Cassandra#

Just some free format stuff for a small studying / experiment with NoSQL stuff.

Resources#

• C* 2012: Building a Cassandra Based Application from Scratch (Patrick McFadin, Hobsons)
• Introduction to NoSQL by Martin Fowler
• http://cassandra.apache.org/
• Datastax Documentation

Install/config#

lxc#

• /etc/default/lxc => change subnet from 10.0.3 to 10.0.4 (10.0.3 is already in use somewhere else)
• add static route in wireless router (10.0.4.0/8 => via 10.0.0.164)
• adjust /etc/network/interfaces of container to:

auto eth0
#iface eth0 inet dhcp
iface eth0 inet static
        address 10.0.4.10
        netmask 255.255.255.0
        network 10.0.4.0
        broadcast 10.0.4.255
        gateway 10.0.4.1
        post-up route add default gw 10.0.4.1 dev eth0
        # dns-* options are implemented by the resolvconf package, if installed
        dns-nameservers 213.197.28.3 213.197.30.28
        dns-search computerhok.nl

• lxc-host ubuntu1 => 10.0.4.11 (user=ubuntu, password=ubuntu)

cassandra#

• useradd cssndra && mkdir /home/cssndra && chown -R cssndra /home/cssndra + change /etc/passwd => sh => bash
• wget 'http://mirrors.supportex.net/apache/cassandra/1.2.4/apache-cassandra-1.2.4-bin.tar.gz'
• apt-get install openjdk-7-jdk
• sudo mkdir /opt/apache-cassandra-1.2.4 && sudo chown cssndra /opt/apache-cassandra-1.2.4 && sudo ln -s /opt/apache-cassandra-1.2.4 /opt/cassandra
• cssndra@ubuntu1:~$ cd /opt && tar -xf ~/apache-cassandra-1.2.4-bin.tar
• ls -l

cssndra@ubuntu1:/opt/cassandra$ ls -l
total 248
-rw-r--r-- 1 cssndra cssndra 152928 Apr  8 19:21 CHANGES.txt
-rw-r--r-- 1 cssndra cssndra  11609 Apr  8 19:21 LICENSE.txt
-rw-r--r-- 1 cssndra cssndra  47580 Apr  8 19:21 NEWS.txt
-rw-r--r-- 1 cssndra cssndra   1820 Apr  8 19:21 NOTICE.txt
-rw-r--r-- 1 cssndra cssndra   3569 Apr  8 19:21 README.txt
drwxr-xr-x 2 cssndra cssndra   4096 May 15 21:43 bin
drwxr-xr-x 2 cssndra cssndra   4096 May 15 21:43 conf
drwxr-xr-x 2 cssndra cssndra   4096 May 15 21:43 interface
drwxr-xr-x 4 cssndra cssndra   4096 May 15 21:43 javadoc
drwxr-xr-x 3 cssndra cssndra   4096 May 15 21:43 lib
drwxr-xr-x 3 cssndra cssndra   4096 May 15 21:43 pylib
drwxr-xr-x 4 cssndra cssndra   4096 Apr  8 19:21 tools

• sudo mkdir -p /var/lib/cassandra/data /var/lib/cassandra/commitlog && sudo chown -R cssndra /var/lib/cassandra
• sudo mkdir /var/log/cassandra/ && sudo chown -R cssndra /var/log/cassandra
• limit the heap size usage by editing conf/cassandra-env.sh : MAX_HEAP_SIZE="512M" HEAP_NEWSIZE="100M"
• edit ./conf/cassandra.yaml:
  • change the listen_address to 10.0.4.11 , necessary for multinode cluster communication (as OS hostname/ip is not properly configured)
  • change the rpc_address to 10.0.4.11 , necessary to make it reachable from non-localhost (as OS hostname/ip is not properly configured)
  • change the seeds parameter from 127.0.0.1 to 10.0.4.11 (this first node becomes the seed node for all nodes)
• ==> now first clone the VM : lxc-clone -o ubuntu1 -n ubuntu2 , ubuntu2 has address 10.0.4.12
• continue with the first node and there start the thing with : ./bin/cassandra -f
• add keyspace:

Now on the second node (ubuntu2) start the node with /opt/cassandra/bin/cassandra , and start creating the cluster. First create the proper tokens for a 4 node cluster, by using the following py :

# Number of nodes in the cluster
num_node = 4

for n in range(num_node):
    print int(2**127 / num_node * n)

cssndra@ubuntu1:~$ python calcToken.py 
0
42535295865117307932921825928971026432
85070591730234615865843651857942052864
127605887595351923798765477786913079296

First startup cassandra on all 4 nodes by executing from the host: ssh ubuntu@10.0.4.11 'sudo su - cssndra /opt/cassandra/bin/cassandra'

Cluster config#

Cassandra notes/questions#

Questions#

• Can I share a cassandra cluster between multiple applications while still having some form of (security) separation ? (like having multiple databases in MySQL, and arranging access to them with grants).
• Security in general, how is the gossip protected, how to prevent "illegal nodes" from entering the cluster ?
• Security, how is access control arranged, and on what level ?
• How to change replica settings ?
  • You set the number of replicas when you create a keyspace using the replica placement strategy.
  • run through cqlsh: ALTER KEYSPACE "Excalibur" WITH REPLICATION = { 'class' : 'SimpleStrategy', 'replication_factor' : 3 };
  • On each affected node, run nodetool repair. Wait until repair completes on a node before moving to the next node.
  • also see http://www.datastax.com/docs/1.2/cql_cli/using/keyspace
• How to take down (phase out) a node in a controlled way ?
• what snitch to use ?

Notes#

• Every node should have the same list of seeds. In multiple data-center clusters, the seed list should include a node from each data center.
• Use NetworkTopologyStrategy when you have (or plan to have) your cluster deployed across multiple data centers