Adds a new mechanism to load providers from any gem or file path. (#263)

* Adds ability to load only providers used in config file

lib/vmpooler.rb

@@ -11,7 +11,7 @@ module Vmpooler
   require 'yaml'
   require 'set'
 
-  %w[api graphite logger pool_manager statsd dummy_statsd generic_connection_pool providers].each do |lib|
+  %w[api graphite logger pool_manager statsd dummy_statsd generic_connection_pool].each do |lib|
     require "vmpooler/#{lib}"
   end
 

lib/vmpooler/pool_manager.rb

@@ -1,3 +1,5 @@
+require 'vmpooler/providers'
+
 module Vmpooler
   class PoolManager
     CHECK_LOOP_DELAY_MIN_DEFAULT = 5
@@ -26,6 +28,9 @@ module Vmpooler
       @reconfigure_pool = {}
 
       @vm_mutex = {}
+
+      # load specified providers from config file
+      load_used_providers
     end
 
     def config
@@ -457,19 +462,36 @@ module Vmpooler
       result
     end
 
+    # load only providers used in config file
+    def load_used_providers
+      Vmpooler::Providers.load_by_name(used_providers)
+    end
+
+    # @return [Array] - a list of used providers from the config file, defaults to the default providers
+    # ie. ["vsphere", "dummy"]
+    def used_providers
+      pools = config[:pools] || []
+      @used_providers ||= (pools.map { |pool| pool[:provider] || pool['provider'] }.compact + default_providers ).uniq
+    end
+
+    # @return [Array] - returns a list of providers that should always be loaded
+    # note: vsphere is the default if user does not specify although this should not be
+    # if vsphere is to no longer be loaded by default please remove
+    def default_providers
+      @default_providers ||= %w( vsphere dummy )
+    end
+
     def get_pool_name_for_vm(vm_name)
       # the 'template' is a bad name.  Should really be 'poolname'
       $redis.hget('vmpooler__vm__' + vm_name, 'template')
     end
 
+    # @param pool_name [String] - the name of the pool
+    # @return [Provider] - returns the provider class Object
     def get_provider_for_pool(pool_name)
-      provider_name = nil
-      $config[:pools].each do |pool|
-        next unless pool['name'] == pool_name
-        provider_name = pool['provider']
-      end
-      return nil if provider_name.nil?
-
+      pool = $config[:pools].find { |pool| pool['name'] == pool_name }
+      return nil unless pool
+      provider_name = pool.fetch('provider', nil)
       $providers[provider_name]
     end
 

lib/vmpooler/providers.rb

@@ -1,7 +1,119 @@
-%w[base dummy vsphere].each do |lib|
-  begin
-    require "vmpooler/providers/#{lib}"
-  rescue LoadError
-    require File.expand_path(File.join(File.dirname(__FILE__), 'providers', lib))
+require 'pathname'
+
+module Vmpooler
+  class Providers
+
+    # @param names [Array] - an array of names or string name of a provider
+    # @return [Array] - list of provider files loaded
+    # ie. ["lib/vmpooler/providers/base.rb", "lib/vmpooler/providers/dummy.rb", "lib/vmpooler/providers/vsphere.rb"]
+    def self.load_by_name(names)
+      names = Array(names)
+      instance = self.new
+      names.map {|name| instance.load_from_gems(name)}.flatten
+    end
+
+    # @return [Array] - array of provider files
+    # ie. ["lib/vmpooler/providers/base.rb", "lib/vmpooler/providers/dummy.rb", "lib/vmpooler/providers/vsphere.rb"]
+    # although these files can come from any gem
+    def self.load_all_providers
+      self.new.load_from_gems
+    end
+
+    # @return [Array] - returns an array of gem names that contain a provider
+    def self.installed_providers
+      self.new.vmpooler_provider_gem_list.map(&:name)
+    end
+
+    # @return [Array] returns a list of vmpooler providers gem plugin specs
+    def vmpooler_provider_gem_list
+      gemspecs.find_all { |spec| File.directory?(File.join(spec.full_gem_path, provider_path)) } + included_lib_dirs
+    end
+
+    # Internal: Find any gems containing vmpooler provider plugins and load the main file in them.
+    #
+    # @return [Array[String]] - a array of provider files
+    # @param name [String] - the name of the provider to load
+    def load_from_gems(name = nil)
+      paths = gem_directories.map do |gem_path|
+        # we don't exactly know if the provider name matches the main file name that should be loaded
+        # so we use globs to get everything like the name
+        # this could mean that vsphere5 and vsphere6 are loaded when only vsphere5 is used
+        Dir.glob(File.join(gem_path, "*#{name}*.rb")).each do |file|
+          require file
+        end
+      end
+      paths.flatten
+    end
+
+    private
+
+    # @return [String] - the relative path to the vmpooler provider dir
+    # this is used when searching gems for this path
+    def provider_path
+      File.join('lib','vmpooler','providers')
+    end
+
+    # Add constants to array to skip over classes, ie. Vmpooler::PoolManager::Provider::Dummy
+    def excluded_classes
+      []
+    end
+
+    # paths to include in the search path
+    def included_lib_dirs
+      []
+    end
+
+    # returns an array of plugin classes by looking in the object space for all loaded classes
+    # that start with Vmpooler::PoolManager::Provider
+    def plugin_classes
+      unless @plugin_classes
+        load_plugins
+        # weed out any subclasses in the formatter
+        klasses = ObjectSpace.each_object(Class).find_all do |c|
+          c.name && c.name.split('::').count == 3 && c.name =~ /Vmpooler::PoolManager::Provider/
+        end
+        @plugin_classes = klasses - excluded_classes || []
+      end
+      @plugin_classes
+    end
+
+    def plugin_map
+      @plugin_map ||= Hash[plugin_classes.map { |gem| [gem.send(:name), gem] }]
+    end
+
+
+
+    # Internal: Retrieve a list of available gem paths from RubyGems.
+    #
+    # Returns an Array of Pathname objects.
+    def gem_directories
+      dirs = []
+      if has_rubygems?
+        dirs = gemspecs.map do |spec|
+          lib_path = File.expand_path(File.join(spec.full_gem_path,provider_path))
+          lib_path if File.exists? lib_path
+        end + included_lib_dirs
+      end
+      dirs.reject { |dir| dir.nil? }.uniq
+    end
+
+    # Internal: Check if RubyGems is loaded and available.
+    #
+    # Returns true if RubyGems is available, false if not.
+    def has_rubygems?
+      defined? ::Gem
+    end
+
+    # Internal: Retrieve a list of available gemspecs.
+    #
+    # Returns an Array of Gem::Specification objects.
+    def gemspecs
+      @gemspecs ||= if Gem::Specification.respond_to?(:latest_specs)
+                      Gem::Specification.latest_specs
+                    else
+                      Gem.searcher.init_gemspecs
+                    end
+    end
+
   end
 end

lib/vmpooler/providers/dummy.rb

@@ -1,4 +1,5 @@
 require 'yaml'
+require 'vmpooler/providers/base'
 
 module Vmpooler
   class PoolManager

lib/vmpooler/providers/vsphere.rb

@@ -1,3 +1,5 @@
+require 'vmpooler/providers/base'
+
 module Vmpooler
   class PoolManager
     class Provider