Cassandra

The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.

https://docs.datastax.com/en/cql/3.3/cql/ddl/dataModelingApproach.html Because Cassandra uses this single table-single query approach, queries can perform faster. Data in Cassandra is often arranged as one query per table, and data is repeated in many tables, a process known as denormalization.

Slackbuild

• cd /tmp

• wget http://slackbuilds.org/slackbuilds/14.1/system/apache-cassandra.tar.gz

• tar xvzf apache-cassandra.tar.gz

• wget http://archive.apache.org/dist/cassandra/2.0.7/apache-cassandra-2.0.7-bin.tar.gz

• ./apache-cassandra.SlackBuild

• installpkg /tmp/apache-cassandra-2.0.7-noarch-1_SBo.tgz

Node up

• useradd cassandra
• mkdir /home/cassandra
• cd /home/cassandra
• chown cassandra . -R
• mkdir /var/lib/cassandra
• cd /var/lib/cassandra
• chown cassandra . -R
• mkdir /var/log/cassandra
• cd /var/log/cassandra
• chown cassandra . -R
• JAVA_HOME=/opt/java /opt/apache-cassandra/bin/cassandra -f

cqlsh

http://wiki.apache.org/cassandra/GettingStarted

• bin/cqlsh

CREATE KEYSPACE mykeyspace WITH REPLICATION = { 'class' : 'SimpleStrategy', 'replication_factor' : 1 };
describe keyspaces;
USE mykeyspace;
CREATE TABLE users (  user_id int PRIMARY KEY,  fname text,  lname text );
INSERT INTO users (user_id,  fname, lname)  VALUES (1745, 'john', 'smith');
INSERT INTO users (user_id,  fname, lname)  VALUES (1744, 'john', 'doe');
INSERT INTO users (user_id,  fname, lname)  VALUES (1746, 'john', 'smith');
describe tables;
SELECT * FROM users;
desc table users;
CREATE INDEX ON users (lname);
desc table users;
SELECT * FROM users WHERE lname = 'smith';

Python sample app

http://datastax.github.io/python-driver/getting_started.html

• cd /tmp/

• wget http://slackbuilds.org/slackbuilds/14.1/libraries/libev.tar.gz

• tar xvzf libev.tar.gz
• cd libev

• wget http://dist.schmorp.de/libev/Attic/libev-4.15.tar.gz

• ./libev.SlackBuild

• installpkg /tmp/libev-4.15-i486-2_SBo.tgz
• easy_install pip # if not installed
• pip install cassandra-driver
• pip install blist

python3 cass.py

   1 from cassandra.cluster import Cluster
   2 
   3 cluster = Cluster(['127.0.0.1'])
   4 session = cluster.connect('mykeyspace')
   5 rows = session.execute('SELECT  user_id , fname , lname FROM users')
   6 for user_row in rows:
   7     print('%d %s %s'%( user_row.user_id, user_row.fname, user_row.lname) )

python3 asyncCass.py

   1 import time
   2 from cassandra.cluster import Cluster
   3 
   4 def sucessHandler(rows):
   5     print('Received data !')
   6     try:
   7         for user_row in rows:
   8             print('>>> %d %s %s'%( user_row.user_id, user_row.fname, user_row.lname) )
   9     except Exception as ex:
  10         print(ex) 
  11 
  12 def errorHandler(exception):
  13     print(exception) 
  14 
  15 if __name__=='__main__':
  16     cluster = Cluster(['127.0.0.1'])
  17     session = cluster.connect('mykeyspace')
  18     futurex = session.execute_async('SELECT  user_id , fname , lname FROM users')
  19     futurex.add_callbacks(sucessHandler,errorHandler)
  20     print('Wait 3 seconds ...')
  21     time.sleep(3)

Python types conversion

http://datastax.github.io/python-driver/getting_started.html

Java types conversion

http://www.datastax.com/documentation/developer/java-driver/2.0/java-driver/reference/javaClass2Cql3Datatypes_r.html

Export and import schema

• echo -e "use schema;\nDESCRIBE KEYSPACE;\n" | cqlsh CassandraHost > mySchema.cdl

• cqlsh CassandraNEWhost -f mySchema.cdl