Cassandra Practices

Apache Cassandra is a free open-source database system that is NoSQL based. Meaning Cassandra does not use the table model seen in MySQL, MSSQL or PostgreSQL, but instead uses a cluster model. It’s designed to handle large amounts of data and is highly scalable.

Install Cassandra on Ubuntu

Install Java(JRE) 8+

sudo add-apt-repository ppa:webupd8team/java
sudo apt update
sudo apt-get install oracle-java8-set-default
java -version

Install Python 2.7+

sudo apt install python
python --version

Install Cassandra

  • First, we have to add Cassandra repository to source list by running following command. The 39x is the version. Use 40x if Cassandra 4.0 is the newest version:
echo "deb http://www.apache.org/dist/cassandra/debian 39x main" | \
sudo tee -a /etc/apt/sources.list.d/cassandra.sources.list
  • Next, run the cURL command to add the repository keys :
curl https://www.apache.org/dist/cassandra/KEYS | \
sudo apt-key add -
  • We can now update the repositories and install Cassandra:
sudo apt-get update
sudo apt install cassandra
# optional - It works on MacBook
sudo reboot
  • Check Cassandra status
nodetool status

Install Cassandra with Docker

Create node n1

docker run --name n1 -d tobert/cassandra -dc DC1 -rack RAC1
docker ps

Get IP of node n1

IP=`docker inspect -f '{{ .NetworkSettings.IPAddress }}' n1`
echo $IP

Check status of n1

docker exec -it n1  nodetool status

# You will see status of Datacenter D1 below

# Datacenter: DC1
# ===============
# Status=Up/Down
# |/ State=Normal/Leaving/Joining/Moving
# --  Address     Load       Tokens  Owns (effective)  Host ID   Rack
UN  172.17.0.2  51.53 KB   256     100.0%    8965869d-cae8-41a6-bf19-ff69c2605c6c  RAC1

Create node n2 on rack RAC2

docker run --name=n2 -d tobert/cassandra -dc DC1 -rack RAC2 --seeds $IP

docker exec -it n1  nodetool status

# You will see status of Datacenter D1 below

# Datacenter: DC1
# ===============
# Status=Up/Down
# |/ State=Normal/Leaving/Joining/Moving
# --  Address     Load       Tokens  Owns (effective)  Host ID   Rack
# UN  172.17.0.3  72.01 KB   256     100.0%  cfa002b0-350c-41b8-9f86-eb8978a43b26  RAC2
# UN  172.17.0.2  51.53 KB   256     100.0%  8965869d-cae8-41a6-bf19-ff69c2605c6c  RAC1

Check node n2 configuration

docker exec -it n2  cat /data/conf/cassandra.yaml | grep endpoint
docker exec -it n2  cat /data/conf/cassandra-rackdc.properties | grep  -e "dc"  -e "rack"

Create node n3 on Datacenter D2 and rack RAC1

docker run --name=n3 -d tobert/cassandra -dc DC2 -rack RAC1 --seeds $IP
docker exec -it n1  nodetool status

# You will see status below. It may take a few seconds to get everything up and run.

# Datacenter: DC1
# ===============
# Status=Up/Down
# |/ State=Normal/Leaving/Joining/Moving
# --  Address     Load    Tokens  Owns (effective)  Host ID  Rack
# UN  172.17.0.3  134.03 KB  256     66.1%             cfa002b0-350c-41b8-9f86-eb8978a43b26  RAC2
# UN  172.17.0.2  102.84 KB  256     64.5%             8965869d-cae8-41a6-bf19-ff69c2605c6c  RAC1

# Datacenter: DC2
# ===============
# Status=Up/Down
# |/ State=Normal/Leaving/Joining/Moving
# --  Address   Load   Tokens  Owns (effective)  Host ID   Rack
UN  172.17.0.4  14.38 KB   256     69.4%             0fad8335-763d-42fa-9934-3ed10c44eaa8  RAC1

Setup replication strategy

docker 
create keyspace csdb with replication = {'class':'NetworkTopologyStrategy','DC1':2,'DC2':1}

Check csdb status

docker exec -it n1 nodetool describering csdb

# Run nodetool status and note that the one node in DC2 owns all the data
docker exec -it n1 nodetool status csdb  

# Stop and remove all four docker containers:
docker stop n1 n2 n3 n4; docker rm n1 n2 n3 n4

Create single Datacenter with 3 nodes

Create 3 nodes with local mounted directory

docker run --name=n1 -v $PWD/ws/ps/cassdev/scripts:/scripts -d tobert/cassandra
docker exec -it n1  nodetool status

IP=`docker inspect -f '{{ .NetworkSettings.IPAddress }}' n1`
echo $IP

docker run --name=n2 -d tobert/cassandra --seeds $IP
docker run --name=n3 -d tobert/cassandra --seeds $IP

docker exec -it n1 /bin/bash
cd scripts

List scripts

docker exec -it n1 /bin/bash
cd /scrpts && ls

Create keyspace with simple replication

docker exec -it n1 cqlsh
create keyspace csdb with replication = 
{'class':'SimpleStrategy', 'replication_factor':1};

Create table and insert data with script

docker exec -it n1 cqlsh

> desc keyspaces;
> desc tables;
> use ussdb;
> source '/scripts/courses.cql'
> source '/scripts/users.cql'

CQL

docker exec -it n1 cqlsh

> use ussdb;
> desc tables;
> select * from users;
> select * from courses;

Troubleshoot

  • Connection error

    Connection error: Could not connect to localhost:9160
    • Update the configuration - cassandra.yaml

    • Change the following IP address

          - seeds: "xxx.xxx.xxx.xxx"
  listen_address: xxx.xxx.xxx.xxx
  broadcast_rpc_address: xxx.xxx.xxx.xxx

    • Restart the cassandra

      sudo systemctl restart cassandra