Replacement python_pip Chef provider that calls out to package index servers to get the latest version for candidate_version, reducing duplicate downloads and unneeded restarts.

pip.rb

#
# Author:: Seth Chisamore <schisamo@opscode.com>
# Cookbook Name:: python
# Provider:: pip
#
# Copyright:: 2011, Opscode, Inc <legal@opscode.com>
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
require 'uri'
require 'zlib'

require 'chef/mixin/shell_out'
require 'chef/mixin/language'
require 'chef/rest'
include Chef::Mixin::ShellOut

def whyrun_supported?
  true
end

# the logic in all action methods mirror that of
# the Chef::Provider::Package which will make
# refactoring into core chef easy

action :install do
  # If we specified a version, and it's not the current version, move to the specified version
  if new_resource.version != nil && new_resource.version != current_resource.version
    install_version = new_resource.version
    # If it's not installed at all, install it
  elsif current_resource.version == nil
    install_version = candidate_version
  end

  if install_version
    description = "install package #{new_resource} version #{install_version}"
    converge_by(description) do
      Chef::Log.info("Installing #{new_resource} version #{install_version}")
      status = install_package(install_version)
      if status
        new_resource.updated_by_last_action(true)
      end
    end
  end
end

action :upgrade do
  if current_resource.version != candidate_version
    orig_version = current_resource.version || "uninstalled"
    description = "upgrade #{current_resource} version from #{current_resource.version} to #{candidate_version}"
    converge_by(description) do
      Chef::Log.info("Upgrading #{new_resource} version from #{orig_version} to #{candidate_version}")
      status = upgrade_package(candidate_version)
      if status
        new_resource.updated_by_last_action(true)
      end
    end
  end
end

action :remove do
  if removing_package?
    description = "remove package #{new_resource}"
    converge_by(description) do
      Chef::Log.info("Removing #{new_resource}")
      remove_package(new_resource.version)
      new_resource.updated_by_last_action(true)
    end
  end
end

def removing_package?
  if current_resource.version.nil?
    false # nothing to remove
  elsif new_resource.version.nil?
    true # remove any version of a package
  elsif new_resource.version == current_resource.version
    true # remove the version we have
  else
    false # we don't have the version we want to remove
  end
end

# these methods are the required overrides of
# a provider that extends from Chef::Provider::Package
# so refactoring into core Chef should be easy

def load_current_resource
  @current_resource = Chef::Resource::PythonPip.new(new_resource.name)
  @current_resource.package_name(new_resource.package_name)
  @current_resource.version(nil)

  unless current_installed_version.nil?
    @current_resource.version(current_installed_version)
  end

  @current_resource
end

def current_installed_version
  @current_installed_version ||= begin
    delimeter = /==/

    version_check_cmd = "#{which_pip(new_resource)} freeze | grep -i '^#{new_resource.package_name}=='"
    # incase you upgrade pip with pip!
    if new_resource.package_name.eql?('pip')
      delimeter = /\s/
      version_check_cmd = "#{which_pip(@new_resource)} --version"
    end
    result = shell_out(version_check_cmd)
    (result.exitstatus == 0) ? result.stdout.split(delimeter)[1].strip : nil
  end
end

def candidate_version
  version = 'latest'
  [node[:python][:index_url], node[:python][:extra_index_url]].each do |site|
    url = URI.parse("#{site}/#{new_resource.package_name}/")
    response = Chef::REST::RESTRequest.new('GET', url, '').call
    if response.kind_of?(Net::HTTPSuccess)
      body = decompress_body(response)
      matches = body.scan(/<a href=".*">\w+-(?<version>[\d.]+).tar.gz<\/a>/)
      versions = matches.flatten.sort
      version = versions.pop || 'latest'
      break
    end
  end
  Chef::Log.info("Candidate version: #{version}")
  version
end

def install_package(version)
  # if a version isn't specified (latest), is a source archive (ex. http://my.package.repo/SomePackage-1.0.4.zip),
  # or from a VCS (ex. git+https://git.repo/some_pkg.git) then do not append a version as this will break the source link
  if version == 'latest' || new_resource.package_name.downcase.start_with?('http:', 'https:') || ['git', 'hg', 'svn'].include?(new_resource.package_name.downcase.split('+')[0])
    version = ''
  else
    version = "==#{version}"
  end
  pip_cmd('install', version)
end

def upgrade_package(version)
  new_resource.options "#{new_resource.options} --upgrade"
  install_package(version)
end

def remove_package(version)
  new_resource.options "#{new_resource.options} --yes"
  pip_cmd('uninstall')
end

def pip_cmd(subcommand, version='')
  options = { :timeout => new_resource.timeout, :user => new_resource.user, :group => new_resource.group }
  environment = Hash.new
  environment['HOME'] = Dir.home(new_resource.user) if new_resource.user
  environment.merge!(new_resource.environment) if new_resource.environment && !new_resource.environment.empty?
  options[:environment] = environment
  shell_out!("#{which_pip(new_resource)} #{subcommand} #{new_resource.options} #{new_resource.package_name}#{version}", options)
end

# TODO remove when provider is moved into Chef core
# this allows PythonPip to work with Chef::Resource::Package
def which_pip(nr)
  #if (nr.respond_to?("virtualenv") && nr.virtualenv)
  #  ::File.join(nr.virtualenv,'/bin/pip')
  #elsif ::File.exists?(node['python']['pip_location'])
  #  node['python']['pip_location']
  #else
  'pip'
  #end
end


def decompress_body(response)
  if response.body.nil?
    response.body
  else
    case response['content-encoding']
      when 'gzip'
        Chef::Log.debug "decompressing gzip response"
        Zlib::Inflate.new(Zlib::MAX_WBITS + 16).inflate(response.body)
      when 'deflate'
        Chef::Log.debug "decompressing deflate response"
        Zlib::Inflate.inflate(response.body)
      else
        response.body
    end
  end
end