CODEWITHSUNDEEP
pythoncassandrarest
AlexBrunet
AlexBrunet

Reputation: 87

Python Cassandra Unable to complet the operation agains any host

I'm try to run some insert queries on Apache Cassandra using Python. I want to insert the data from a json file, here's my code:

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)

My tables are created in Cassandra but I will always get this error:

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}')})

Upvotes: 1

Views: 509

Answers (1)

Aaron
Aaron

Reputation: 57748

The error message suggests two possibilities:

  1. Cassandra is not running. You can verify this with nodetool status.

  2. The data center name you are using to connect is incorrect, either in the keyspace definition or in the cluster config. The default name for the data center is dc1. Whatever this is set to, it must match the data center name as shown in nodetool status, describe keyspace player_session, and the data center name specified in your connection properties (optional).

Upvotes: 1

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