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Quick guide to Amazon EBS

2008-11-04T06:27:00Z

We've switched to use Amazon EBS(Elastic Block Storage) for a few months now. Therefore, we have been able to have a good night's sleep without worrying our database disappearing. Here's a quick guide.
It's very easy to use EBS for EC2. First make sure you downloaded the latest ec2-api-tools (you can't find EBS related tools in its old version). Here's my ec2-api-tools info (yours don't need to be exactly same with me):

12	$ ec2ver1.3-24159 2008-05-05

EC2 instance can only use EBS in the same avaliablity zone with it, so we need to check the availability zone in which your ec2 instances are. You can do this by

$ ec2din
...
INSTANCE i-abc12345 ami-abc12345 ec2-...compute-1.amazonaws.com ip-....ec2.internal running 0 m1.small 2008-06-23T23:12:26+0000 us-east-1b

So the instance is in us-east-1b. Now create a 200G storage block in this zone:

12	$ ec2-create-volume --size 200 -z  us-east-1bVOLUME vol-4d826724 200 creating 2008-10-14T00:00:00+0000

You can check the block by

12	$ ec2-describe-volumes vol-4d826724VOLUME vol-4d826724 200 available 2008-10-14T00:00:00+0000

The block now is created. It's like we have bought a 200G harddisk from amazon, now let's install it on our ec2 instance:

12	$ ec2-attach-volume vol-4d826724 -i i-6058a509 -d /dev/sdhATTACHMENT vol-4d826724 i-6058a509 /dev/sdh attaching 2008-10-14T00:15:00+0000

This will let the system on ec2 instance recognize our new block storage on /dev/sdh (you can specify any device name that not the same with currently used, like /dev/sdz). Now you can use this device (/dev/sdh) as a normal block device like other real disk partitions(such as /dev/sda). For example,

$ mkreiserfs /dev/sdh #this will format it with reiserfs
$ mkdir /mnt/data
$ mount /dev/sdh /mnt/data #mount the block to /mnt/data, now all data write to /mnt/data dir will be 
# persistent on the block storage vol-4d826724. it won't lost after you reboot the machine

Some other useful tools are:

ec2-describe-volumes: used to find the relationships between your blocks and instances
ec2-detach-volume: detach a block from instance

Here's a full manual of EBS.

Download youtube videos with ruby

2008-08-29T08:09:00Z

As you might know, we’ve released Ankoder.net for while now. It lets anyone to download videos into their iPods and various other formats. Scraping the flv url from Youtube HTML isnt exactly easy.

This is how we do it:

  def parse_youtube(url)
     youtube = "http://www.youtube.com/"
     # url =~ /(?:http\:\/\/.*youtube.com\/(?:watch\?v=|v\/))?(.*)$/
     url =~ /watch\?v=(.*)/ 
     video_id = $1
     video_id = video_id.split("&")[0]
     flv_url = nil
     open("#{youtube}watch\?v=#{video_id}") do |f|
       f.each_line do |line|
         if line =~ /watch_fullscreen\?(.*?)video_id=([\w-]+)&(.*?)&t=([\w-]+)&/
           # p line
           flv_url = "#{youtube}get_video?video_id=#{$2}&t=#{$4};auto"
           break
         end
       end
     end
     flv_url
  end

USER_AGENT = %{Mozilla/5.0 (Macintosh; U; Intel Mac OS X; en-US; rv:1.8.1.11) 
Gecko/20071231 Firefox/2.0.0.11 Flock/1.0.5}

IO.popen("curl -o \"#{file_name}\" -L -A \"#{USER_AGENT}\" \"#{parse_youtube(url)}\"  2>&1")

Uploading large files to Rails with Merb

2008-08-25T07:17:00Z

As you know Rails does bad on handling file upload, a large file will block your Rails app a long while, make it busy on receiving the file and can’t give response to other visitors, make them upset and leave you alone.

One solution is using merb to handle file upload for rails. The latest Merb that build on Rack(a cool framework who help you dealing with all kinds of http servers) does a really good job on uploading.

First, install merb:

sudo gem install merb

Second, create a merb app in your rails dir:

12	merb-gen app uploader cd uploader

You can ignore all other files except config/rack.rb, this is the only file we need to modify. Currently there’s only one line in the file:

    run Merb::Rack::Application.new

It will ask merb to handle the http request come from rack. Let us change this file to:

require 'cgi'

class File
  def to_s
    path
  end
end

# build a new handler to handler rack's request
  class Uploader 
    def call(env)
      # leverage merb's utility to parse the request.
      # Merb will save the file to a tempfile and save the tempfile's path in request's param
      request = Merb::Request.new(env)

      params = request.params

      # pass the params directly to the real (rails) app
      result = post("http://someplace.com/api", hash_to_params(params)).split("\n")[-1]
     
      # processing result or just ignore it ...
    end

    private

    def post(url, params="")
      curl_cmd = "curl -H \"Content-type: application/x-www-form-urlencoded\" #{url} -d \"#{params}\""
      puts "curl_cmd = #{curl_cmd}"
      f = IO.popen(curl_cmd +" 2>&1")
      result = f.read
      f.close
      result
    end

    def hash_to_params(hash)
      hash.map do |k, v|
        if v.kind_of? Hash
          h = {}
          v.each { |kk, vv| h["#{k}[#{kk}]"] = vv }
          hash_to_params h
        else
          "#{k}=#{CGI.escape v.to_s}"
        end
      end.join("&")
    end

  end

run Uploader.new

Run merb by

merb -p 1234 -c 1 -e production -d

Remember to config your apache or your favorite webserver to redirect all request from /uploader to port 1234 (Your merb uploader is listening here!).

Pretty easy, isn’t it?

The Facebook autocomplete address to: field.

2008-08-13T08:33:00Z

We've extended the Autocomplete.Local from Scriptaculous to implement the autocomplete to: field mimicing the Facebook's features. This was a little challenging at the start, but prototype.js and scriptaculous have just made it so much easier.

Concepts

json - array of contacts with names and email address and any other fields you wish to search
The input box changes size dynamically and reposition itself according to the keystrokes
Each 'token' created is an input field, submitting the id of the user or an email address

Straight to the source

Syntax

new Autocompleter.LocalAdvanced(id_of_text_field, id_of_div_to_populate, json_array, options)

The constructor takes four parameters. The first two are, as usual, the id of the monitored textbox, and id of the autocompletion menu. The third is an array of strings that you want to autocomplete from, and the fourth is the options block.

Extra local autocompletion options

Option	Default Value	Description
`search_field`	"name"	Which attribute to search in the json array.
`choices`	10	How many autocompletion choices to offer
`partialSearch`	off	If false, the autocompleter will match entered text only at the beginning of strings in the autocomplete array. Defaults to true, which will match text at the beginning of any word in the strings in the autocomplete array. If you want to search anywhere in the string, additionally set the option fullSearch to true
`fullSearch`	false	Search anywhere in autocomplete array strings.
`partialChars`	2	How many characters to enter before triggering a partial match (unlike minChars, which defines how many characters are required to do any match at all).
`ignoreCase`	true	Whether to ignore case when autocompleting

Example

HTML

 <div tabindex="-1" id="ids" class="clearfix tokenizer" onclick="$('autocomplete_input').focus()">
<span class="tokenizer_stretcher">^_^</span><span class="tab_stop"><input type="text" id="hidden_input" tabindex="-1"></span>
 <div id="autocomplete_display" class="tokenizer_input"> 
 <input type="text" size="1" tabindex="" id="autocomplete_input"   />
 </div>                                                                          
 </div>

<div id="autocomplete_populate" class="clearfix autocomplete typeahead_list" style="width: 358px; height: auto; overflow-y: hidden;display:none">
 <div class="typeahead_message">Type the name of a friend, friend list, or email address</div>                       
 </div>

Javascript

               (new Image()).src='/inbox/images/token.gif';
                        (new Image()).src='/inbox/images/token_selected.gif';
                        (new Image()).src='/inbox/images/token_hover.gif';
                        (new Image()).src='/inbox/images/token_x.gif';

                        var contacts = [
                        {name:"phoenix zhuang",email:"phoenix@rorcraft.com"}, 
                        {name:"jian xie",email:"jan.xie@rorcraft.com"}, 
                        {name:"isaiah peng",email:"isaiah.peng@rorcraft.com"}, 
                        {name:"chris chan",email:"chris.chan@rorcraft.com"}, 
                        {name:"rex chung",email:"rex@rorcraft.com"},
                        {name:"chung rex",email:"chung@rorcraft.com"},
                        {name:"chan chris",email:"chan@rorcraft.com"},
                        {name:"peng isaiah",email:"peng@rorcraft.com"} ];


                        var typeahead = new Autocompleter.LocalAdvanced('autocomplete_input', 'autocomplete_populate', contacts, {                                                  
                            frequency: 0.1,
                            updateElement: addContactToList,
                            search_field: "name"
                        });
                        var hidden_input = new HiddenInput('hidden_input',typeahead);

CSS

/* autcompleter.advancedlocal css */
.tokenizer{min-height:5px;padding:0px 0px 3px 3px;width:100%;background:#fff;font-size:11px;}
.tokenizer_locked{background:#f4f4f4;}
.tokenizer,
.tokenizer *{cursor:text}
.tokenizer input{width:100%;}
.tokenizer .tokenizer_input,
.tokenizer .token{float:left;margin-right:3px;margin-top:3px;}
.tokenizer .tab_stop,
.tokenizer .tokenizer_stretcher{display:block;float:left;overflow:hidden;width:0px;}
.tokenizer .tab_stop{height:0px;}
.tokenizer .tokenizer_stretcher{padding-top:7px;}
#autocomplete_input{width:20px;}
#facebook .tokenizer .tab_stop input{border:0px solid black;display:inline;position:relative;left:-500px;}
#facebook .tokenizer .tokenizer_input_borderless {left:4px;margin-left:-1px;overflow:hidden;position:relative;}
#facebook .tokenizer_input_borderless  #autocomplete_input{border:3px solid white!important;border-left:none;display:block;margin:-3px 3px -4px -2px;padding:0px!important;}
/*IE6-/Win only*/
/*\*/ * html#facebook .tokenizer_input_borderless #autocomplete_input { border:3px solid black;margin: -3px 3px -4px 14px:padding-left:10px; } /**/
.tokenizer div:-moz-first-node{padding-top:1px!important;}
.tokenizer_input{max-width:450px;overflow:hidden;padding:1px 0px;}
#facebook .tokenizer_input input,
.tokenizer_input_shadow{border:0px solid black;outline:0;font-family:'lucida grande', tahoma, verdana, arial, sans-serif;font-size:11px;padding:0px 5px;margin:0 0 -1px 0;white-space:pre;}
.tokenizer_input_shadow{display:inline;left:-10000px;position:absolute;top:-10000px;}
.tokenizer .tokenizer_input_shadow{height:0px;display:block;left:0px;overflow:hidden;position:relative;top:0px;}
div.tokenizer .token{background-image:url('/inbox/images/token.gif');background-repeat:no-repeat;color:black;white-space:nowrap;}
div.tokenizer .token span{background-image:url('/inbox/images/token.gif');background-position:top right;background-repeat:no-repeat;display:block;}
div.tokenizer .token span span{background-position:bottom right;}
div.tokenizer .token span span span{background-position:bottom left;}
div.tokenizer .token span span span span{background-image:none;padding:2px 3px 2px 5px;}
div.tokenizer.tokenizer_locked .token span span span span{padding-right:5px;}
html div.tokenizer_locked .token:hover,
html div.tokenizer_locked .token:hover span{background-image:url('/inbox/images/token.gif');}
div.tokenizer .token:hover,
div.tokenizer .token:hover span{background-image:url('/inbox/images/token_hover.gif');text-decoration:none;}
div.tokenizer .token_selected,
div.tokenizer .token_selected span,
div.tokenizer .token_selected:hover,
div.tokenizer .token_selected:hover span{background-image:url('/inbox/images/token_selected.gif');color:white;text-decoration:none;}
div.tokenizer .token span.x,
div.tokenizer .token span.x_hover,
div.tokenizer .token:hover span.x,
div.tokenizer .token:hover span.x_hover{background-image:url('/inbox/images/token_x.gif');background-position:4px 2px;cursor:pointer;display:inline;padding:0px 6px 0px 5px;}
div.tokenizer.tokenizer_locked .token span.x,
div.tokenizer.tokenizer_locked .token span.x_hover{display:none;}
div.autocomplete {  position:absolute;  width:355px;  background-color:white;  border:1px solid #888;  margin-top:-2px;  padding:0px;}
div.autocomplete ul {  list-style-type:none;margin:0px; padding:0px;}
div.autocomplete ul li.selected { background-color: #ffb;}
div.autocomplete ul li {  list-style-type:none;  display:block;  margin:0;  padding:2px;  height:32px;cursor:pointer;}
/* end of autcompleter.advancedlocal css */

Download the full source

Autocomplete_AdvancedLocal.zip

[update] We've forked a version of the control.js and changed all reference to element.style to setStyle(). It was causing script errors in IE.
http://github.com/rorcraft/scriptaculous/tree/master/src/controls.js

Patching paperclip to create thumbnails only for images

2008-08-01T09:25:00Z

Paperclip has some good features over attachment_fu that "attached files don’t need to have a seperare model (thank god). Your attachments are treated just like any other atribute. Images aren’t saved until your model is saved" ( by Jim Neath ).

The fall back of paperclip is that it tries to create a thumbnail for any type of file, including pdf. It won't cause much problem if it cannot create a thumbnail to a certain file. But when it comes to pdf file, paperclip tries to generate a thumbnail for every page of the file, it becomes very slow when uploading the pdf file if the file has hundreds of pages. Sometimes it even times out! At the same time, attachment_fu does not have this problem.

attachment_fu.rb includes a class method #images? to distinguish if the file is an image.

1234	129 # Returns true or false if the given content type is recognized as an image.130 def image?(content_type)131 content_types.include?(content_type)132 end

Content types of images are initialized at the begin of the file:

5  @@content_types = ['image/jpeg', 'image/pjpeg', 'image/gif', 'image/png', 'image/x-png', 'image/jpg']

Then the #image? method is called in a instantial method #thumbnailable:

216       # Checks whether the attachment's content type is an image content type
217       def image?
218         self.class.image?(content_type)
219       end
220
221       # Returns true/false if an attachment is thumbnailable.  
            # A thumbnailable attachment has an image content type and the parent_id attribute.
222       def thumbnailable?
223         image? && respond_to?(:parent_id) && parent_id.nil?
224       end

In the #create_or_update_thumbnail it test if the content is thumbnailable? to determine going or not.

243   # Creates or updates the thumbnail for the current attachment.
244       def create_or_update_thumbnail(temp_file, file_name_suffix, *size)
245         thumbnailable? || raise(ThumbnailError.new("Can't create a thumbnail if the content \
 type is not an image or there is no parent_id column"))
246         returning find_or_initialize_thumbnail(file_name_suffix) do |thumb|
247           thumb.attributes = {
248             :content_type             => content_type,
249             :filename                 => thumbnail_name_for(file_name_suffix),
250             :temp_path                => temp_file,
251             :thumbnail_resize_options => size
252           }
253           callback_with_args :before_thumbnail_saved, thumb
254           thumb.save!
255         end
256       end

Paperclip has a similar structure like this, it makes it easier to make this patch.

From line #217
    def post_process #:nodoc:
      return if @queued_for_write[:original].nil?
      logger.info("[paperclip] Post-processing #{name}")
      @styles.each do |name, args|
        begin
          dimensions, format = args
          dimensions = dimensions.call(instance) if dimensions.respond_to? :call
          @queued_for_write[name] = Thumbnail.make(@queued_for_write[:original],
                                                   dimensions,
                                                   format,
                                                   @whiny_thumnails)
        rescue PaperclipError => e
          @errors << e.message if @whiny_thumbnails
        end
      end
    end

The trick here is to add the #thumbnailable? method in right after the #begin keyword and raise a PaperclipError if it fails:

213     def post_process #:nodoc:
214       return if @queued_for_write[:original].nil?
215       @styles.each do |name, args|
216         begin
                # Test here
217           thumbnailable? || raise(PaperclipError.new("Can not create thumbnails \
 if the content type is not an image."))
218           dimensions, format = args
219           dimensions = dimensions.call(instance) if dimensions.respond_to? :call
220           @queued_for_write[name] = Thumbnail.make(@queued_for_write[:original],-
221                                                    dimensions,
222                                                    format,-
223                                                    @whiny_thumnails)
224         rescue PaperclipError => e
225           @errors << e.message if @whiny_thumbnails
226         end
227       end
228     end

Add the #image? and #thumbnailable? method to attachment.rb of paperclip, and initialize the thumbnailable content types at the beginning. That's all, now you can upload pdf files very fast.

About how to use paperclip, Jim Neath has a great tutorial Paperclip: Attaching Files in Rails. Enjoy it!

Amazon EC2 finally support static IP addresses

2008-04-02T09:25:00Z

To enable the static IP addresses function , you need to download the latest Amazon EC2 Command-Line Tools, the download link of it is http://developer.amazonwebservices.com/connect/entry.jspa?externalID=351&categoryID=88

after download, I recommend to unzip it to a folder call ec2 under your home path

123	mkdir ~/ec2cd ~/ec2unzip ec2-api-tools.zip

you can now see a folder call ec2-api-tools-1.3-19403 under the ec2 folder.

now it is time to update the .profile , so that EC2 tool can find the library that it use.

you have to download the private and public cert from amazon

nano ~/.profile
export PATH=~/ec2/ec2-api-tools-1.3-19403/bin:$PATH
export EC2_HOME=~/ec2/ec2-api-tools-1.3-19403
export EC2_CERT=~/.ec2/cert-xxxxxxxxx.pem
export EC2_PRIVATE_KEY=~/.ec2/pk-yyyyyy.pem

then you can start a new console so that the profile update will be effective.

you can now allocate a new IP address for your account.

12	Chris:~ chrischan$ ec2-allocate-address ADDRESS 75.101.139.212

This new IP 75.101.140.212 is not bundle to any AMI instance yet.
You have to manually assign this IP address to a instance

First, you need to know the instance that you have already started. you can use the following command

Chris:~ chrischan$ ec2-describe-instances 
  RESERVATION     r-3c1bea55      073126868754    default
INSTANCE        i-7124dd30      ami-5035d079    ec2-67-202-34-115.compute-1.amazonaws.com      
domU-12-31-38-00-6D-98.compute-1.internal       running         0m1.small 2008-03-05T15:51:36+0000 
us-east-1a

you can see that the instance id is i-7124dd30, we can then assign the IP to that instance

12	Chris:~ chrischan$ ec2-associate-address 75.101.140.212 -i i-7124dd30ADDRESS 75.101.140.212 i-7124dd30

If you want to check the address allocation status, you can use the follow command

12	Chris:~ chrischan$ ec2-describe-addresses ADDRESS 75.101.140.212 i-7124dd30

for any time if you want to free the IP , you can use

ec2-release-address IP-address

If you want to assign the existing IP address to a new instance , you can use ec2-associate-address, but this time , you assign the new instance IP, and the existing IP address bundling will remove, so the single IP address will always only bundle to one instance.

Also, a instance can only have one IP address assocate to it , so when you assign a new IP address to a instance, all the existing IP bundling will be removed. And all the IP address in this status will start to charge you account. So whenever any IP allocate has finished , please make to use ec2-describe-addresses to check the IP address bundling status.

Ankoder Architecture presentation

2008-03-26T09:16:00Z

In March, we had a ruby on rails user group meetup in Hangzhou, China. It was exciting to meet more rails developers in China and shares some experience on our projects. Hangzhou is famous for it’s West Lake, it is just 1.5 hrs south of Shanghai. It is turning into the Silicon Valley of China, because several large internet companies are based in Hangzhou, such as Alibaba. They are also experimenting with Rails, because of its amazing productivity gains.

We did a presentation on our architecture and how we host a fault tolerant system on Amazon’s EC2. We will already need to change this a little since Amazon has just released the long been waited feature Static IP. Now you don’t need to rely on DNS to failover to your new server, you can at least start a new instance and point your IP to the new host.

| View | Upload your own

Ankoder API ruby library released

2008-02-25T10:45:00Z

Do you need to build a mini youtube for your client?

Do you want to include video functionalities to your site?

We’ve released the ruby library that we are already using on http://free.ankoder.com both in rails plugin form as well as ruby gem form.

Install it and have a look at the rdoc

Rails Plugin

http://ankoder.googlecode.com

script/plugin install http://ankoder.googlecode.com/svn/trunk/trunk/ankoder_on_rails

Ruby Gem

http://rubyforge.org/projects/ankoder/

$ sudo gem install ankoder
Password:
Bulk updating Gem source index for: http://gems.rubyforge.org
Successfully installed ankoder-0.0.2-
Installing ri documentation for ankoder-0.0.2-...
Installing RDoc documentation for ankoder-0.0.2-...

Send us an email if you’re keen to try it.

We’re working on our payment model and cleaning up the UI so you can manage your services.

mpeg4aac for ffmpeg problem

2008-01-15T02:01:00Z

Error Message:

library: cannot resolve faacDecGetErrorMessage in libfaad.so.0!

Solution:

First you should comfirm that libfaad.so.0 library is located in the path which are defined by the LD_LIBRARY_PATH environment variable. Otherwise, you can use


export LD_LIBRARY_PATH=/home/ffmpeg/usr/local/lib

to add the libfaad.so.0 to the LD_LIBRARY_PATH. (in this case, libfaad.so.0 is in the /home/ffmpeg/usr/local/lib ).

Second, Modify libavcodec/libfaad.c in ffmpeg source code


change line:
do { static const char* n = "faacDec" #a; \
To:
do { static const char* n = "NeAACDec" #a; \

change line:
#define dfaac(a, b)     s->faacDec ## a = faacDec ## a
To:
#define dfaac(a, b)     s->faacDec ## a = NeAACDec ## a

Re-compile ffmpeg.

Step by step guide to preparing EC2 on MacOSX

2008-01-08T02:51:00Z

Amazon provides two types of tool.

1. Operational tools that use to startup and shutdown AMI instances

2. Packaging tool to pack the AMI that created , or modify on existing public AMI and rebundle to new private AMI

Operational tool

Create a new AWS Access Identifiers if you don't already have.

$ mkdir ~/.ec2

download both the Private Key file and X.509 Certificate file to ~/.ec2

rename the pk-xxxxxxxxxx.pem one to PrivateKey.pem
rename the cert-xxxxxxxxx.pem one to 509certificate.pem
( xxxxxxxxxx stand for the random name generate by amazon )

visit the following to download the packaged file to Download folder

http://developer.amazonwebservices.com/connect/entry.jspa?externalID=351&categoryID=88

$ mkdir ~/ec2

$ cp ~/Downloads/ec2-api-tools.zip ~/ec2/

$ cd ~/ec2/

$ unzip ec2-api-tools.zip

$ nano ~/.profile

append the follow line to the end

export JAVA_HOME=/Library/Java/Home
export PATH=~/ec2/ec2-api-tools-1.2-13740/bin:$PATH
export EC2_HOME=~/ec2/ec2-api-tools-1.2-13740
export EC2_PRIVATE_KEY=~/.ec2/PrivateKey.pem
export EC2_CERT=~/.ec2/509certificate.pem

restart the terminal to active the changes on bash profile

$ ec2-describe-images -o amazon IMAGE ami-20b65349 ec2-public-images/fedora-core4-base.manifest.xml amazon available public
IMAGE ami-22b6534b ec2-public-images/fedora-core4-mysql.manifest.xml amazon available public
IMAGE ami-23b6534a ec2-public-images/fedora-core4-apache.manifest.xml amazon available public
IMAGE ami-25b6534c ec2-public-images/fedora-core4-apache-mysql.manifest.xml amazon available public
IMAGE ami-26b6534f ec2-public-images/developer-image.manifest.xml amazon available public
IMAGE ami-2bb65342 ec2-public-images/getting-started.manifest.xml amazon available public
IMAGE ami-36ff1a5f ec2-public-images/fedora-core6-base-x86_64.manifest.xml amazon available public
IMAGE ami-bd9d78d4 ec2-public-images/demo-paid-AMI.manifest.xml amazon available public A79EC0DB

If install sucessfully , will show the list of the AMI that amazon provide

$ ec2-add-keypair demo-keypair KEYPAIR ankoder d9:d9:85:95:5f:ef:19:c9:33:5b:78:e6:e7:82:cc:e2:6a:9f:70:76
-----BEGIN RSA PRIVATE KEY-----
MIIEowIBAAKCAQEAyfG40k8HRgFaZZqDUQu5FZAjyKFDOKgMLb0DpmP10oM3RCz4KBqHQfJgyjqs
5cz++qG1NDQ1HYVs7Ke45OshRU+ibIvRh57L1EcRetEerpXNZJ3qKkcj+wMvyAhEYo515DKCQbWG
+M8SVNDTdXDIFAZBxs2Bo9wvrbRn8J+cCyqRSkYl+CpfIen8LcU0TD6ssCASIaUW++z+Sj0iH9p/
+PirmSWhbEbFqgYNqUPrIuNitSYE1wEsPF+ckHuL18Vn7Zc4gMM9eOQ4+u+NgGpPMAs8ZY8Fu7tJ
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/4cFSHaDKnb5plNB3+DwPjjtDx/37PC6XAVTOPxaANr/lEkkST0vub+MkkQ/RxShLxKg
-----END RSA PRIVATE KEY-----

copy the above text including -----BEGIN RSA PRIVATE KEY----- and -----END RSA PRIVATE KEY----- to ~/.ssh/id_rsa-demo-keypair

$ nano ~/.ssh/id_rsa-demo-keypair

paste all the content to it and save

$ ec2-run-instances ami-25b6534c -k demo-keypair

RESERVATION r-b7fc17de 119012238391 default
INSTANCE i-6ea05007 ami-25b6534c pending ankoder 0 m1.small
2008-01-07T05:49:15+0000

if the terminal return the message similar to this , you have successfully started a AMI instance.

To show all the instances currently running can use the ec2-describe-instances command

$ ec2-describe-instances
INSTANCE i-6ea05007 ami-25b6534c ec2-67-202-24-116.compute-1.amazonaws.com
domU-12-31-38-00-29-48.compute-1.internal running ankoder m1.small
2008-01-07T05:49:15+0000

To shutdown a running instance, can first find the instance id by using `ec2-describe-instances` , the one that in format of i-xxxxxxxx is the instance id

$ ec2-terminate-instances i-6ea05007
INSTANCE i-6ea05007 running shutting-down

Allow the instance to be accessable from outside

$ ec2-authorize default -p 22
PERMISSION default ALLOWS tcp 22 22 FROM CIDR 0.0.0.0/0

$ ec2-authorize default -p 80
PERMISSION default ALLOWS tcp 80 80 FROM CIDR 0.0.0.0/0

$ ec2-authorize default -p 21
PERMISSION default ALLOWS tcp 80 21 FROM CIDR 0.0.0.0/0

To connect to the AMI instance from SSH
first check the hostname

$ ec2-describe-instances
INSTANCE i-55a0503c ami-25b6534c ec2-67-202-2-199.compute-1.amazonaws.com
domU-12-31-38-00-42-55.compute-1.internal running ankoder m1.small
2008-01-07T06:02:38+0000

using the private key that you generated to login
$ ssh root@ec2-67-202-2-199.compute-1.amazonaws.com -i ~/.ssh/id_rsa-demo-keypair

you can do whatever you like in this instance

install ec2onrails support tool
$ sudo gem install ec2onrails

As the Amazon EC2 tool is in rpm format, and MacOSX doesn't come with it.
so we have to use DarwinPorts to install rpm first

Install the rpm

$ sudo port install rpm

Install Amazon packaging tool

$ wget http://s3.amazonaws.com/ec2-downloads/ec2-ami-tools.noarch.rpm

$ sudo rpm -i ec2-ami-tools.noarch.rpm --nodeps --ignoreos

Also, there is a gem for access the EC2 from ruby

$ sudo gem install amazon-ec2 --include-dependencies

Generate PDFs in Rails with RFPDF

2007-12-19T23:30:00Z

1, Install railsrfpdf plugin ruby script/plugin install http://cnruby.googlecode.com/svn/trunk/rails-projects/infoq_rfpdf/vendor/plugins/railsrfpdf/

2, add new Mime type to environment.rb： Mime::Type.register “application/pdf”, :pdf

3, in the controller：

respond_to do |format| 
  format.html # show.rhtml 
  format.xml  { render :xml =&gt; @page.to_xml } 
  format.pdf do 
    pdf = FPDF.new 
    pdf.AddPage 
    pdf.SetFont("Arial",'B',18) 
    pdf.Cell(100, 20, "Hello World") 
    send_data pdf.Output, :filename =&gt; "hello.pdf", :type =&gt; "application/pdf" 
  end 
end

Useful method in RPDF SetFont(string family [, string style [, float size]]) SetMargins(float left, float top [, float right]) SetTextColor(int r [, int g, int b]) SetXY(float x, float y) AddFont(string family [, string style [, string file]]) Cell(float w [, float h [, string txt [, mixed border [, int ln [, string align [, int fill [, mixed link]]]]]]]) Image(string file, float x, float y [, float w [, float h [, string type [, mixed link]]]]) Line(float x1, float y1, float x2, float y2) MultiCell(float w, float h, string txt [, mixed border [, string align [, int fill]]]) Rect(float x, float y, float w, float h [, string style])

A case in real world

    pdf = FPDF.new('portrait', 'pt', [800, 1380]) 
    pdf.SetAutoPageBreak(false) 
    pdf.AddPage 
    # draw a rectangle 
    pdf.SetFillColor(240, 240, 240) 
    pdf.Rect(0, 0, 800, 895, 'F')    pdf.Image("#{RAILS_ROOT}/public/images/a.jpg", 0, 0, 800, 600) 
    # add four images 
    pdf.Image("#{RAILS_ROOT}/public/images/b.jpg", 0, 700, 260) 
    pdf.Image("#{RAILS_ROOT}/public/images/c.jpg", 270, 700, 260) 
    pdf.Image("#{RAILS_ROOT}/public/images/d.jpg", 540, 700, 260) 
    # write text 
    txt = 'Agile Web Development' 
    pdf.SetFont("Arial", 'B', 38) 
    pdf.SetXY(0, 600) 
    pdf.Cell(800, 100, txt, 10, 1, 'C') 
    pdf.SetTextColor(10, 10, 10) 
    txt = 'What is Ruby FPDF?' 
    pdf.SetFont("Arial", 'B', 30) 
    pdf.SetXY(20, 920) 
    pdf.Cell(300, 30, txt, 10, 1) 
    txt = "Ruby FPDF is a Ruby port of Olivier Plathey's excellent PDF generator, /
 FPDF. FPDF is written in PHP, 
and as such can only be used From PHP scripts. /
Ruby FPDF, as the name suggests, is written in Ruby and /
can be used From Ruby scripts.    Ruby FPDF was ported and is maintained by Brian Ollenberger. /
 If you need to contact me, see the contact link abovenYou can download Ruby FPDF below. /
 It is released under a permissive license, similar to that of FPDF. I only ask that you retain the /
 copyright notice at the top of the source file. You may make modifications to FPDF, but if you /
redistribute those modifications, make it clear in a comment immediately before or after the /
 copyright notice that you have modified it. I also wouldn't mind if you sent patches back to me, /
 but you are not strictly required to do so." 
    pdf.SetFont("Arial", '', 18) 
    pdf.SetXY(20, 960) 
    pdf.MultiCell(500, 20, txt) 
    txt = 'Ruby | On | Rails' 
    pdf.SetFont("Arial", '', 24) 
    pdf.SetXY(540, 920) 
    pdf.Cell(260, 30, txt, 10, 1, 'C') 
    #draw rectangle 
    pdf.SetFillColor(240, 240, 240) 
    pdf.Rect(550, 960, 230, 300, 'F') 
    #write text 
    txt = "* Get Excitednn* Get Startedn* Get BetternnContactnnEnjoy Railsnenjoyrails@gmail.com" 
    pdf.SetFont("Arial", 'B', 18) 
    pdf.SetXY(560, 970) 
    pdf.MultiCell(220, 36, txt) 
    pdf.SetFillColor(170, 0, 1) 
    pdf.Rect(0, 1310, 800, 70, 'F') 
    txt = 'View this page at http://devblog.rorcraft.com/' 
    pdf.SetTextColor(255, 255, 255) 
    pdf.SetFont("Arial", '', 28) 
    pdf.SetXY(0, 1330) 
    pdf.Cell(800, 24, txt, 0, 0, 'C') 
    send_data pdf.Output, :filename =&gt; "hello_advance.pdf", :type =&gt; "application/pdf"

Reference： 1: fpdf manual

2: How to Generate PDFs

3: PDF::Writer VS Ruby FPDF

4: Iconv Rdoc

5: fpdf website

Validating datetime - MultiparameterAssignmentErrors

2007-12-05T06:12:00Z

If you use the date_select, datetime_select helepers you’ll most likely see this error when the user submit an invalid date e.g. (Feb 30). Rails will raise MultiparameterAssignmentErrors.

The easiest way to fix this is by using this plugin for validates_datetime http://agilewebdevelopment.com/plugins/validates_date_time

However I just found that it has a bug with datetime_select, where it parse the (day, hour, minute) into (hour, minute, seconds).

Here is why: on line 179 of validates_date_time.rb in the lib/ folder of the plugin.

    def extract_time_from_multiparameter_attributes(values)
        values.last( 3 ).map { |s| s.rjust(2, "0") }.join(":")
    end
    
    # change it to this, it'll fix the problem.
    def extract_time_from_multiparameter_attributes(values)
        values.last( values.size > 5 ? 3 : 2 ).map { |s| s.rjust(2, "0") }.join(":")
    end

Optimising your search results with ferret

2007-11-20T08:20:00Z

Acts_as_ferret is a great plugin for adding search capability to your active records. If you use the default setup, you might find that ferret does not return some expected results. For example, if you have an article:

article: 
  id: 1
  title: this is an article

class Article < ActiveRecord
  
  acts_as_ferret( {:fields => {
    :name => {:boost => 3 },
    :published_at_for_sort => {:index => :untokenized_omit_norms, :term_vector => :no} 
  }, :remote => AAF_REMOTE} )

end

Article.find_by_contents(“article”)

return 1 result

Article.find_by_contents(“this is the article title”)

return 0 result

How to solve this?

Omit Stopword

The default analyser will remove common stop-words like “and”, “the”, “a” and “for”. You can create a new StandardAnalyzer that doesn’t remove those stopwords.

class Article < ActiveRecord
  
  acts_as_ferret( {:fields => {
    :name => {:boost => 3 },
    :published_at_for_sort => {:index => :untokenized_omit_norms, :term_vector => :no} 
  }, :remote => AAF_REMOTE} ,  {:analyzer => Ferret::Analysis::StandardAnalyzer.new([nil]) } )

end

PerFieldAnalyzer

Using the way above will include all the stopwords in every field, that is usually not what you want. What you need is to use PerFieldAnalyzer and only omit stopwords for title.

From the mailing list archive, there’s reported problem with the C version of PerFieldAnalayser. “Thanks to Ben from omdb.org for tracking this down and creating this workaround. You can read more about the issue there: blog.omdb-beta.org/2007/7/29/tracking-down-a-memory-leak-in-ferret-0-11-4”

Save this file as per_field_analaysis.rb in /lib

http://pastie.caboo.se/83194

class Article < ActiveRecord
  
  pfa = PerFieldAnalyzer.new( Ferret::Analysis::StandardAnalyzer.new )
  pfa[:name] = Ferret::Analysis::StandardAnalyzer.new([])

  acts_as_ferret( {:fields => {
    :name => {:boost => 3 },
    :published_at_for_sort => {:index => :untokenized_omit_norms, :term_vector => :no} 
  }, :remote => AAF_REMOTE} ,  {:analyzer => pfa } )

end

Nagios 4: notify by twitter

2007-11-05T09:53:00Z

Install Net::Twitter (perl version)

download from search.cpan.org

http://search.cpan.org/~cthom/Net-Twitter/

tar zxvf Net-Twitter-1.06.tar.gz
cd Net-Twitter-1.06
perl Makefile.PL
make
make test
sudo make install

Install other perl package if required（HTML-Tagset, libwww-perl, JSON-Any）

download them from http://search.cpan.org/

The script for twitter notify( change the user_name and password for twitter )

vi /usr/local/nagios/libexec/twitter.pl

#!/usr/bin/perl -w

use strict;
use Net::Twitter;
my $msg = shift;
my $twit = new Net::Twitter(username => "yourname",password => "yourpass");
if (defined($msg) && $msg !~ /^\s*$/) {
  $twit->update($msg);
}

sudo chown nagios:nagios twitter.pl

sudo chmod +x twitter.pl

send the test message to twitter

/usr/local/nagios/libexec/twitter.pl ‘hello world’

Add new command for notify in nagios

sudo vi /usr/local/nagios/etc/objects/commands.cfg

1234	define command { command_name notify-by-twitter command_line /usr/local/nagios/libexec/twitter.pl "$NOTIFICATIONTYPE$ -$HOSTNAME$-$SERVICEDESC$ - $SERVICESTATE$ - $SERVICEOUTPUT$"}

Then in the contacts.cfg, use this:

service_notification_commands notify-by-twitter

Reference: Twitter as Nagios notification gateway

Nagios 3: Install nrpe

2007-11-05T09:39:00Z

“NRPE: Nagios Remote Plugin Executor allows you to execute local plugins on remote hosts.”

1, Add user and group named ‘nagios’

/usr/sbin/useradd nagios

passwd nagios

2, compile nagios-plugin

download: http://sourceforge.net/project/showfiles.php?group_id=29880

tar zxvf nagios-pluginxxx.tar.gz
cd nagios-plugin
./configure
make
make install

chown nagios:nagios /usr/local/nagios
chown -R nagios:nagios /usr/local/nagios/libexec

3, compile nrpe

download: http://sourceforge.net/project/showfiles.php?group_id=26589

tar zxvf  nrpexxx.tar.gz
cd nrpe
./configure
make all
sudo make install-plugin
sudo make install-daemon
sudo make install-daemon-config

4, Start nrpe

vi /usr/local/nagios/etc/nrpe.cfg

allowed_hosts=127.0.0.1,123.12.1.2

123.12.1.2 is your nagios server address

start nagios:

/usr/local/nagios/bin/nrpe -c /usr/local/nagios/etc/nrpe.cfg -d

Check the nrpe on nagios server

/usr/local/nagios/libexec/check_nrpe -H 123.12.1.5

123.12.1.5 is the ip adress of the nrpe deamon(the remote pc)

You should see something like:

NRPE v2.9

Congratulate! your nrpe works now.