Jun 222016
 

Intro

Cassandra is highly available (no SPOF) distributed database service for managing large amounts of structured data across many commodity servers.

Here is a quick recipe for starting a first Debian based Cassandra server in your Cassandra cluster.

 

Modify Debian repositories

 

  • Modify default apt sources and make sure you have Contrib in sources:
# vim /etc/apt/sources.list
deb http://http.debian.net/debian jessie main contrib non-free
deb-src http://http.debian.net/debian jessie main contrib non-free
deb http://http.debian.net/debian jessie-updates main contrib non-free
deb-src http://http.debian.net/debian jessie-updates main contrib non-free
deb http://security.debian.org/ jessie/updates main contrib non-free
deb-src http://security.debian.org/ jessie/updates main contrib non-free

 

  • Add Cassandra to sources:
# vim /etc/apt/sources.list.d/cassandra.list
deb http://www.apache.org/dist/cassandra/debian 37x main
deb-src http://www.apache.org/dist/cassandra/debian 37x main

 

Install Oracle Java JDK

Visit Oracle website and download Oracle JDK tar.gz package from Oracle website

http://www.oracle.com/technetwork/java/javase/downloads/index.html

 

 Install Java and Cassandra

sudo -i
apt-get update && apt-get install java-package && exit
apt install libgl1-mesa-glx libgtk2.0-0 libxxf86vm1 -y
make-jpkg jdk-8u51-linux-x64.tar.gz
dpkg -i oracle-java8-jdk_8u91_amd64.deb
update-alternatives --config java # and choose Oracle version
apt-get install cassandra -y

 

Is it running?

# systemctl status cassandra
cassandra.service - LSB: distributed storage system for structured data
Loaded: loaded (/etc/init.d/cassandra)
Active: active (running) since Wed 2016-06-22 13:23:54 UTC; 17min ago
CGroup: /system.slice/cassandra.service
└─17055 java -Xloggc:/var/log/cassandra/gc.log -ea -XX:+UseThreadPriorities -XX:ThreadPriorityPolicy=42 -XX:+Heap

Working with Cassandra

cqlsh
nodetool status
nodetool info
nodetool tpstats

Example output:

$ cqlsh

Connected to Test Cluster at 127.0.0.1:9042.
[cqlsh 5.0.1 | Cassandra 3.7 | CQL spec 3.4.2 | Native protocol v4]
Use HELP for help.
cqlsh> 

$ nodetool status

Datacenter: datacenter1
=======================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
--  Address    Load       Tokens       Owns (effective)  Host ID                               Rack
UN  127.0.0.1  105.98 KiB  256          100.0%            c1ad1f98-170a-4a29-a007-46fd1dda4506  rack1

Easy!

Mar 042016
 

Installing on Centos 6

I need PostgreSQL 9.3 on my Centos 6 box

yum localinstall https://download.postgresql.org/pub/repos/yum/9.3/redhat/rhel-6-x86_64/pgdg-centos93-9.3-2.noarch.rpm

yum list postgres*
yum install postgresql93-server
service postgresql-9.3 initdb

chkconfig postgresql-9.3 
service postgresql-9.3 start
service postgresql-9.3 status

 

Login to database

sudo -i -u postgres
psql --username=postgres -l 
# list all databases on psql prompt
\list or \l
# list all tables in the current database
\dt

 

Enabling password auth

sudo vi /var/lib/pgsql/data/pg_hba.conf

Find the lines that looks like this, near the bottom of the file:

# pg_hba.conf excerpt (original)
host    all             all             127.0.0.1/32            ident
host    all             all             ::1/128                 ident

Then replace “ident” with “md5”, so they look like this:

# pg_hba.conf excerpt (updated)
host    all             all             127.0.0.1/32            md5
host    all             all             ::1/128                 md5

Save and exit. PostgreSQL is now configured to allow password authentication.

Extensions

IF you need extensions, like RegExp-optimized index extension pg_trgm, you are going to need postgresql-contrib package. Once you have it installed, run:

$ sudo -u postgres sh
$ psql puppetdb -c 'create extension pg_trgm'
$ exit

 

File based backup

service postgresql stop
tar -czf /backup/full_postgres_backup-`date +%Y%m%d`.tar.gz' /var/lib/pgsql/data
service postgresql start

Single DB dump, for example spacewalk database

su - postgres -c 'pg_dump rhnschema |gzip -c > /backup/rhnschema_postgres_backup-`date +%Y%m%d`.sql.gz'

Backing up from cron

Moar scripts here https://github.com/zmielna/backup_scripts

# crontab -l
01 3 * * * /root/bin/postgresql_dump.sh 2>&1 |logger

vim /root/bin/postgresql_dump.sh

#!/bin/bash
#############################################################################
# Simple script to create a snapshot of a PostgreSQL databases.
# Can be run from cron like that
# 01 3 * * * /root/bin/postgresql_dump.sh 2>&1 |logger
# 
# Send bugreports, fixes, enhancements, t-shirts, money, beer & pizza to devnull@mielnet.pl
#############################################################################

#------------ variables
# Directory to store backups in
DST=/backup/dbback_postgresql
# DATABASES="postgres rhnschema"
DATABASES=`su - postgres -c "psql --username=postgres -l -x"|grep Name|grep -v template|cut -d"|" -f2|xargs`

# Any backups older than this will be deleted first
KEEPDAYS=7
DATE=$(date  +%Y-%m-%d)
#------------ code
/bin/logger "Starting PostgreSQL Dump....."
# cd $DST
find ${DST} -type f -mtime +${KEEPDAYS} -exec rm -f {} \;
rmdir $DST/* 2>/dev/null
mkdir -p ${DST}/${DATE}
chown postgres. ${DST}/${DATE}
for db in $DATABASES ; do
        echo -n "Backing up ${db}... " | logger
	su - postgres -c  "pg_dump ${db} |gzip -c > ${DST}/${DATE}/${db}-`date +%Y%m%d`.sql.gz"
        echo -n "Done with $db." | logger
done
/bin/logger "OK, all PostgreSQL dumps done in $DST"