Posted by Dan Sosedoff
on June 15, 2010
Amazon has an awesome image service. You can use their product images on your site, adjusting them for you needs. All you have to know – one image url of your product. Having that string will provide you an access to its dynamic image scaling service which i had to use recently.
So, lets say you have books on your website, but you dont have any good images for them. There is 2 ways to solve your problem: 1) download it from whatever place and resize 2) use amazon!
Here goes small overview.
Unfortunately, i didnt have any time to play with image service for different countries, but i assume that wont change that much. Lets take a look on a regular image:
http://ecx.images-amazon.com/images/I/41ygBmdaIfL._SL500_SS100_.jpg
It has different parts:
1) URL base: http://ecx.images-amazon.com/images/I/
2) Image code: 41ygBmdaIfL
3) Size format (surrounded by underscores): _SL500_SS100_
4) Format: jpg/gif/png
Some words about image format. It can vary from square thumbnails to images with specific max width and height. For example: _SX100_ will produce image that 100 pixels wide, height will be calculated proportionally. SH100 will give opposite result, scaled by 100 pixels maximum height, SS100 – 100×100 pixels thumbnail. And so on, you can find other similar crop codes while exploring amazon store on different pages, all you need is to take a look on image sources.
Now, we need to use this with Ruby:
require 'net/http'
module Amazon
# parse amazon image url and get image code and extension
def self.parse_image(url)
result = url.scan(/^http:\/\/ecx.images-amazon.com\/images\/I\/([a-z0-9\-\%]{1,})(.*)_.(jpg|jpeg|gif)/i)
unless result.nil?
unless result[0].nil?
match = result.first
return {:code => match.first.to_s, :extension => match.last.to_s}
end
end
end
# make a new amazon image url based on code and size
def self.make_image(image, size)
"http://ecx.images-amazon.com/images/I/#{image[:code]}._#{size.upcase}.#{image[:extension]}"
end
# check if actual image exists
def self.check_image(url)
begin
uri = URI.parse(url)
req = Net::HTTP::Get.new(uri.path)
res = Net::HTTP.start(uri.host, uri.port) { |http| http.request(req) }
return res.code == '200' && res.content_length.to_i > 0
rescue Exception
false
end
end
endAnd usage:
url = 'http://ecx.images-amazon.com/images/I/51O65dIoZCL._SX117_.jpg'
info = Amazon.parse_image(url)
unless info.nil?
new_url = Amazon.make_image(info, 'sx100')
if Amazon.check_image(new_url)
puts "Cool! Resized image: #{new_url}"
else
puts "Sorry, this image does not exist!"
end
else
puts "Cant identify image!"
endSome notes about the process. The only reason why method “check_image” uses GET method instead of HEAD is because if image cannot be generated or not found in amazon`s cache the response is still valid sometimes. I`ve checked it on 50k images and sometimes HEAD request indicates that response is valid while it not supposed to. Otherwise i would use HEAD.
Posted by Dan Sosedoff
on June 13, 2010
While working on one of the projects, i tried to find multi-purpose HTTP request class that can use different network interfaces/ip addresses with retry option (if connection slow or server not responding for some reason).
Here is a small class wrapper build on top of Ruby Curb implemented as a module:
module ApiRequest
USER_AGENTS = [
'Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.2.3) Gecko/20100401 Firefox/3.6.3',
'Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 2.0.50727)',
'Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.3) Gecko/20100423 Ubuntu/10.04 (lucid) Firefox/3.6.3',
'Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_3; en-US) AppleWebKit/533.4 (KHTML, like Gecko) Chrome/5.0.375.70 Safari/533.4',
'Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.2) Gecko/20100323 Namoroka/3.6.2',
'Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.9) Gecko/20100401 Ubuntu/9.10 (karmic) Firefox/3.5.9'
]
CONNECTION_TIMEOUT = 10
@@interfaces = []
# get random user-agent string for usage
def random_agent
USER_AGENTS[rand(USER_AGENTS.size-1)]
end
# get random IP/network interface specified in @@interfaces
def random_interface
size = @@interfaces.size
size > 0 ? @@interfaces[rand(size-1)] : nil
end
# perform request, assign_to - specify network interface/ip
def perform(url, assign_to=nil)
puts url
interface = assign_to.nil? ? self.random_interface : assign_to
req = Curl::Easy.new(url)
req.timeout = CONNECTION_TIMEOUT
req.interface = interface unless interface.nil?
req.headers['User-Agent'] = self.random_agent
begin
req.perform
if req.response_code == 200
return req.downloaded_bytes > 0 ? req.body_str : nil
else
nil
end
rescue Exception
return nil
end
end
# perform request by number of attempts
def fetch(url, attempts=3)
result = nil
1.upto(attempts) do |a|
result = self.perform(url)
break unless result.nil?
end
return result
end
endAnd sample usage:
class TestRequest
include ApiRequest
def foo
body = self.fetch('http://google.com')
end
endIf module variable “@@interfaces” is array of ip addresses or network interfaces then one of them (randomly selected) will be used to perform request. Also, function “fetch” has parameter “attempts” which set to 3 by default. It means that operation will be invoked n times until result is downloaded from url. Otherwise – it returns nil.
Function perform has a parameter “assign_to” (which it not used in “fetch” function) that allows to bind request to specified interface. It is useful if you have situation when you might use different workers that bound to exact interface or just one that uses random ip`s. Also, class ApiRequest has a list of user agents which it uses randomly for each performed request.
Pastie: http://pastie.org/private/j19j3hbebte9bjqaydslmg
Posted by Dan Sosedoff
on June 09, 2010
At some point you will find that you have reached requests per IP limit while using some API or crawling resources. And if you`re doing it via standard Net::HTTP you`ll face the problem that you cannot assign request class to specified network interface (or IP). Bummer? No. Even if you cant do it with core class you might take a look on Curb – libcurl ruby binding. It has everything that you need to make regular get/post/etc requests. And of course – easy.
A simple example (real ip`s are changed):
require 'rubygems'
require 'curb'
ip_addresses = [
'1.1.1.1',
'2.2.2.2',
'3.3.3.3',
'4.4.4.4',
'5.5.5.5'
]
ip_addresses.each do |ip|
req = Curl::Easy.new('http://www.ip-adress.com/')
req.interface = ip
req.perform
result_ip = req.body_str.scan(/<h2>My IP address is: ([\d\.]{1,})<\/h2>/).first
puts("for #{ip} got response: #{result_ip}")
endOutput (ip`s are changed):
for 1.1.1.1 got response: 1.1.1.1
for 2.2.2.2 got response: 2.2.2.2
for 3.3.3.3 got response: 3.3.3.3
for 4.4.4.4 got response: 4.4.4.4
for 5.5.5.5 got response: 5.5.5.5
At least its working. Havent done any performance tests.
Sample on pastie: http://pastie.org/private/afxlcuk1npwjov3wer5hw
Posted by Dan Sosedoff
on May 02, 2009
Here is a simple example how to make native WebDAV client with Ruby sockets. No additional gems or extensions needed – just all basic classes.
class WebDAV
attr_reader :host, :port, :protocol, :chunk_size
@socket = nil
def initialize(host,port=80,protocol='HTTP/1.1',chunk=8096)
@host = host.to_s
@port = port.to_i
@protocol = protocol
@chunk_size = chunk.to_i
end
def build_header(method, path, content_length=nil)
header = "#{method} #{path} #{@protocol} \r\n"
header += "Content-Length: #{content_length}\r\n" if !content_length.nil?
header += "Host: #{@host}\r\n"
header += "Connection: close\r\n\r\n"
return header
end
def request(method, path)
open
header = build_header(method, path)
if @socket.write(header) == header.length then
return @socket.gets.split[1]
end
end
def delete(path)
request('DELETE', path)
end
def head(path)
request('HEAD', path)
end
def mkcol(path)
request('MKCOL', path)
end
def put(path, localfile, auto_head=true)
if !File.exists?(localfile) || !File.readable?(localfile)
raise "File not exists or not accessible for reading!"
end
open
datalen = File.size(localfile)
header = build_header('PUT', path, datalen)
begin
if @socket.write(header) == header.length then
written = 0
File.open(localfile,'r') do |f|
until f.eof? do
written += @socket.write(f.read(@chunk_size))
end
end
if written == datalen
close
if !auto_head
return true
else
return head(path)
end
end
end
rescue Exception => e
puts e
return false
end
end
def open
begin
@socket = TCPSocket.open(@host,@port)
return true
rescue Exception => e
puts e
return false
end
end
def close
begin
return @socket.close
rescue
return false
end
end
endThis class supports only basic http/dav methods (PUT, DELETE, MKCOL, HEAD) and can be extended very easily and designed to work with all files, reading them by small chunks (default is 8096 bytes).
Im using this class sometimes with nginx.
Deps:
require 'socket'
require 'digest'
Usage:
# create connection
conn = WebDAV.new('your.host.com')
# upload file (without autocheck), return true/false value
result = conn.put('/test.mp3','/home/.../..../..../file.mp3', false)
# upload file with autocheck, returns http response code (201, 404, ... ) so you`ll know what exactly happened
result = conn.put('/test2.mp3','/home/.../file.mp3')Also, here is a wrapper class to produce MD5, SHA1 file hashes that supports big files.
class FileHash
def self.md5(path)
d = Digest::MD5.new
File.open(path,'r') do |f|
d.update(f.read(8192)) until f.eof?
end
return d.hexdigest
end
def self.sha1(path)
d = Digest::SHA1.new
File.open(path,'r') do |f|
d.update(f.read(8192)) until f.eof?
end
return d.hexdigest
end
end
Usage:
FileHash.md5('/path/to/file')
FileHash.sha1('/path/to/file')This webdav class not pretending to be stable in production environment, but can be useful for some “one-time” tasks with less code.
Posted by Dan Sosedoff
on March 22, 2009
For a long time i was thinking that Amazon`s Simple Storage Service (S3) is very complicated thing. But, it was before i tried it. Couple days ago, i got account to S3 and started exploring API`s and architecture. Now i see how stupid i was 
It`s really easy to handle all operations with files and buckets. Pricing also comfortable.
Welcome to cloud computing! I started using it with Ruby. Regular gem and docs can be found at http://amazon.rubyforge.org/
So, the first useful tool i decided to created – simple uploader of local files to amazons server.
First, we need to create bucket and make it public:
Bucket.create('NAME_HERE',:access => :public_read)Here`s the client ruby script:
#!/usr/bin/ruby
require 'rubygems'
require 'aws/s3'
include AWS::S3
$s3_bucket = "BUCKET_NAME"
$s3_key = "API_KEY"
$s3_secret = "API_SECRET"
def s3_store(localfile)
if File.exists?(localfile) && File.readable?(localfile)
puts "Uploading file [#{localfile}]. Size: #{File.size(localfile)} bytes."
name = File.basename(localfile)
Base.establish_connection!(:access_key_id => $s3_key, :secret_access_key => $s3_secret)
S3Object.store(name, open(localfile), $s3_bucket, :access => :public_read)
puts "Download link: http://s3.amazonaws.com/#{$s3_bucket}/#{name}"
else
puts "File not exists or not accessible. Please check file and try again!"
end
end
path = ARGV[0]
if !path
"Please specify the file to upload."
else
s3_store(path)
endDownload script: http://files.sosedoff.com/036cfedd/
BTW, I found cool firefox add-on to manage S3 objects/files. It`s pretty easy.
Link to extension – http://www.s3fox.net
Screenshot:
Posted by Dan Sosedoff
on February 15, 2009
As previous post was about fetching covers media from Amazon Web Services, this post will be about fetching covers from popular music site – Last.fm. API documentation page
#!/usr/bin/ruby
require 'rubygems'
require 'net/http'
require 'cgi'
require 'xmlsimple'
# key from API documentation
$lastfm_key = "b25b959554ed76058ac220b7b2e0a026"
$lastfm_host = "ws.audioscrobbler.com"
def fetch_cover(artist, album)
artist = CGI.escape(artist)
album = CGI.escape(album)
path = "/2.0/?method=album.getinfo&api_key=#{$lastfm_key}&artist=#{artist}&album=#{album}"
data = Net::HTTP.get($lastfm_host, path)
xml = XmlSimple.xml_in(data)
if xml['status'] == 'ok' then
album = xml['album'][0]
cover = {
:small => album['image'][1]['content'],
:medium => album['image'][2]['content'],
:big => album['image'][3]['content']
}
return cover
end
return nil
end
puts fetch_cover('Nickelback', 'Dark Horse').inspectDownload ruby script
Posted by Dan Sosedoff
on February 15, 2009
On my small project i was looking for web service to get media covers from. I found that i can use Amazon Web Services API. The documentation for this ECommerce Service is pretty old, but it still works.
More detailed information about API you can find here
#!/usr/bin/ruby
require 'rubygems'
require 'net/http'
require 'cgi'
require 'xmlsimple'
$amazon_key = "12DR2PGAQT303YTEWP02" # NOT MY KEY (FOUND ON INTERNET)
$amazon_host = "webservices.amazon.com"
def fetch_cover(artist, album)
artist = CGI.escape(artist)
album = CGI.escape(album)
path = "/onca/xml?Service=AWSECommerceService&AWSAccessKeyId=#{$amazon_key}&Operation=ItemSearch&SearchIndex=Music&Artist=#{artist}&ResponseGroup=Images&Keywords=#{album}"
data = Net::HTTP.get($amazon_host, path)
xml = XmlSimple.xml_in(data)
if xml['Items'][0]['TotalResults'].to_s.to_i then
cover = {
:small => xml['Items'][0]['Item'][0]['SmallImage'][0]['URL'],
:medium => xml['Items'][0]['Item'][0]['MediumImage'][0]['URL'],
:big => xml['Items'][0]['Item'][0]['LargeImage'][0]['URL']
}
return cover
end
return nil
endSo, after execution of this function you will get array with 3 different images (small, medium, big).
I use XML-Simple gem for ruby. Can be installed this way
sudo gem install xml-simple
That`s it. Download script
