how to run EBS(create snapshot) by using cron

previously I have shown you how to integrate EBS and create snapshot of that volume where EBS is running.

sometime it is necessary to take the snapshot using cron. which is very much easy just save the following code into a file. and run the with the cron job and you are done. remember that in that case you have to installed EC2-api-tools on the Ec2 instance. and need to configure all environment variable. this codes i have found from Eric Hammond's blog.



#!/usr/bin/perl -w
#
# ec2-snapshot-xfs-mysql - EBS snapshot XFS file system with MySQL database
#
# Usage:
#
# ec2-snapshot-xfs-mysql XFSMOUNTPOINT VOLUMEID
#
# Requires:
#
# Amazon EC2 API tools should be installed on the instance,
# especially /usr/local/bin/ec2-create-snapshot
#
# MySQL username and password are stored in $HOME/.my.cnf in the
# usual manner following this format:
#
# [client]
# user=MYUSERNAME
# password=MYPASSWORD


use strict;
use DBI;

BEGIN {
$ENV{PATH} = '/bin:/usr/bin:/usr/local/bin';
}

my ($mountpoint, $volume_id) = @ARGV;
die "Usage: $0 XFSMOUNTPOINT VOLUMEID" unless $mountpoint && $volume_id;

# Get the MySQL username/password from $HOME/.my.cnf and connect
my ($username, $password);
open(FH, "$ENV{HOME}/.my.cnf") or die "Unable to open .my.cnf: $!";
while ( defined (my $line = ) ) {
$username = $1 if $line =~ m%^\s*user\s*=\s*(\S+)%;
$password = $1 if $line =~ m%^\s*password\s*=\s*(\S+)%;
}
close(FH);
my $dbh = DBI->connect('DBI:mysql:;host=localhost', $username, $password);

# Flush, lock, freeze
$dbh->do(q{ FLUSH TABLES WITH READ LOCK });
my ($logfile, $position) = $dbh->selectrow_array(q{ SHOW MASTER STATUS });
system('sudo', 'xfs_freeze', '-f', $mountpoint);

# Snapshot
my $snapshot_output = `ec2-create-snapshot $volume_id`;
my ($snapshot_id) = ($snapshot_output =~ m%(snap-[0-9a-f]{8})%);

# Thaw, unlock
system('sudo', 'xfs_freeze', '-u', $mountpoint);
$dbh->do(q{ UNLOCK TABLES });

print $snapshot_id ?
"$snapshot_id (master_log_file=\"$logfile\", master_log_pos=$position)\n"
:
"snapshot FAILED\n";


In my next post "problem you may find during running the corn of EBS" you will get issues you may find during running the corn job for EBS.

Cron job on ROR without any third party gem and library

When you are working of a large project it is very much natural that you will need to run cron job. suppose you want to take a back up of your database on every day. or you have such a site that you have to include a recurring billing system for the members. So what you will do now ?? simple you will need a cron job to do these sort of tasks. there are couple of ways you can run cron job on ROR. but all the cases you have to use third party gems or other things. here I will show you a simple way to run cronjob. without any third party gem or library and using the linux's crontab command.


you have to make a new class which actually extend the active records base class. for an instance suppose we are going to create an invoice_generator class which actually make an invoice on the first day of every month.

Here I am making the invoice_generator.rb file under app/cron folder. you can create it some where else.

class invoice_generator < ActiveRecord::Base

invoice = Invoice.new
company = Company.find_by_id(1)
invoice << company.generate_invoice
invoice.save!

end

Note: Here I am showing only the invoice_generator.rb file not all other files. these line of code will generate the invoice for only one company.

now you can test the file from the command line by running the following command

ruby script/runner app/cron/invoice_generator.rb

now you can run the same command from the linux's crontab command

$ crontab -e

then type

* * 1 * * ruby script/runner -e production /root/sami/test/app/cron/invoice_generator.rb

Note: here my aplication folder is test and that is under /root/sami directory