Install Cassandra (Standalone) on CentOS 6x

Install Cassandra (Standalone) on CentOS 6x ==================================================

Step: 1. Install JAVA :

# cd /tmp
# wget --no-check-certificate --no-cookies --header 'Cookie: oraclelicense=accept-securebackup-cookie' http://download.oracle.com/otn-pub/java/jdk/8u5-b13/jdk-8u5-linux-x64.rpm
# yum -y install jdk-8u5-linux-x64.rpm
# export JAVA_HOME=/usr/java/jdk1.8.0_05
# export PATH=$PATH:$JAVA_HOME
# echo $JAVA_HOME
# vi /etc/profile.d/java.sh

#!/bin/bash
JAVA_HOME=/usr/java/jdk1.8.0_05
PATH=$JAVA_HOME/bin:$PATH
export PATH JAVA_HOME
export CLASSPATH=.

-- Save & Quit (:wq)

chmod +x /etc/profile.d/java.sh
source /etc/profile.d/java.sh
Step: 2. Install the Java Native Access (JNA) :

# yum -y install jna
Step: 3. Add a symbolic link to the Oracle Java SE Runtime Environment 7 installation :

alternatives --install /usr/bin/java java /usr/java/jdk1.8.0_05/bin/java 20000
Step: 4. Then use the alternatives command to verify that the Oracle Java SE Runtime Environment 8 is selected :

alternatives --config java
Selection Command
-----------------------------------------------
+ 1 /usr/lib/jvm/jre-1.7.0-openjdk.x86_64/bin/java
2 /usr/lib/jvm/jre-1.6.0-openjdk.x86_64/bin/java
3 /usr/java/jdk1.8.0_05/bin/java

Enter to keep the current selection[+], or type selection number: 3

Step: 5. Verify Java Version :

java -version
Step: 6. Add the DataStax Community Repository :

vi /etc/yum.repos.d/datastax.repo
[datastax]
name = DataStax Repo for Apache Cassandra
baseurl = http://rpm.datastax.com/community
enabled = 1
gpgcheck = 0

-- Save & Quit (:wq)

Step: 7. Install Apache Cassandra 2 :

yum -y install dsc20
Step: 8. Configure the Apache Cassandra 2 Environment :

export JAVA_HOME=/usr/java/jdk1.8.0_05/
export PATH=$PATH:/usr/java/jdk1.8.0_05/bin/
Step: 9. Get Cassandra Running :

service cassandra start
chkconfig cassandra on
Step: 10. Enter the Cassandra Command Line

cqlsh
The HELP command displays a synopsis & a brief description of all cqlsh commands. Given below is the usage of help command.

cqlsh> help

Documented shell commands: ===========================
CAPTURE COPY DESCRIBE EXPAND SHOW TRACING
CONSISTENCY DESC EXIT HELP SOURCE

CQL help topics: ================
ALTER CREATE_TABLE_OPTIONS SELECT
ALTER_ADD CREATE_TABLE_TYPES SELECT_COLUMNFAMILY
ALTER_ALTER CREATE_USER SELECT_EXPR
ALTER_DROP DELETE SELECT_LIMIT
ALTER_RENAME DELETE_COLUMNS SELECT_TABLE
ALTER_USER DELETE_USING SELECT_WHERE
ALTER_WITH DELETE_WHERE TEXT_OUTPUT
APPLY DROP TIMESTAMP_INPUT
ASCII_OUTPUT DROP_COLUMNFAMILY TIMESTAMP_OUTPUT
BEGIN DROP_INDEX TRUNCATE
BLOB_INPUT DROP_KEYSPACE TYPES
BOOLEAN_INPUT DROP_TABLE UPDATE
COMPOUND_PRIMARY_KEYS DROP_USER UPDATE_COUNTERS
CREATE GRANT UPDATE_SET
CREATE_COLUMNFAMILY INSERT UPDATE_USING
CREATE_COLUMNFAMILY_OPTIONS LIST UPDATE_WHERE
CREATE_COLUMNFAMILY_TYPES LIST_PERMISSIONS USE
CREATE_INDEX LIST_USERS UUID_INPUT
CREATE_KEYSPACE PERMISSIONS
CREATE_TABLE REVOKE

In Cassandra, a keyspace is a container for your application data. It is similar to the schema in a relational database.

cqlsh> desc keyspaces;

system system_traces

Step: 11. To create the keyspace "demo", at the CQL shell prompt, type :

cqlsh> create keyspace demo
WITH REPLICATION = { 'class' : 'SimpleStrategy', 'replication_factor' : 1 };

cqlsh> desc keyspaces;

system system_traces demo

cqlsh> use demo;

cqlsh:demo>

Now we have we have a keyspace, we can create tables within that keyspace to store our data in. Tables, or column families,
consist of columns and rows.

Step: 12. Create a “users” table within the keyspace “demo” so that we can insert some data into our database :

cqlsh> USE demo;

cqlsh:demo> create table users ( firstname text,lastname text,age int,city text,primary key (lastname));

cqlsh:demo> DESC SCHEMA;

CREATE KEYSPACE demo WITH replication = {
'class': 'SimpleStrategy',
'replication_factor': '1'
};

USE demo;

CREATE TABLE users (
lastname text,
age int,
city text,
firstname text,
PRIMARY KEY ((lastname))
) WITH
bloom_filter_fp_chance=0.010000 AND
caching='KEYS_ONLY' AND
comment='' AND
dclocal_read_repair_chance=0.100000 AND
gc_grace_seconds=864000 AND
index_interval=128 AND
read_repair_chance=0.000000 AND
replicate_on_write='true' AND
populate_io_cache_on_flush='false' AND
default_time_to_live=0 AND
speculative_retry='99.0PERCENTILE' AND
memtable_flush_period_in_ms=0 AND
compaction={'class': 'SizeTieredCompactionStrategy'} AND
compression={'sstable_compression': 'LZ4Compressor'};

Step: 13. Insert some rows of Data into our newly created ‘users’ table :

Type ENTER after each statement to insert the row into the table:

cqlsh:demo> INSERT INTO users (firstname, lastname, age,city) values ('Soumya', 'Das', 30, 'Calcutta');
cqlsh:demo> INSERT INTO users (firstname, lastname, age,city) values ('udit', 'Gujar', 24, 'Pune');

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;

lastname     | age | city    | firstname
--------------+-----+---------+-----------
   das          |  30 | Calcutta| soumya
   Gujar      |  24 |  Pune   | Udit
(2 rows)

cqlsh:demo> exit

Step: 14. Check Cassandra Node Status :

nodetool status
Step: 15. Shutdown Cassandra :

service cassandra stop
service cassandra status
Done...!!!




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Master-Slave replication on PostgreSQL on Rhel/Centos 6.5

Master server:-192.168.100.122
Hostname:-server2.soumya.com

Slave server:-192.168.100.175
Hostname:-server1.soumya.com

Postgresql Version:9.4-1
Linux version:Rhel 6.3


Install postgresql in both server:-
Step 1:-Download the repository
yum install http://yum.postgresql.org/9.4/redhat/rhel-6-x86_64/pgdg-centos94-9.4-1.noarch.rpm

# vi /etc/yum.repos.d/centos.repo
add the following lines
[centos-6-base]
name=CentOS-$releasever - Base
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os
baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/
enabled=1


step 2:- Install Postgresql required packages:-
# yum install postgresql94-server postgresql94-contrib
Incase if the above command gives error regarding the public key, we can use the following command
cd /etc/pki/rpm-gpg
rpm --import RPM-GPG-KEY-CentOS-6

#yum install postgresql94-server

# service postgresql-9.4 initdb

OR

# service postgresql initdb

# chkconfig postgresql-9.4 on

Step 3:-Start postgresql:-

[root@infosystem ~]# service postgresql-9.4 start
Starting postgresql service: [  OK  ]

Check status of postgresql:-
[root@infosystem ~]# service postgresql status
postmaster (pid  4260) is running...

Step 4:- Perform this in both server:-

PostgreSQL creates a user called "postgres" in order to handle its initial databases.
We will configure ssh access between our servers to make transferring files easier.

#passwd postgres
login to postgres user

#su - postgres

Generate an ssh key for the postgres user:(Do this is both server)
In Master server:-
$ ssh-keygen -t rsa
$ ssh-keygen -t dsa
$ cd /var/lib/pgsql/.ssh
$ cat id_rsa.pub >>authorized_keys
$ cat id_dsa.pub >>authorized_keys


In Slave server:-
$ ssh-keygen -t rsa
$ ssh-keygen -t dsa
$ cd /var/lib/pgsql/.ssh
$ cat id_rsa.pub >>authorized_keys
$ cat id_dsa.pub >>authorized_keys


In Master server:-
$ cd /var/lib/pgsql/.ssh
$ cp authorized_keys server2_authorized_keys
$ scp server2_authorized_keys postgres@server1:/var/lib/pgsql/
$ rm -rf authorized_keys

In slave server:-
$ cd /var/lib/pgsql/.ssh
$ cat server2_authorized_keys >>authorized_keys
$ scp authorized_keys postgres@server2:/var/lib/pgsql/

Now test the connectivity from both server.
From master server:-
ssh server1 date

From slave server:-
ssh server2 date

Step 5:-Configure the Master Server.

# su - postgres

$ psql -c "CREATE USER rep REPLICATION LOGIN CONNECTION LIMIT 1 ENCRYPTED PASSWORD 'redhat';"

Next, we will move to the postgres configuration directory:
$ cd /var/lib/pgsql/9.4/data

At any place not at the bottom of the file, add a line to let the new user get access to this server:
$ vi pg_hba.conf

host    replication     rep     192.168.100.175/32   md5

:wq

Next, open the main postgres configuration file:

$ vi postgresql.conf

Find these parameters. Uncomment them if they are commented, and modify the values according to what we have listed below:

listen_addresses = 'localhost,192.168.100.122'
wal_level = 'hot_standby'
archive_mode = on
archive_command = 'cd .'
max_wal_senders = 1
hot_standby = on
Save and close the file.


Restart the master server to implement your changes from root user:-
# service  postgresql-9.4 restart

Step 6.Configure the Slave Server.

Begin on the slave server by shutting down the postgres database software:

# service postgresql-9.4 stop


On the slave server, We then will transfer the database data from master server:-

$ cd /var/lib/pgsql/9.4/data
$ rm -rf *
$ pg_basebackup -D /var/lib/pgsql/9.4/data -h 192.168.100.122 -U rep

Now we can see all the files from the master server has been copied into the slave server.

We will be making some similar configuration changes to postgres files,
so change to the configuration directory:

# su - postgres
$ cd /var/lib/pgsql/9.4/data


Adjust the access file to allow the other server to connect to this.
This is in case we need to turn the slave into the master later on down the road.

$ vi pg_hba.conf

Again, add this line somewhere not at the end of the file:

host    replication     rep     192.168.100.122/32  md5

Save and close the file.

Next, open the postgres configuration file:

$ vi postgresql.conf

You can use the same configuration options you set for the master server, modifying only the IP address
to reflect the slave server's address:

listen_addresses = 'localhost,192.168.100.175'
wal_level = 'hot_standby'
archive_mode = on
archive_command = 'cd .'
max_wal_senders = 1
hot_standby = on


--Save and exit.

Step 7.Create recovery.conf file

Here, we need to create a recovery file called recovery.conf:
$ cd /var/lib/pgsql/9.4/data
$ vi recovery.conf

standby_mode = 'on'
primary_conninfo = 'host=192.168.100.122 port=5432 user=rep password=redhat'
trigger_file = '/tmp/postgresql.trigger.5432'

--save and exit.

Test the replication:-
On Master server:-
$ su - postgres
$psql
#CREATE TABLE rep_test (test varchar(40));
Now, we can insert some values into the table with the following commands:

INSERT INTO rep_test VALUES ('data one');
INSERT INTO rep_test VALUES ('some more words');
INSERT INTO rep_test VALUES ('lalala');
INSERT INTO rep_test VALUES ('hello there');
INSERT INTO rep_test VALUES ('blahblah');
To exit from psql shell
\q

Now on slave server:-
$ su - postgres
$psql
#SELECT * FROM rep_test;

      test    
-----------------
 data one
 some more words
 lalala
 hello there
 blahblah
(5 rows)

Now lets see if try insert data from slave server :-

#INSERT INTO rep_test VALUES ('oops');
ERROR:  cannot execute INSERT in a read-only transaction

As we can see, we are unable to insert data into the slave. This is because the data is only being
transferred in one direction. In order to keep the databases consistent, postgres must make the slave
read-only.




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