disk_usage.rb

This script will email foo@example.com when the disk space left on either sda1 and sda2 falls below 5GB. The threshold is just a variable you can change. You can also add to or remove from the list of sda devices you want to monitor using the disks array.

[cci lang="ruby"]
#!/usr/bin/env ruby

require ‘rubygems’
require ‘send_gmail’

TO_EMAIL = ‘foo@example.com’

filesys = `df -h`

disks = [1,2]

disks.each do |i|
r = filesys[/sda#{i}\s+[\d\.]+[MG]\s+[\d\.]+[MG]\s+([\d\.]+[MG])/,1]
message = “Low disk space on /sda#{i}: only #{r.to_i}GB remaining”
hsh={:to=>TO_EMAIL, :subject=>’Low disk space warning!’, :body=>message}
SendGMail.send_gmail(hsh) if r.to_i < 5 or r[/M$/]
puts message if r.to_i < 5 or r[/M$/]
end
[/cci]

load_check.rb

This script will use the uptime command to get the avarage load. I’m just using the 1min and 5min averages. If the 1min average load is over 9 or the 5min average load is over 4, bar@example.com will get an email.

[cci lang="ruby"]
#!/usr/bin/env ruby

require ‘rubygems’
require ‘send_gmail’

TO_EMAIL = ‘bar@example.com’

uptime = `uptime`

load_1min = uptime.split(” “)[8].chop()
load_5min = uptime.split(” “)[9].chop()

message = “Load on server is 1min/5min avg: #{load_1min} / #{load_5min} ”

hsh={:to=>TO_EMAIL, :subject=>’Load warning!’, :body=>message}
SendGMail.send_gmail(hsh) if (load_1min.to_i > 9) or (load_5min.to_i > 4)
[/cci]

You may have noticed an included module “send_gmail” and a call to “SendGMail” in the previous scripts. Since I use Gmail for all my outbound emails, the underlying alert system needs a way to make calls to the Gmail servers. Problem solved using this nifty little Ruby Gmailer script I found on at http://codingfrenzy.alexpmay.com/2007/12/sending-gmail-from-standalone-ruby.html.  I did make a few modifications to the script, so I’m including it here. You’ll want to set your gmail account/domain info if you do use this mailer.

send_gmail.rb

[cci lang="ruby"]
#!/usr/bin/env ruby

require ‘rubygems’

gem ‘actionmailer’
require ‘action_mailer’
require ‘openssl’
require ‘net/smtp’

module SendGMail

@user_name=’someone@example.com’
@domain=’example.com’
@password=’password’

def SendGMail.send_gmail(hsh)

raw_attachments=hsh.fetch(:raw_attachements, [])
if hsh.has_key?(:raw_attachment)
raw_attachments.push(hsh[:raw_attachment])
end

mail=TMail::Mail.new
mail.to=hsh[:to]
mail.date=Time.now
mail.from=@user_name
mail.subject=hsh[:subject]

main=mail
main=TMail::Mail.new
main.body = hsh[:body]
main.set_content_type(‘text/plain’, nil, ‘charset’=>’utf-8′)
mail.parts.push(main)

for raw_attachment in raw_attachments
part = TMail::Mail.new
transfer_encoding=raw_attachment[:transfer_encoding]
body=raw_attachment[:body]
case (transfer_encoding || “”).downcase
when “base64″ then
part.body = TMail::Base64.folding_encode(body)
when “quoted-printable”
part.body = [body].pack(“M*”)
else
part.body = body
end

part.transfer_encoding = transfer_encoding
part.set_content_type(raw_attachment[:mime_type], nil, ‘name’ => raw_attachment[:filename])
part.set_content_disposition(“attachment”, “filename”=>raw_attachment[:filename])
mail.parts.push(part)
end

mail.set_content_type(‘multipart’, ‘mixed’)
ActionMailer::Base.deliver(mail)

end

ActionMailer::Base.smtp_settings = {
:address => ‘smtp.gmail.com’,
:domain => @domain,
:authentication => :plain,
:port => 587,
:user_name => @user_name,
:password => @password
}

Net::SMTP.class_eval do
private
def do_start(helodomain, user, secret, authtype)
raise IOError, ‘SMTP session already started’ if @started
check_auth_args user, secret if user or secret

sock = timeout(@open_timeout) { TCPSocket.open(@address, @port) }
@socket = Net::InternetMessageIO.new(sock)
@socket.read_timeout = 60 #@read_timeout
@socket.debug_output = STDERR #@debug_output

check_response(critical { recv_response() })
do_helo(helodomain)

raise ‘openssl library not installed’ unless defined?(OpenSSL)
starttls
ssl = OpenSSL::SSL::SSLSocket.new(sock)
ssl.sync_close = true
ssl.connect
@socket = Net::InternetMessageIO.new(ssl)
@socket.read_timeout = 60 #@read_timeout
@socket.debug_output = STDERR #@debug_output
do_helo(helodomain)

authenticate user, secret, authtype if user
@started = true
ensure
unless @started
# authentication failed, cancel connection.
@socket.close if not @started and @socket and not @socket.closed?
@socket = nil
end
end

def do_helo(helodomain)
begin
if @esmtp
ehlo helodomain
else
helo helodomain
end
rescue Net::ProtocolError
if @esmtp
@esmtp = false
@error_occured = false
retry
end
raise
end
end

def starttls
getok(‘STARTTLS’)
end

def quit
begin
getok(‘QUIT’)
rescue EOFError, OpenSSL::SSL::SSLError
end
end
end
end

[/cci]

1. First fire up a new server on Slicehost (even though it’s not LTS, we’ll use Ubuntu 9.04). 
   After the server is provisioned, ssh in as root.  For simplicity, I’ve done this entire
   exercise as root.  Obviously on a production server, you’ll want to create the necessary
   non-root account.
   
   
2. Next let’s get our server up to date and necessary repos added. 
   If you are already root, you won’t need the ‘sudo’:
   
   
   
   
3. Add this line to the end of your ‘sources.list’ file:
   
   
   
   
4. Now run this series of commands from the shell. This will bring Ubuntu
   up to date with the latest patches, etc. Also it will install some useful
   shell tools like locate to help you quickly find files on the filesystem.
   
   
   
   
5. Now install the necessary Java packages and the Ant build tool:
   
   
   
   
6. After you have run through the install steps, you can test the success of the
   install by checking where java was installed and which version is recognized:
   
   
   
   
7. You can do this as a non-root account, but I built Red5 with Ant from the root account.
   After the build completes, copy the build output into /usr/share.
   
   
   
   
8. Now we can check if Red5 can be brought to life:
   
   
   
   
   We can check with netstat that Red5 is running on the default port of 5080:
   
   
   
   
   And to confirm, connect to port 5080 via telnet:
   
   
   
   
9. Go ahead and cancel out of telnet. Confirm that the Red5 start page is accessible via a browser by navigating to:
   
   http://[yourdomain]:5080/
   
   You should see this Red5 page:
   
   
   
   
10. At this point, you can watch the really nice YouTube video that the Red5 team has put together which is embedded on this Red5 start page. It will guide you thru the process of installing a couple of demo applications and then testing them… Remember when you are testing the demo apps to change the ip address of the server you are connecting to. If you are using a remote server, it won’t be ‘localhost’ but the ip address of the remote machine.