Why can't I connect to Cassandra on my MacOS?-CodePudding

I am using MAC OS (Monterey 12.2.1) Apple M1, Chip

PostgreSQL works fine for me but Cassandra doesn't. After installing and importing cassandra, I tried connecting to the local instance of Apache Cassandra as done below

import cassandra    
from cassandra.cluster import Cluster
try: 
   cluster = Cluster(['127.0.0.1']) 
   session = cluster.connect()
except Exception as e:
   print(e)

However I got the following error:

('Unable to connect to any servers', {'127.0.0.1:9042': ConnectionRefusedError(61, "Tried connecting to [('127.0.0.1', 9042)]. Last error: Connection refused")})

I have cassandra 4.0.3 installed and and I have tried many of the suggestions online but didn't work for me. I cannot even find files like cassandra-env.sh, cassandra.yaml

With the command java -version, I have:

java version "1.8.0_321"
Java(TM) SE Runtime Environment (build 1.8.0_321-b07)
Java HotSpot(TM) 64-Bit Server VM (build 25.321-b07, mixed mode)

CodePudding user response：

So it's not abundantly clear how Cassandra was installed on your Mac (homebrew, etc). But as another possible method of achieving this, I'll list out the steps about how I run Apache Cassandra on my Mac, and maybe that'll help you.

Download the tarball. For this example, I'll go with Apache Cassandra 4.0.3.

https://dlcdn.apache.org/cassandra/4.0.3/apache-cassandra-4.0.3-bin.tar.gz

Move the tarball to the desired location:

mv ~/Downloads/apache-cassandra-4.0.3-bin.tar.gz ~/local/

Untar:

cd ~/local
tar -zxvf apache-cassandra-4.0.3-bin.tar.gz
cd apache-cassandra-4.0.3

Configure (if you skip this step, it will) start:

atom conf/cassandra.yaml

Start:

bin/cassandra -p cassandra.pid

This ^ starts Cassandra with a PID file. That allows you to break-away from the output, and it will still keep running in the background (unlike bin/cassandra or bin/cassandra -f).

CodePudding user response：

This message indicates that there is no Cassandra instance running on localhost listening on port 9042:

('Unable to connect to any servers', {'127.0.0.1:9042': \
  ConnectionRefusedError(61, "Tried connecting to [('127.0.0.1', 9042)]. \
  Last error: Connection refused")})

You need to confirm that Cassandra is running on your Mac. The quickest way is to determine if there is a process listening on port 9042 with either of these commands:

$ netstat -tnlp

$ sudo lsof -nPi -sTCP:LISTEN

Cassandra by default listens for client connections on CQL port 9042 configured in cassandra.yaml with:

native_transport_port: 9042

Clients connect to Cassandra using the rpc_address in cassandra.yaml:

rpc_address: localhost

If you've set it to your Mac's IP address then you will need to use it as the contact point on this line of your app instead of localhost:

    cluster = Cluster(['127.0.0.1'])

If you're new to Cassandra, I recommend having a look at datastax.com/dev which has lots of free hands-on interactive learning resources. In particular, the Cassandra Fundamentals learning series lets you learn the basic concepts quickly. Cheers!