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Cassandra Quick Start

Posted by Kylin Soong on Feb 4, 2017 categorized as data

This article contain Cassandra quick installation, basic commands of create keyspace and table, and a samples for how Java Application connect to Cassandra.

Quick installation

Install cassandra 2.x to RHEL

Download one of stable version from http://archive.apache.org/dist/cassandra/, for example 2.0.1. Installing via unzip:

tar -xvf apache-cassandra-2.0.1-bin.tar.gz

Start Cassandra via invoking ‘bin/cassandra -f’.

Edit conf/cassandra.yaml, change rpc_address from localhost to a IP address,

rpc_address: 10.66.218.46

this is necessary for remote connect.

Install cassandra 3.9 to RHEL

  • Download cassandra from http://cassandra.apache.org/
wget http://mirrors.ibiblio.org/apache/cassandra/3.9/apache-cassandra-3.9-bin.tar.gz
  • Install Cassandra via extract tar file
tar -xvf apache-cassandra-3.9-bin.tar.gz
  • Edit conf/cassandra.yaml, change rpc_address from localhost to a IP address,
rpc_address: 10.66.192.120
  • Change into the cassandra home, start cassandra via
./bin/cassandra -f

create a keyspace and table

bin/cqlsh is an interactive command line interface for Cassandra. cqlsh allows you to execute CQL (Cassandra Query Language) statements against Cassandra. Run the following command to connect to your local Cassandra instance with cqlsh:

$ bin/cqlsh
  • To create the keyspace “demo”, at the CQL shell prompt, type:
cqlsh> CREATE KEYSPACE demo WITH REPLICATION = { 'class' : 'SimpleStrategy', 'replication_factor' : 1 };
  • To use the keyspace we’ve just created, type:
cqlsh> USE demo;
  • Create a “users” table within the keyspace “demo” so that we can insert some data into our database:
cqlsh> CREATE TABLE users (
firstname text,
lastname text,
age int,
email text,
city text,
PRIMARY KEY (lastname));
  • Type ENTER after each statement to insert the row into the table:
cqlsh:demo> INSERT INTO users (firstname, lastname, age, email, city) VALUES ('John', 'Smith', 46, 'johnsmith@email.com', 'Sacramento');
cqlsh:demo> INSERT INTO users (firstname, lastname, age, email, city) VALUES ('Jane', 'Doe', 36, 'janedoe@email.com', 'Beverly Hills');
cqlsh:demo> INSERT INTO users (firstname, lastname, age, email, city) VALUES ('Rob', 'Byrne', 24, 'robbyrne@email.com', 'San Diego');
  • Now that we have a few rows of data in our table, let’s perform some queries against it. Using a SELECT statement will let us take a peek inside our table. To see all the rows from the users table we’ve created, type:
cqlsh:demo> SELECT * FROM users;
  • Get the user record for the individual with the last name “Doe”
cqlsh:demo> SELECT * FROM users WHERE lastname= 'Doe';
  • We can delete a row of data using the DELETE command:
cqlsh:demo> DELETE from users WHERE lastname = “Doe”;

An example of using Datastax Java Driver

Add Maven Driver dependency

<dependency>
    <groupId>com.datastax.cassandra</groupId>
    <artifactId>cassandra-driver-core</artifactId>
    <version>3.1.3</version>
</dependency>

Build a Cluster

Cluster cluster = Cluster.builder()
        .addContactPoint("10.66.192.120")
        .withPort(9042)
        .withCredentials("user", "password")
        .build();

Metadata

Metadata metadata = cluster.getMetadata();
System.out.println(metadata.getClusterName());
metadata.getKeyspaces().forEach(km -> {
    System.out.println(km.getName());
    km.getTables().forEach(t -> System.out.println("    " + t.getName() + ", " + t.getId()));
});

NOTE: This will print Keyspaces and the tables, by default Cassandra contains Keyspaces: system_traces, system, system_distributed, system_schema, system_auth.

Session with DML

Session session = cluster.connect("demo");

Insert

sql = "INSERT INTO users (lastname, age, city, email, firstname) VALUES ('Soong', 29, 'Beijing', 'ksoong@redhat.com', 'Kylin')";
session.execute(sql);

Select

sql = "SELECT * FROM users";
ResultSet results = session.execute(sql);
results.forEach(row -> System.out.format("    %s %d\n", row.getString("firstname"),row.getInt("age")));

Delete

sql = "DELETE FROM users WHERE lastname = 'Soong'";
session.execute(sql);

ProtocolVersion

ProtocolVersion version = session.getCluster().getConfiguration().getProtocolOptions().getProtocolVersion();
System.out.println(version);

Executing Batch

List<String> updates = new ArrayList<String>();
updates.add("INSERT INTO users (lastname, age, city, email, firstname) VALUES ('Soong', 30, 'Beijing', 'ksoong@redhat.com', 'Kylin')");

BatchStatement bs = new BatchStatement();
updates.forEach(update -> bs.add(new SimpleStatement(update)));
session.executeAsync(bs);

Executing Batch with bindng values

List<Object[]> values = new ArrayList<>();
values.add(new Object[]{"Soong", 30, "Beijing", "ksoong@redhat.com", "Kylin"});
sql = "INSERT INTO users (lastname, age, city, email, firstname) VALUES (?, ?, ?, ?, ?)";
PreparedStatement ps = session.prepare(sql);
values.forEach(v -> {
    BoundStatement bound = ps.bind(v);
    bs.add(bound);
});
session.executeAsync(bs);