOT EXISTS 
    player_session.events(player_id text, country text, event text, session_id text,ts timestamp, 
    PRIMARY KEY(player_id, ts)) WITH CLUSTERING ORDER BY ("ts" DESC)
    """)

    print("Creating start session table")
    session.execute("""
    CREATE TABLE IF NOT EXISTS 
    player_session.startevents(player_id text, country text, event text, session_id text,ts timestamp, 
    PRIMARY KEY(player_id, ts)) WITH CLUSTERING ORDER BY ("ts" DESC)
    """)

    print("Creating end session table")
    session.execute("""
    CREATE TABLE IF NOT EXISTS 
    player_session.endevents(player_id text, country text, event text, session_id text,ts timestamp, 
    PRIMARY KEY(player_id, ts)) WITH CLUSTERING ORDER BY ("ts" DESC)
    """)

    return session


def insert_data(session):
    """Func to insert json data """
    with open('my_json.jsonl') as f:
        data = f.readlines()

    for row in data:
        row = json.loads(row)
        if row['event'] == "start":
            session.execute(
                "INSERT INTO  player_session.startevents  (player_id,  event, country, session_id, ts) VALUES (%s,%s,%s,%s,%s) ",
                [row['player_id'], row['event'], row['country'], row['session_id'], row['ts']]
            )
        if row['event'] == "end":
            session.execute(
                "INSERT INTO  player_session.endevents  (player_id,  event, session_id, ts) VALUES (%s,%s,%s,%s) ",
                [row['player_id'], row['event'], row['session_id'], row['ts']]
            )
    f.close()
    print("data import complete")


if __name__ == "__main__":
    session = connect_db()
    insert_data(session)

我的表是用Cassandra创建的，但我总是会遇到以下错误：

Traceback (most recent call last):
 line 64, in insert_data
    session.execute(
  File "cassandra/cluster.py", line 2618, in cassandra.cluster.Session.execute
  File "cassandra/cluster.py", line 4894, in cassandra.cluster.ResponseFuture.result
cassandra.cluster.NoHostAvailable: ('Unable to complete the operation against any hosts', {<Host: 127.0.0.1:9042 datacenter1>: Unavailable('Error from server: code=1000 [Unavailable exception] message="Cannot achieve consistency level LOCAL_ONE" info={\'consistency\': \'LOCAL_ONE\', \'required_replicas\': 1, \'alive_replicas\': 0}')})

回溯（最近一次呼叫最后一次）：
第64行，插入_数据
session.execute(
文件“cassandra/cluster.py”，第2618行，位于cassandra.cluster.Session.execute中
文件“cassandra/cluster.py”，第4894行，位于cassandra.cluster.ResponseFuture.result中
cassandra.cluster.NoHostAvailable:（“无法完成对任何主机的操作”，{：不可用（'Error from server:code=1000[Unavailable exception]message=“无法实现本地\u ONE”一致性级别信息={“一致性\'：\'LOCAL\u ONE\”，\'required\u replications\'：1，\'alive\u replications\'：0}）

错误消息提示了两种可能性：

Cassandra未运行。您可以使用

nodetool status

验证这一点

您用于连接的数据中心名称在键空间定义或群集配置中不正确。数据中心的默认名称为

dc1

。无论设置为什么，它都必须与数据中心名称相匹配，如

nodetool status

、

descripe keyspace player_session

和连接属性中指定的中心名称（可选）

---

我知道很多流行的Cassandra教程都演示了如何从应用程序代码内部构建架构。我建议不要使用这种做法，因为这可能会导致问题。只是把它放在那里。非常感谢您，它非常有效！我花了这么长时间才发现问题！@AlexBrunet非常好！很高兴您能使用它！