The Cassandra NoSQL database is ideal for situations requiring maximum data redundancy and uptime, ease of horizontal scaling across multiple unique servers, and rapidly evolving project demands during the development life cycle which would otherwise be heavily restricted by traditional relational database implementations. Apache Cassandra is an open-source application that is managed in a simple command line interface using the CQL language. CQL, or Cassandra Query Language is syntactically similar to the Structured Query Language, making it easy to pick up for those already familiar with SQL.
Install Cassandra
Add Repositories and GPG Keys
Add required repositories/gpg keys. Be sure to run the key add commands in the order shown.
Caution
(Ubuntu only) If you receive an error while running apt update that pertains to a missing key, copy the key listed in the error message and add it to your keyring using the commands in step 4. As of this publish date, the only keys required are listed below.
Ubuntu 17.04
1. Add the package software-properties-common:
apt install software-properties-common
2. Add the Java repository:
add-apt-repository ppa:webupd8team/java
3. Add the apache repository:
echo "deb http://www.apache.org/dist/cassandra/debian 39x main" | tee /etc/apt/sources.list.d/cassandra.list
Note:
You may want to follow the link to the Apache repository to confirm that “39x” is the latest available version.
4. Download the two public keys needed to access these repositories:
gpg --keyserver pgp.mit.edu --recv-keys 749D6EEC0353B12C gpg --export --armor 749D6EEC0353B12C | apt-key add - gpg --keyserver pgp.mit.edu --recv-keys A278B781FE4B2BDA gpg --export --armor A278B781FE4B2BDA | apt-key add -
CentOS 7
1. Install the “yum-utils” package:
yum install yum-utils -y
2. Add the Datastax repository:
yum-config-manager --add-repo http://rpm.datastax.com/community
3. Add the public key for the datastax repository. Create a directory for the downloaded key:
mkdir ~/.keys
4. Navigate to the “.keys” directory you just created and download the public key:
wget http://rpm.datastax.com/rpm/repo_key
5. The key should now be contained in a file called “repo_key”. Install the key with the package manager:
rpm --import repo_key
Install Cassandra and Supporting Applications
Update the system and install Java along with Cassandra. Answer “yes” to the Java installation prompts regarding the license terms (Ubuntu only). NTP will help keep the Cassandra node synced to the correct time.
Install Cassandra, Java, and NTP:
Ubuntu 17.04
apt-get update && apt-get upgrade -yuf apt-get install oracle-java8-set-default cassandra ntp -y
CentOS 7
yum update && yum upgrade -y yum install java dsc30 cassandra30-tools ntp -y
Activate Cassandra
1. Enable Cassandra on system boot and verify that it is running:
systemctl enable cassandra systemctl start cassandra systemctl -l status cassandra
2. Check the status of the Cassandra cluster:
nodetool status
If UN is displayed in the output, the cluster is working. Your output should resemble this:
Status=Up/Down |/ State=Normal/Leaving/Joining/Moving -- Address Load Tokens Owns (effective) Host ID Rack UN 127.0.0.1 103.51 KiB 256 100.0% c43a2db6-8e5f-4b5e-8a83-d9b6764d923d rack1
If you are receiving connection errors, open the cassandra-env.sh file in a text editor:
Ubuntu 17.04
vim /etc/cassandra/cassandra-env.sh
CentOS 7
vim /etc/cassandra/conf/cassandra-env.sh
Search for -Djava.rmi.server.hostname= in the file. Uncomment this line and add your loopback address or public IP address by replacing at the end of the line:
JVM_OPTS="$JVM_OPTS -Djava.rmi.server.hostname="
Restart Cassandra with systemctl restart Cassandra and check the node status nodetool status.
Note:
It may take a few seconds for Cassandra to refresh the configuration. If you receive another connection error, try waiting 15 seconds before rechecking the node status.
Configure Cassandra
Enable Security Features
1. Enable user login authentication. Make a backup of the Cassandra configuration file “cassandra.yaml.”
Note:
The CentOS 7 installation already includes a backup file located at /etc/cassandra/conf/cassandra.yaml.orig.
Ubuntu 17.04
cp /etc/cassandra/cassandra.yaml /etc/cassandra/cassandra.yaml.backup
2. Open “cassandra.yaml” in your preferred text editor:
Ubuntu 17.04
vim /etc/cassandra/cassandra.yaml
CentOS 7
vim /etc/cassandra/conf/cassandra.yaml
3. Match the following variables in the file to the values shown below. If any values are commented out, uncomment them. The rest of the properties found in the cassandra.yaml config file should be set based on your project’s particular requirements and how you plan to utilize Cassandra. The default configuration should work well for development.
More information on this file can be found by following the Cassandra .yaml Configuration File Overview link in the “External Resources” section.
After editing the file restart Cassandra.
Ubuntu /etc/cassandra/cassandra.yaml authenticator: org.apache.cassandra.auth.PasswordAuthenticator authorizer: org.apache.cassandra.auth.CassandraAuthorizer role_manager: CassandraRoleManager roles_validity_in_ms: 0 permissions_validity_in_ms: 0
Add An Administration Superuser
1. Open the Cassandra command terminal by typing cqlsh. Login with the credentials shown below for the default user “Cassandra”:
cqlsh -u cassandra -p cassandra
2. Create a new superuser. Replace the brackets as well as the content inside with the applicable information:
cassandra@cqlsh> CREATE ROLE [new_superuser] WITH PASSWORD = '[secure_password]' AND SUPERUSER = true AND LOGIN = true;
3. Log out by typing exit.
4. Log back in with the new superuser account using the new credentials, and remove the elevated permissions from the Cassandra account:
superuser@cqlsh> ALTER ROLE cassandra WITH PASSWORD = 'cassandra' AND SUPERUSER = false AND LOGIN = false; superuser@cqlsh> REVOKE ALL PERMISSIONS ON ALL KEYSPACES FROM cassandra;
5. Grant all permissions to the new superuser account. Replace the brackets and contents inside with your superuser account username:
superuser@cqlsh> GRANT ALL PERMISSIONS ON ALL KEYSPACES TO [superuser];
Edit The Console Configuration File
The cqlshrc file holds configuration settings that influence user preferences on how Cassandra performs certain tasks. Before proceeding, switch from the “root” user to your administrative Linux user account (you need sudo privileges for this).
Since your Cassandra username and password can be stored here in plaintext, this should only be accessible to your administrative user account, and is designed to be inaccessible to other accounts on your Linux system. Do not set this up as the root user. Caution: Before proceeding, fully evaluate the security risks and consequences to your node cluster before adding the [Authentication] section.
1. Create the file cqlshrc using your preferred text editor. If the ~/.cassandra directory does not exist, create it:
sudo mkdir ~/.cassandra sudo vim ~/.cassandra/cqlshrc
2. Copy any sections below that you wish to add to your configuration. Details for this file can be found by following the “Cassandra cqlshrc File Configuration Overview” link in the “External Resources” section.
Note:
CentOS 7 users can find a sample file containing all the configuration options at /etc/cassandra/conf/cqlshrc.sample.
.cassandra/cqlshrc ;; Options that are common to both COPY TO and COPY FROM [copy] ;; The string placeholder for null values nullval=null ;; For COPY TO, controls whether the first line in the CSV output file will ;; contain the column names. For COPY FROM, specifies whether the first ;; line in the CSV file contains column names. header=true ;; The string literal format for boolean values boolstyle = True,False ;; Input login credentials here to automatically login to the Cassandra command line without entering them each time. When this ;; is enabled, just type "cqlsh" to start Cassandra. [authentication] username=[superuser] password=[password] ;; Uncomment to automatically use a certain keyspace on login ;; keyspace=[keyspace] [ui] color=on datetimeformat=%Y-%m-%d %H:%M:%S%z completekey=tab ;; The number of digits displayed after the decimal point ;; (note that increasing this to large numbers can result in unusual values) float_precision = 5 ;; The encoding used for characters encoding = utf8
3. Save and close the file. Update the file and directory with the following permissions:
sudo chmod 1700 ~/.cassandra/cqlshrc
sudo chmod 700 ~/.cassandra
If you enabled the auto-login feature, login by typing cqlsh. The command terminal should open, and your superuser name should be visible in the command line.
Rename the Cluster
Update your default cluster name from “Test Cluster” to your desired name.
1. Login to the control terminal with cqlsh. Replace [new_name] with your new cluster name:
UPDATE system.local SET cluster_name = '[new_name]' WHERE KEY = 'local';
2. Edit the cassandra.yaml file and replace the value in the cluster_name variable with the new cluster name you just set.
3. Save and close.
Ubuntu 17.04
vim /etc/cassandra/cassandra.yaml
CentOS 7
vim /etc/cassandra/conf/cassandra.yaml
4. From the Linux terminal (not cqlsh), run nodetool flush system. This will clear the system cache and preserve all data in the node.
5. Restart Cassandra. Log in with cqlsh and verify the new cluster name is visible.
