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Creating a Multi-node Cassandra Cluster on Centos 6.5.

Creating a Multi-node Cassandra Cluster on Centos 6.5.

Table of Contents

This is a basic multi-node cassandra setup.

Initial Server Setup

Hardware Information

All the server were with below configuration.
CPU : 40 Cores
RAM : 192GB

Setting Host for cassandra

Setting up the servers and update /etc/hosts as below.
#Adding CASSANDRA NODES
10.10.18.35    CASSANDRA01      #SEED
10.10.18.93    CASSANDRA02      #Worker
10.10.18.98    CASSANDRA03      #Worker

Updating hostname on all servers.

Update hostnames as required.
sudo vim /etc/sysconfig/network
Update hostname as below, do the same in all servers [CASSANDRA01, CASSANDRA02,CASSANDRA03].
NETWORKING=yes
HOSTNAME=CASSANDRA01
To update the hostname without a reboot execute below command.
sudo hostname CASSANDRA01
NOTE : hostname command will keep the hostname till the next reboot. So its required that we update/etc/sysconfig/network file.

Creating cassandra user with sudo permissions.

Have a script which will create a user on server.
wget https://raw.githubusercontent.com/zubayr/create_user_script/master/create_user_script.sh
sh create_user_script.sh -s cassandra
This will create a cassendra user, with sudo permissions.

Creating passwordless entry from SEED (CASSANDRA01) to other servers.

Create a rsa key on CASSANDRA01
ssh-keygen -t rsa
Create .ssh directory on other 2 servers.
ssh cassandra@CASSANDRA02 mkdir -p .ssh
ssh cassandra@CASSANDRA03 mkdir -p .ssh
Add the id_rsa.pub to authorized_keys
cat ~/.ssh/id_rsa.pub | ssh cassandra@CASSANDRA02 'cat >> .ssh/authorized_keys'
cat ~/.ssh/id_rsa.pub | ssh cassandra@CASSANDRA03 'cat >> .ssh/authorized_keys'
Make sure we have the right permissions.
ssh cassandra@CASSANDRA02 chmod 744 -R .ssh 
ssh cassandra@CASSANDRA03 chmod 744 -R .ssh
Testing.
ssh cassandra@CASSANDRA02
ssh cassandra@CASSANDRA03

Extracting Files.

Extracting Files to opt and creating a link.
sudo tar xvzf apache-cassandra-2.1.3-bin.tar.gz -C /opt
sudo ln -s /opt/apache-cassandra-2.1.3 /opt/cassandra
sudo chown cassandra:cassandra -R /opt/cassandra
sudo chown cassandra:cassandra -R /opt/apache-cassandra-2.1.3
Creating Required Directories.
sudo mkdir -p /data1/cassandra/commitlog
sudo mkdir -p /data1/cassandra/data
sudo mkdir -p /data1/cassandra/saved_cahes

Updating Configuration File.

Setting initial_token as below.

Node 0: 0 Node 1: 3074457345618258602 Node 2: 6148914691236517205

On Node CASSANDRA01

cluster_name: 'MyCassandraCluster'
initial_token: 0
seed_provider:
  - class_name: org.apache.cassandra.locator.SimpleSeedProvider
    parameters:
         - seeds: "10.10.18.35"
listen_address: 10.10.18.35
endpoint_snitch: SimpleSnitch

data_file_directories:
    - /data1/cassandra/data

commitlog_directory: /data1/cassandra/commitlog
saved_caches_directory: /data1/cassandra/saved_caches

On Node CASSANDRA02

cluster_name: 'MyCassandraCluster'
initial_token: 3074457345618258602
seed_provider:
  - class_name: org.apache.cassandra.locator.SimpleSeedProvider
    parameters:
         - seeds: "10.10.18.35"
listen_address: 10.10.18.93
endpoint_snitch: SimpleSnitch

data_file_directories:
    - /data1/cassandra/data

commitlog_directory: /data1/cassandra/commitlog
saved_caches_directory: /data1/cassandra/saved_caches

On Node CASSANDRA03

cluster_name: 'MyCassandraCluster'
initial_token: 6148914691236517205
seed_provider:
  - class_name: org.apache.cassandra.locator.SimpleSeedProvider
    parameters:
         - seeds: "10.10.18.35"
listen_address: 10.10.18.98
endpoint_snitch: SimpleSnitch

data_file_directories:
    - /data1/cassandra/data

commitlog_directory: /data1/cassandra/commitlog
saved_caches_directory: /data1/cassandra/saved_caches

Starting cassandra.

On Server CASSANDRA01.
sh /opt/cassandra/bin/cassandra
Wait till the server initialize and then start rest of nodes.
On Server CASSANDRA02.
sh /opt/cassandra/bin/cassandra
On Server CASSANDRA03.
sh /opt/cassandra/bin/cassandra

Checking Cluster Information.

[cassandra@CASSANDRA01 bin]$ ./nodetool status
Datacenter: datacenter1
=======================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
--  Address       Load       Tokens  Owns (effective)  Host ID                               Rack
UN  10.10.18.98  72.09 KB   1       33.3%             1a5a0c77-b5e6-4057-87b4-a8e788786244  rack1
UN  10.10.18.35  46.24 KB   1       83.3%             67de1b1f-8070-48c1-ad88-2c0d4dd7a988  rack1
UN  10.10.18.93  55.64 KB   1       83.3%             7fba7cd0-6f99-4ce8-8194-c9a8b23488cd  rack1

Logging into CQL Shell.

We need to export CQLSH_HOST
[cassandra@CASSANDRA01 bin]$ export CQLSH_HOST=10.10.18.35
[cassandra@CASSANDRA01 bin]$ cqlsh
Connected to CassandraJIOCluster at 10.10.18.35:9042.
[cqlsh 5.0.1 | Cassandra 2.1.3 | CQL spec 3.2.0 | Native protocol v3]
Use HELP for help.
cqlsh>

Data Location on CASSANDRA01, CASSANDRA02, CASSANDRA03

[cassandra@CASSANDRA01 bin]$ ls -l /data1/cassandra/
total 12
drwxr-xr-x 2 cassandra cassandra 4096 Mar 19 14:23 commitlog
drwxr-xr-x 4 cassandra cassandra 4096 Mar 19 14:23 data
drwxr-xr-x 2 cassandra cassandra 4096 Mar 19 13:18 saved_caches
[cassandra@CASSANDRA01 bin]$

Performace Tuning.

Updating cassandra.yaml file.

# For workloads with more data than can fit in memory, Cassandra's
# bottleneck will be reads that need to fetch data from
# disk. "concurrent_reads" should be set to (16 * number_of_drives) in
# order to allow the operations to enqueue low enough in the stack
# that the OS and drives can reorder them. Same applies to
# "concurrent_counter_writes", since counter writes read the current
# values before incrementing and writing them back.
#
# On the other hand, since writes are almost never IO bound, the ideal
# number of "concurrent_writes" is dependent on the number of cores in
# your system; (8 * number_of_cores) is a good rule of thumb.

#concurrent_reads: 32
#concurrent_writes: 32

# Change as we had a 40core machine which calculates to 240.
concurrent_reads: 32
concurrent_writes: 240
concurrent_counter_writes: 32

Updating cassandra-env.sh file.

# Override these to set the amount of memory to allocate to the JVM at
# start-up. For production use you may wish to adjust this for your
# environment. MAX_HEAP_SIZE is the total amount of memory dedicated
# to the Java heap; HEAP_NEWSIZE refers to the size of the young
# generation. Both MAX_HEAP_SIZE and HEAP_NEWSIZE should be either set
# or not (if you set one, set the other).
#
# The main trade-off for the young generation is that the larger it
# is, the longer GC pause times will be. The shorter it is, the more
# expensive GC will be (usually).
#
# The example HEAP_NEWSIZE assumes a modern 8-core+ machine for decent pause
# times. If in doubt, and if you do not particularly want to tweak, go with
# 100 MB per physical CPU core.

# Important is the HEAP_NEWSIZE 100MB * number of Core (40 cores in our case)

#MAX_HEAP_SIZE="4G"
#HEAP_NEWSIZE="800M"
MAX_HEAP_SIZE="15G"
HEAP_NEWSIZE="4G"

Updating cassandra-topology.properties file.

If the server are in Data Center which in different location then we need to update this file as well. Also specify rack in that DC.
Cassandra
{{Node IP}}={{Data Center}}:{{Rack}}.
NOTE : This has to match with the cassendra-rackdc.properties file.
10.10.18.35=DC1:RAC1
10.10.18.93=DC2:RAC1
10.10.18.98=DC2:RAC2
When using this format we need to update cassendra-rackdc.properties and use endpoint_snitch: asGossipingPropertyFileSnitch in the cassandra.yaml

Useful Links

https://www.digitalocean.com/community/tutorials/how-to-configure-a-multi-node-cluster-with-cassandra-on-a-ubuntu-vps
https://www.datastax.com/documentation/cassandra/1.2/cassandra/initialize/initializeSingleDS.html
http://www.rackspace.com/knowledge_center/article/centos-hostname-change
http://www.datastax.com/documentation/cassandra/2.0/cassandra/initialize/initializeSingleDS.html
http://www.datastax.com/documentation/cassandra/2.1/cassandra/configuration/configCassandra_yaml_r.html
http://whatizee.blogspot.in/2013/12/passwordless-login-from-ahmedamd-to.html?q=passwordless
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