Postgres database cloud Migration by using crontab job sheduler

First Note Down the server and database information for which server and which database do you want to schecdule backup(crontab) jobs. For example i’m taking following servers and databases for scheduling backup jobs.

SERVER IP        DATABASE
10.10.10.1          chennai
10.10.10.2          mumbai
10.10.10.3          Pune

========================================================================
DATABASE SIZE CHECKING: 

• Before Taking backup mandatory to checking database size and free disk space available or not (For backup location).
• pg_size_pretty function which converts the size in bytes to human understandable format without pg_size_pretty means size will be show bytes format.

1.postgres=# SELECT pg_size_pretty(pg_database_size('chennai'));
 pg_size_pretty
----------------
 186 GB 
(1 row)

2.postgres=# SELECT pg_size_pretty(pg_database_size('mumbai'));
 pg_size_pretty
----------------
 338 GB
(1 row)


3.postgres=# SELECT pg_size_pretty(pg_database_size('Pune'));
 pg_size_pretty
----------------
 194 GB
(1 row)

4.postgres=# SELECT pg_size_pretty(pg_database_size('delhi'));
 pg_size_pretty
----------------
 55 GB
(1 row)

========================================================================
We are using custom backup format(Fc) 90-93% will be reduced to original file size, it taking time for 4-9 hours, backup time depends on transaction, For Example if your database size 200GB also if transaction is less backup will be complete 3-5 hours if you use parallel your backup will be two time faster than normal (-j 2 two time faster than normal,-j 4 four time faster than normal) but parallel option only available from 9.3.

POSTGRESQL BACKUP SCRIPT FOR DIFFERENT SERVER DATABASES :

PREPARE THE CRONTAB.
list out the crontab jobs first before adding or editing jobs.
bash-4.1$ crontab -l

For Editing or adding the crontab Jobs.
bash-4.1$ crontab -e

Before  scheduling crontab job just check the server timing becouse your server timing and Desktop timing may be different.
bash-4.1$ date
Thu Oct 19 13:36:19 IST 2017  here 13 is 1 pm
—————————————
1.Backup of Chennai:

53 12 19 * * sh /home/postgres/eds/chennai.sh

----chennai.sh-------
export PATH=/opt/PostgreSQL/9.3/bin:$PATH
export PGDATA=/opt/PostgreSQL/9.3/data
export PGDATABASE=postgres
export PGUSER=postgres
export PGPORT=5432
export PGLOCALEDIR=/opt/PostgreSQL/9.3/share/locale
export MANPATH=$MANPATH:/opt/PostgreSQL/9.3/share/man
pg_dump -Fc chennai > /backup/chennai.dump

2.Backup of  Mumbai:

40 12 19 * * sh /home/postgres/edbscripts/mumbai.sh

-----mumbai.sh-----
export PATH=/opt/PostgreSQL/9.2/bin:$PATH
export PGDATA=/data
export PGDATABASE=postgres
export PGUSER=postgres
export PGPORT=5432
export PGLOCALEDIR=/opt/PostgreSQL/9.2/share/locale
export MANPATH=$MANPATH:/opt/PostgreSQL/9.2/share/man
pg_dump -Fc mumbai > /backup/mumbai.dump

3.Backup of  Pune:

40 13 19 * * sh /home/postgres/eds/pune.sh

----pune.sh----
export PATH=/opt/PostgreSQL/9.3/bin:$PATH
export PGDATA=/opt/PostgreSQL/9.3/data
export PGDATABASE=postgres
export PGUSER=postgres
export PGPORT=5432
export PGLOCALEDIR=/opt/PostgreSQL/9.3/share/locale
export MANPATH=$MANPATH:/opt/PostgreSQL/9.3/share/man
pg_dump -Fc Pune  -f /backup/pune.dump

4.Backup of delhi:

37 14 19 * * sh /home/postgres/edbscripts/delhi.sh

----delhi.sh----
export PATH=/opt/PostgreSQL/9.2/bin:$PATH
export PGDATA=/opt/PostgreSQL/9.2/data
export PGDATABASE=postgres
export PGUSER=postgres
export PGPORT=5432
export PGLOCALEDIR=/opt/PostgreSQL/9.2/share/locale
export MANPATH=$MANPATH:/opt/PostgreSQL/9.2/share/man
pg_dump -Fc delhi  -f /backup/delhi.dump

NOTE: After backup complete comments the crontab section otherwise this job will run every month of 19,2.37pm

========================================================================
Rename the database:

postgres=# ALTER DATABASE  delhi RENAME TO  delhi_old;
ALTER DATABASE

Also ensure that there are no other clients connected to the database at the time.
========================================================================
RESTORE THE DATABASE:

1.Restoring Chennai:

postgres=# ALTER DATABASE  chennai RENAME TO  chennai_old;
ALTER DATABASE
postgres=# create database chennai;
CREATE DATABASE

monitor the master and slave when restoring backup whether growing or not.
MASTER:

postgres=# SELECT pg_size_pretty(pg_database_size('chennai'));
 pg_size_pretty
----------------
 7233 kB
(1 row)

SLAVE:

postgres=# SELECT pg_size_pretty(pg_database_size('chennai'));
 pg_size_pretty
----------------
 7233 kB
(1 row)

Before setting the crontab just check the date
bash-4.2$ date
Sat Oct 21 08:24:39 IST 2017

AT CRONTAB:

crontab -e
53 12 21 * * sh /opt/PostgreSQL/9.6/cron_script/chennai_restore.sh

----chennai_restore.sh-------
export PATH=/opt/PostgreSQL/9.6/bin:$PATH
export PGDATA=/opt/PostgreSQL/9.6/data
export PGDATABASE=postgres
export PGUSER=postgres
export PGPORT=5432
export PGLOCALEDIR=/opt/PostgreSQL/9.6/share/locale
export MANPATH=$MANPATH:/opt/PostgreSQL/9.6/share/man


TODAY=$(date +"%m-%d-%Y-%T")
LOG=/opt/PostgreSQL/9.6/cron_script
echo "chennai restore start Time: `date +%d-%m-%y-%T`" >> $LOG/chennai_$TODAY.log
pg_restore -d mhrornas  /backup/chennai.dump
echo "chennai restore End Time: `date +%d-%m-%y-%T`" >> $LOG/chennai_$TODAY.log

2.Restoring  Mumbai:

postgres=# ALTER DATABASE  mumbai  RENAME TO  mumbai_old;
ALTER DATABASE
postgres=# create database mumbai;
CREATE DATABASE

monitor the master and slave when restoring backup whether growing or not.
MASTER:

postgres=# SELECT pg_size_pretty(pg_database_size('mumbai'));
 pg_size_pretty
----------------
 7233 kB
(1 row)

SLAVE:

postgres=# SELECT pg_size_pretty(pg_database_size('mumbai'));
 pg_size_pretty
----------------
 7233 kB
(1 row)

Before setting the crontab just check the date
bash-4.2$ date
Sat Oct 21 08:24:39 IST 2017

AT CRONTAB:

crontab -e
26 11 21 * * sh /opt/PostgreSQL/9.6/cron_script/mumbai_restore.sh

----mumbai_restore.sh----
export PATH=/opt/PostgreSQL/9.6/bin:$PATH
export PGDATA=/opt/PostgreSQL/9.6/data
export PGDATABASE=postgres
export PGUSER=postgres
export PGPORT=5432 
export PGLOCALEDIR=/opt/PostgreSQL/9.6/share/locale
export MANPATH=$MANPATH:/opt/PostgreSQL/9.6/share/man

pg_restore  -d mumbai  /backup/mumbai.dump

3.Restoring  Pune:
Rename the Existing database:

postgres=# ALTER DATABASE  Pune  RENAME TO  Pune_old;
ALTER DATABASE
postgres=# create database Pune;
CREATE DATABASE

monitor the master and slave when restoring backup whether growing or not.
MASTER:

postgres=# SELECT pg_size_pretty(pg_database_size('Pune'));
 pg_size_pretty
----------------
 7233 kB
(1 row)

SLAVE:
postgres=# SELECT pg_size_pretty(pg_database_size('Pune'));
 pg_size_pretty
----------------
 7233 kB
(1 row)

Before setting the crontab just check the date
bash-4.2$ date
Sat Oct 21 12:47:23 IST 2017

AT CRONTAB:

crontab -e
 50 12 21 * * sh /opt/PostgreSQL/9.6/cron_script/pune_restore.sh

----pune_restore.sh----
export PATH=/opt/PostgreSQL/9.6/bin:$PATH
export PGDATA=/opt/PostgreSQL/9.6/data
export PGDATABASE=postgres
export PGUSER=postgres
export PGPORT=5432
export PGLOCALEDIR=/opt/PostgreSQL/9.6/share/locale
export MANPATH=$MANPATH:/opt/PostgreSQL/9.6/share/man

pg_restore -d Pune   /backup/pune.dump

4.Restoring delhi:

postgres=# ALTER DATABASE  delhi RENAME TO  delhi_old;
ALTER DATABASE
postgres=# create database delhi;
CREATE DATABASE

AT CRONTAB:

crontab -e
 25 23 20 * * sh /opt/PostgreSQL/9.6/cron_script/delhi_restore.sh

----delhi_restore.sh----
export PATH=/opt/PostgreSQL/9.6/bin:$PATH
export PGDATA=/opt/PostgreSQL/9.6/data
export PGDATABASE=postgres
export PGUSER=postgres
export PGPORT=5432
export PGLOCALEDIR=/opt/PostgreSQL/9.6/share/locale
export MANPATH=$MANPATH:/opt/PostgreSQL/9.6/share/man

pg_restore  -d delhi   /backup/delhi.dump

========================================================================

• Restored database smaller than original
• By dumping and restoring the database, you are recreating a DB without all this free space. This is essentially what the VACUUM FULL command does – it rewrites the current data into a new file, then deletes the old file.
•  if you inserted 100 rows into a table, then deleted every row with an odd numbered ID, the DBMS could write out a new table with only 50 rows, but it’s more efficient for it to simply mark the deleted rows as free space and reuse them when you next insert a row. Therefore the table takes up twice as much space as is currently needed.

[root@MHSDC-SCDLR-MONTR backup]# scp delhi.dump root@10.187.200.20:/backups/                                                                                                                    
 root@10.187.200.15's password:
delhi.dump   
[root@MHSDC-SCDLR-DB5 backup]# scp mumbai.dump root@10.187.200.20:/backups/

changing Permission:

[root@DBServers1 backup]# chown postgres:postgres pune.dump